Drill control scheme. Power tool engine speed controller - diagram and principle of operation

Probably, there is no such person who would not have heard about the existence of an electric drill. Many even used it, but not many people know the device of the drill and the principle of operation. This article will help fill this gap.

Drill device (the simplest Chinese electric drill): 1 - speed controller, 2 - reverse, 3 - brush holder with a brush, 4 - motor stator, 5 - impeller for cooling the electric motor, 6 - gearbox.

electric motor. The commutator electric motor of a drill contains three main elements - a stator, an armature and carbon brushes. The stator is made of electrical steel with high magnetic permeability. It has a cylindrical shape and grooves for laying stator windings. There are two stator windings and they are located opposite each other. The stator is rigidly fixed in the drill body.

Drill device: 1 - stator, 2 - stator winding (second winding under the rotor), 3 - rotor, 4 - rotor collector plates, 5 - brush holder with brush, 6 - reverse, 7 - speed controller.

The rotor is a shaft onto which a core of electrical steel is pressed. Grooves are machined along the entire length of the core, through an equal distance, for laying anchor windings. The windings are wound with a solid wire with taps for fastening to the collector plates. Thus, an anchor is formed, divided into segments. The collector is located on the shaft shank and is rigidly fixed on it. During operation, the rotor rotates inside the stator on bearings located at the beginning and end of the shaft.

Spring-loaded brushes move along the plates during operation. By the way, when a drill is being repaired, you should Special attention give it to them. The brushes are pressed from graphite, they look like a parallelepiped with built-in flexible electrodes.

speed controller. The speed of the drill is controlled by a triac controller located in the power button. It should be noted a simple adjustment scheme and a small number of parts. This regulator is assembled in a button case on a textolite substrate using microfilm technology. The board itself has a miniature size, which made it possible to place it in the trigger housing. The key point is that in the drill controller (in the triac) the circuit breaks and closes in milliseconds. And the regulator does not change the voltage that comes from the outlet in any way ( however, the rms value of the voltage changes, which is shown by all voltmeters measuring alternating voltage). More precisely, there is a pulse-phase control. If the button is pressed lightly, then the time when the circuit is closed is the smallest. As you press, the time the circuit is closed increases. When the button is pressed to the limit, the time when the circuit is closed is maximum or the circuit is not opened at all.

More scientifically, it looks like this. The principle of operation of the regulator is based on changing the moment (phase) of switching on the triac (closing the circuit) relative to the transition of the mains voltage through zero (the beginning of a positive or negative half-wave of the supply voltage).

Voltage diagrams: in the network (at the input of the regulator), at the control electrode of the triac, at the load (at the output of the regulator).

To make it easier to understand the operation of the regulator, we will build three time voltage diagrams: network voltage, on the control electrode of the triac and on the load. After the drill is connected to the network, an alternating voltage is supplied to the input of the regulator (upper diagram). At the same time, a sinusoidal voltage is applied to the control electrode of the triac (middle diagram). At the moment when its value exceeds the triac turn-on voltage, the triac will open (the circuit will close) and the mains current will flow through the load. After the value of the control voltage falls below the threshold, the triac remains open due to the fact that the load current exceeds the holding current. At the moment when the voltage at the input of the regulator changes its polarity, the triac closes. Then the process is repeated. Thus, the voltage across the load will have the shape of the diagram below.

The greater the amplitude of the control voltage, the earlier the triac will turn on, and therefore, the duration of the current pulse in the load will be longer. Conversely, the smaller the amplitude of the control signal, the shorter will be the duration of this pulse. The amplitude of the control voltage is controlled by a variable resistor connected to the drill trigger. It can be seen from the diagram that if the control voltage is not phase shifted, the control range will be from 50 to 100%. Therefore, in order to expand the range, the control voltage is shifted in phase, and then during the processes of pressing the trigger, the voltage at the output of the regulator will change as shown in the figure below.

It is shown how the voltage at the output of the regulator will change if you press the trigger of the drill.

The wire connection diagram, and in particular the drill button connection diagram, may differ in different models. The simplest circuit, and best of all demonstrating the principle of operation, is as follows. One lead from the power cord is connected to the speed controller.

Drill electric circuit. "reg. rev." - electric drill speed controller, "1st stage of exchange." - the first stator winding, "2nd stage exchange." - the second stator winding, "1st brush." - first brush, "2nd brush." - the second brush.

In order not to be confused, it is important to understand that the speed controller and the reverse control device are two different parts that often have different housings.

The speed controller and reverse are in separate housings. The photo shows that only two wires are connected to the speed controller.

The only wire coming out of the speed controller is connected to the beginning of the first stator winding. If there were no reverse device, the end of the first winding would be connected to one of the rotor brushes, and the second rotor brush would be connected to the beginning of the second stator winding. The end of the second stator winding leads to the second wire of the power cord. That's the whole scheme.

A change in the direction of rotation of the rotor occurs when the end of the first stator winding is connected not to the first, but to the second brush, while the first brush is connected to the beginning of the second stator winding.

In the reverse device, such switching occurs, therefore the rotor brushes are connected to the stator windings through it. There may be a diagram on this device showing which wires are connected internally.

The scheme on the reverse of the electric drill (in the photo, the reverse is disconnected from the speed controller)

Black wires lead to the rotor brushes (let the 5th contact be the first brush, and let the 6th contact be the second brush), gray wires - to the end of the first stator winding (let it be the 4th contact) and the beginning of the second (let it be 7- th contact). With the switch position shown in the photo, the end of the first stator winding with the first rotor brush (4th with 5th), and the beginning of the second stator winding with the second rotor brush (7th with 6th) are closed. When switching the reverse to the second position, the 4th is connected to the 6th, and the 7th to the 5th.

The design of the electric drill speed controller provides for the connection of a capacitor and the connection to the controller of both wires coming from the outlet. The diagram in the figure below, for a better understanding, is slightly simplified: there is no reverse device, the stator windings are not yet shown, to which the wires from the regulator are connected (see diagrams above).

In the case of the described electric drill, only two lower contacts are used: the extreme left and the extreme right. There is no capacitor, and the second wire of the power cord is connected directly to the stator winding.

Reducer. The drill reducer is designed to reduce the speed of the drill and increase the torque. The most common gear reducer with one gear. There are also drills with several gears, for example two, while the mechanism itself is somewhat reminiscent of a car gearbox.

Drill impact. Some drills have an impact mode for chiseling holes in concrete walls. To do this, a wavy "washer" is placed on the side of the large gear, and the same "washer" is opposite.

When drilling with the impact mode turned on, when the drill rests against, for example, a concrete wall, the wavy "washers" touch and, due to their undulations, imitate impacts. "Washers" wear out over time, and require replacement.

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An electric drill is now present in the tool kit of almost any master, as it is an indispensable unit in everyday life or in the professional field. But, like any part, a drill can break down and, in order not to turn to specialists every time, you need to be able to maintain and repair your tool yourself. This article discusses the signs of a breakdown and options for eliminating them, as well as the most common malfunctions and how to repair a drill with your own hands.

The drill belongs to electric tools and performs the functions of drilling holes in various materials, as well as tightening self-tapping screws. The work is carried out using special drills and tips that are inserted into the chuck.

The electric drill is equipped with a motor driven by a current of 220 volts, which rotates the transmission gears and other components. The power of the power unit is adjusted by a special regulator, which is located on the start button and rotates in both directions. Some models are equipped with a rotation axis switch that changes the location of the brushes, from its drill chuck it can turn both to the right and to the left.

There are two types of chuck: slotted and smooth. In the first case, the drill is clamped with a special key, which, when turned, twists the lower part of the head and fixes the part. A conventional smooth chuck can only be screwed by hand, so if you need to clamp the drill tightly, a slotted chuck has an advantage.

The main types of electric drill malfunction

Any tool can suddenly break down, this is due to improper operation, violation of the regulations Maintenance or just careless attitude to technology. In order to prevent the occurrence of a breakdown, it is necessary to follow all the rules established by the manufacturer, as well as to repair and replace parts that have expired in time.

There are several varieties possible faults household electric drills, which include:

1. When the start button is pressed, the drill does not work. First of all, in this case it is necessary to check the quality of the contact between the plug and the socket, as well as the presence of electricity. Most often, such a malfunction occurs due to burnt contacts inside the plug or in the cord itself, when a wire break is formed as a result of a load or current drop. This problem is solved by simply replacing the lead cable;

1. The drill chuck rotates, but the speed of revolutions is unchanged. Here it can be assumed that the drill speed controller is faulty, which can break due to mechanical deformation or dirt on the roller. A contactor is built inside the regulator, which can burn out, and it can be repaired only by replacing the assembly completely, since soldering such a small part at home will not work. In general, for a drill with a speed control mechanism, this is the most vulnerable part, so it must be treated with the utmost responsibility;
2. When starting, an unpleasant smell of burning appears from the ventilation hole of the brushes, the motor rotor sparks. The first thing to do is turn off the device and unplug the cord from the outlet, otherwise it will be much more difficult to repair an electric drill. Next, you need to carefully inspect the engine, determine the level of wear of the brushes and the rotor itself, and also check for foreign objects or other contaminants inside that interfere with the rotation of the rod;

1. A crunch in the central part of the instrument. All mechanisms and gears are hidden behind a plastic case, so it will not be possible to immediately determine the broken part. Most often, the splines of the drive disk break, especially for a drill with a hammer function, which, in addition to the usual transmission, has an impact mechanism and a blocking device. To replace these elements, you will need a complete disassembly of the tool and a detailed troubleshooting. It is important not to use a broken drill, as the broken pieces can fall into other nodes, which, when rotated, will completely destroy the mechanism, and it will not be possible to restore it;

1. The chuck does not fix the drill, the clamping tabs do not converge during tightening with a wrench. Most often, this malfunction can be eliminated very quickly, the cartridge itself is attached to the body of the drill with an ordinary screw, the cap of which is located inside the head and can be unscrewed from vibration. As a result, the bolt prevents the petals from pulling the drill, it must be tightened by inserting a curly screwdriver;
2. On an impact drill, the drill is inserted into a special chuck equipped with a quick-release mechanism, often pieces of metal or concrete get inside this unit, which clog into small cracks and prevent the latch from getting into its socket, so the inserted chuck constantly pops out of the hole. Detailed cleaning of the instrument and removal of all contaminants will help here.

These malfunctions are the most common and often occur during the use of an electric drill in everyday life. If more serious breakdowns occur, to restore the tool without errors, it is better to contact a service center, since without some experience and repair instructions, it will not be possible to fix the breakdown.

Brush cleaning and replacement

During operation, especially in difficult conditions, plaque forms on the brushes, and the electric drill begins to heat up and spark. To fix the drill with your own hands, by replacing the brushes with new ones, you must follow a certain algorithm of actions.

The first step is to unscrew the screws at the back of the motor. For ease of service, most tool manufacturers make this part so that it can be quickly removed without disassembling the main body, and the start button remains in place. After unscrewing the cover, it is completely removed, while the motor brushes and its rotor become accessible for maintenance.

Next, you need to disconnect the wire terminals from the carbon brushes and, having unbent the locking petals, pull the element out. The power unit is equipped with two brushes on both sides, which wear out at the same time, so they must be replaced together. By the level of tip wear, you can understand the state of the rotor bearings. If the wear is located in the upper or lower corner of the carbon rectangle, then it can be concluded that there is play in the motor armature bearing, this part must also be replaced.

Before installing new brushes for a drill, it is necessary to blow out all the internal elements with compressed air, this will help clean the rotor from dust and prevent plaque from forming on new parts. The button must also be cleaned so that its return spring has free play. The brushes are inserted into the seat and fixed with a lock, after which the terminals are connected, and the cover is reassembled.

If it is necessary to replace the start button or the speed controller, then it is possible to repair this assembly only if there is a connection diagram for the drill button, which should be indicated in the instruction manual for the tool. Connection of all electrical parts and cables must be carried out in a de-energized area and only in accordance with the diagram.

Thus, when planning to repair an electric drill on your own, you need to acquire special literature and tools so that there are no doubts about the quality of electrical connections when installing new spare parts.

Video

Drill - a manual, pneumatic or electric tool designed to impart rotational motion to a drill or other cutting tool for drilling holes in various materials during construction work

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What is the wiring diagram for the drill button?

Of course, it is impossible to state so unequivocally that the buttons on all drills are connected in the same way, there are drills with reverse, there is a direct connection, so this answer will be more informative than carrying specific information.

Even on drills of the same type, there is a difference in connecting a button depending on the functionality of the drills, here is an example of connecting an old Soviet drill:

Another connection scheme for a drill with a reverse, more or less generally accepted:

On some reversible drills, the following contacts are principally used on the button:

The upper part of the button interrupts the pole on the electric motor.

Here are a few diagrams for connecting drill buttons

(bottom photo is a diagram, connecting the button of an impact drill), the diagrams are drawn by hand, because the original circuits usually come with a power tool (a drill in this case).

If you are looking for something universal suitable for all types of drills, then this does not happen.

Drills are different in type, in power (by the way, when buying a new drill button, you must take into account the power of the tool, otherwise the button will not last long).

The drill can be with or without reverse (the button with reverse has an additional lever with which the drill switches to reverse rotation).

There is a professional tool, there is a domestic use.

That is, in order to find the scheme of the drill button (connection), it is necessary to build on a specific model of the drill.

Replacing the drill button, or repairing it, is carried out only when the electric drill is turned off.

If you have an old Soviet drill, then it is extremely difficult to find the original (native) circuit.

Since at present almost all drills are equipped with a reverse system, I will give a connection diagram in this way

I think that for those who understand circuit diagrams this figure will not be difficult and disconnection, by the way, too. I can only give one advice about the button, do not try to disassemble it, as usually it just shatters into many parts, which can then be very difficult to put together. In the case of a problem with a button, it is easier to change it than to repair it.

The standard scheme for connecting a drill with a reverse in the picture.

It shows the existing speed controller of the electric motor with the rotor reverse speed controller, reverse. The button is quite complex in design.

To connect the button, special knowledge is not needed, it is enough to know that the new button matches the power of the drill and the size.

Do-it-yourself drill repair

Failure of engine elements (stator, armature) - wear of brushes or their burning - failure of the regulator and reverse switch - wear of support bearings

Drill device (the simplest Chinese electric drill): 1 - speed controller, 2 - reverse, 3 - brush holder with a brush, 4 - motor stator, 5 - impeller for cooling the electric motor, 6 - gearbox.

Some spare parts (switch, rotor, stator, brushes, bearings, etc.) for the most popular models can be bought here (only it is better to buy through the online store, because the price may be higher in a regular store of this network).

Brush replacement. The most common type of breakdown is the wear of the motor brushes, which can be replaced independently at home. Sometimes, the brushes can be replaced without dismantling the drill body. For some models, it is enough to unscrew the plugs from the installation windows and install new brushes. For other models, replacement requires disassembly of the housing, in which case it is necessary to carefully remove the brush holders and remove the worn brushes from them.

Don't wait for the brushes to wear out minimum size. This is fraught with the fact that the gap between the brush and the collector plates increases. As a result, increased sparking occurs, the collector plates become very hot and can “move away” from the base of the collector, which will lead to the need to replace the armature.

You can determine the need to replace the brushes by increased sparking, which is visible in the ventilation slots of the housing. The second way to determine this is the chaotic "twitching" of the drill during operation.

Network cord. The cord is checked with an ohmmeter, one probe is connected to the contact of the power plug, the other to the core of the cord. The absence of resistance indicates a break. In this case, the repair of the drill comes down to replacing the mains wire.

Motor diagnostics. In second place, in terms of the number of drill breakdowns, you can put a malfunction of the engine elements and most often the anchor. The failure of the armature or stator occurs for two reasons - improper operation and poor-quality winding wire. World-famous manufacturers use expensive winding wire with double insulation with heat-resistant varnish, which significantly increases the reliability of engines. Accordingly, in cheap models, the quality of the winding wire insulation leaves much to be desired. Improper operation is reduced to frequent overloads of the drill or prolonged work, without interruptions to cool the engine. Do-it-yourself drill repair by rewinding the armature or stator, in this case it is impossible without special tools. Only a complete replacement of the element (exceptionally experienced repairmen will be able to rewind the armature or stator with their own hands).

You can determine the malfunction of the armature by a characteristic smell, an increase in sparking, while the sparks have a circular motion in the direction of movement of the armature. Pronounced "burnt" windings can be seen during visual inspection. But if the engine power has dropped, but there are no signs described above, then you should resort to the help of measuring instruments - an ohmmeter and a megohmmeter.

The windings (stator and armature) are subject to only three damages - an inter-turn electrical breakdown, a breakdown to the “case” (magnetic circuit) and a winding break. The breakdown on the case is determined quite simply, it is enough to touch any output of the winding and the magnetic circuit with the probes of the megohmmeter. Resistance over 500MΩ indicates no breakdown. It should be borne in mind that measurements should be carried out with a megohmmeter, in which the measuring voltage is not less than 100 volts. By making measurements with a simple multimeter, it is impossible to determine for sure that there is no breakdown, but you can determine that there is definitely a breakdown.

Speed ​​controller and reverse. The presence of voltage at the input terminals of the power button and the absence of voltage at the output indicates a malfunction of the contacts or components of the speed controller circuit. To disassemble the button, you can carefully pick up the latches of the protective cover and pull it off the button body. Visual inspection of the terminals will allow you to judge their performance. Blackened terminals are cleaned of soot with alcohol or fine sandpaper. Then the button is assembled again and checked for contact, if nothing has changed, then the button with the regulator must be replaced. The speed controller is made on a substrate and is completely filled with an insulating compound, therefore it cannot be repaired. Another characteristic malfunction of the button is the erasing of the working layer under the rheostat slider. The easiest way out is to replace the entire button.

When buying a new speed controller, you should make sure that it is rated for the power of the drill, so if the power of the drill is 750W, the controller must be rated for a current of more than 3.4A (750W/220V=3.4A). And by the way, the regulator on the drill in the photo is not native, and in order for it to fit into the case, the lower part of the trigger was cut off.

The bottom of the trigger has been cut off.

Drill electric circuit. "reg. rev." - electric drill speed controller, "1st stage of exchange." - the first stator winding, "2nd stage of exchange." - the second stator winding, "1st brush." - first brush, "2nd brush." - the second brush.

Drill reverse circuit

The scheme on the reverse of the electric drill (in the photo, the reverse is disconnected from the speed controller)

Wiring diagram for reverse electric drill

In the case of the electric drill shown in the photo, only two lower contacts are used: the extreme left and the extreme right. There is no capacitor, and the second wire of the power cord is connected directly to the stator winding.

Connecting an electric drill button

Read about the principle of operation of the speed controller in the article drill device.

Reducer. The presence of extraneous sounds, rattle and wedging of the cartridge indicates a malfunction of the gearbox or gear shift mechanism, if any. In this case, it is necessary to inspect all gears and bearings. If worn splines or broken teeth on the gears are found, then a complete replacement of these elements is necessary.

Bearings are checked for suitability after removing them from the armature axis or drill body using special pullers. Clamping the inner clip with two fingers, you need to scroll the outer clip. Uneven slippage of the cage or “rustling” when scrolling indicates the need to replace the bearing. An incorrectly replaced bearing will lead to anchor jamming, or, at best, the bearing will simply rotate in the seat.

Drill chuck replacement. The cartridge is subject to wear, namely the clamping “sponges”, due to the ingress of dirt and abrasive residues of building materials into it. If the chuck is to be replaced, unscrew the fixing screw inside the chuck (left-hand thread) and unscrew it from the shaft.

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Electric drill: device diagram

• Triac Regulator

A drill in the household today is simply irreplaceable; almost all craftsmen have it in their arsenal. Some models include an impact mechanism, which is shown by the diagram, which can be seen in fig. 1. In this case, the device is more functional. The device can be seen from the diagram in Fig. 2, on it, under the number 1, the speed controller is shown; under the number 2 - reverse; the number 3 indicates the brush holder with the brush itself; 4 is the motor stator; 5 - impeller designed to cool the engine; under the number 6 is the gearbox.

Schematic diagram of an electric drill.

Tool motor device

The drill has a collector electric motor in its design, which includes 3 main components, among them:

Figure 1. Scheme of the device of the percussion mechanism of the drill.

The first mentioned element is based on electrical steel, which has the quality of excellent magnetic permeability. It is made according to the principle of a cylinder and has devices for mounting stator windings. The latter are contained there in the amount of two, and their location is opposite each other. The stator is firmly fixed in the body of the main apparatus.

The rotor is represented by a shaft, on the latter a core is installed, made on the basis of the same steel. Along the latter there are grooves removed by an equal step. The windings are laid with a single wire and have taps that are designed to be fixed to the collector plates. This forms an anchor that has segments in its composition. The collector is located on the shaft shank and securely fixed to it. The rotor during the start-up rotates in the internal space of the stator on bearings. Brushes move along the plates during the operation of the installation. They are based on graphite.

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Triac Regulator

The triac controller located in the start button is responsible for the rotation of the unit when the drill is turned on. This regulator is mounted in the button housing and is located on a lining made of textolite. The board is designed in such a way that it has small dimensions, which allows it to be completely located in the trigger space. After the power button is activated, an immediate break occurs in the regulator of the apparatus, at this moment the circuit is closed in a meager period of time. And the regulator is not able to influence the voltage variation, however, it is subject to a change in the rms voltage level.

After the start of the drill, an alternating voltage enters the network.

Figure 2. Drill parts.

In parallel with this, a sinusoidal voltage is supplied to the control electrode of the triac. During the period when its level is greater than the operating voltage of the triac, the latter opens, which indicates the circuit is closed, at this moment the current flows through the load.

The wiring diagram and the connection of the installation button in different models from different manufacturing plants may differ. The most simplified of all the diagrams, and the one that best shows the principle of operation, is shown in Fig. 3. One wire from the power cord is connected to the speed controller. The figure shown shows circuit diagram apparatus, where "reg. rev." - speed controller, "1st st. exchange" - primary stator winding, "2nd stage of exchange." - respectively, secondary, "1st brush." - the first brush.

In order not to get confused, it should be remembered that the speed controller and the reverse control system are represented by completely different components of the tool, which in some models even have separate cases.

Figure 3. A typical diagram of a drill speed controller.

There are only 2 wires going to the speed controller. And the one that comes out of the speed controller is connected to the beginning of the stator primary. In the absence of a reverse, the end of the primary would be conjugated with the rotor brush, and the second brush would be conjugated with the beginning of the stator secondary. The end of the secondary goes to the second wire of the cord, from which the drill is powered during operation.

The rotor begins to work in the other direction at the moment when the end of the primary is connected to the second brush. In the reverse system, such a connection is carried out, for this reason the rotor brushes are mated with the stator windings through it. On fig. 4 shows the connection diagram of the reverse device. Wires in the amount of 4 pcs. go to the rotor brushes, those that are gray go to the end of the primary and the beginning of the secondary.

The system for adjusting the speed of the device assumes the presence of a capacitor and the connection to the regulator of wires that come from the outlet. If we take into account the installation from the example, then only two contacts are used, which are located below. The system is completely devoid of a capacitor, and the second wire of the cord is connected directly to the stator winding.

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Features of the apparatus reducer

Figure 4. Connection diagram for a drill button with reverse.

The drill has a gearbox in its design, which is responsible for reducing the number of revolutions of the working drill and increasing the torque. Many models have a gear reducer, which involves one gear. You can purchase hammers that provide for a certain number of gears, there may be two, while the system is like a gearbox, which is equipped with a conventional vehicle - a car.

The connection diagram of a number of installations existing on the modern market has shock functionality. Then the master with the presence of such a tool gets the opportunity to equip holes in the body of a concrete monolith. In such devices, a wavy element is mounted in the lateral region of the large gear, the same washer is located opposite.

The scheme, the connection of such an installation has some differences from the above models. Thus, in the process of work that involves the impact mode involved, the drill rests against the surface being machined, and the wavy components, interacting with a solid obstacle, begin to imitate impacts. These elements in the design after some time of operation of the installation need to be completely replaced.

The connection diagram of different models and manufacturers may differ from that presented in the example described above, however, the principle of operation of such a device remains the same.

Do-it-yourself electric drill repair

If you have certain skills, repairing a drill at home is quite simple. Of the numerous cases of drill breakdowns, several characteristic malfunctions can be distinguished, which are caused by improper operation of a power tool or defective elements from the manufacturer. These typical breakdowns include:

Failure of engine elements (stator, armature). - wear of brushes or their burning. - failure of the regulator and reverse switch. - Wear of bearings.

Poor quality clamp in the tool chuck.

The device of an electric drill (the simplest Chinese electric drill): 1 - speed controller, 2 - reverse, 3 - brush holder with a brush, 4 - motor stator, 5 - impeller for cooling the electric motor, 6 - gearbox.

The commutator electric motor of a drill contains three main elements - a stator, an armature and carbon brushes. The stator is made of electrical steel with high magnetic permeability. It has a cylindrical shape and grooves for laying stator windings. There are two stator windings and they are located opposite each other. The stator is rigidly fixed in the drill body.

Electric drill device: 1 - stator, 2 - stator winding (second winding under the rotor), 3 - rotor, 4 - rotor collector plates, 5 - brush holder with brush, 6 - reverse, 7 - speed controller.

The rotor is a shaft onto which a core of electrical steel is pressed. Grooves are machined along the entire length of the core, through an equal distance, for laying anchor windings. The windings are wound with a solid wire with taps for fastening to the collector plates. Thus, an anchor is formed, divided into segments. The collector is located on the shaft shank and is rigidly fixed on it. During operation, the rotor rotates inside the stator on bearings located at the beginning and end of the shaft.

Spring-loaded brushes move along the plates during operation. By the way, when a drill is being repaired, special attention should be paid to them. The brushes are pressed from graphite, they look like a parallelepiped with built-in flexible electrodes.

The most common type of breakdown is the wear of the motor brushes, which can be replaced independently at home. Sometimes, the brushes can be replaced without dismantling the drill body. For some models, it is enough to unscrew the plugs from the installation windows and install new brushes. For other models, replacement requires disassembly of the housing, in which case it is necessary to carefully remove the brush holders and remove the worn brushes from them.

Brushes are available at all normal power tool stores, and often an extra pair of brushes is included with a new power drill.

Do not wait until the brushes are worn down to the minimum size. This is fraught with the fact that the gap between the brush and the collector plates increases. As a result, increased sparking occurs, the collector plates become very hot and can “depart” from the base of the collector, which will lead to the need to replace the armature.

You can determine the need to replace the brushes by increased sparking, which is visible in the ventilation slots of the housing. The second way to determine this is the chaotic "twitching" of the drill during operation.

In second place, in terms of the number of drill breakdowns, you can put a malfunction of the engine elements and most often the anchor. The failure of the armature or stator occurs for two reasons - improper operation and poor-quality winding wire. World-famous manufacturers use expensive winding wire with double insulation with heat-resistant varnish, which significantly increases the reliability of engines. Accordingly, in cheap models, the quality of the winding wire insulation leaves much to be desired. Improper operation is reduced to frequent overloads of the drill or prolonged work, without interruptions to cool the engine. Do-it-yourself drill repair by rewinding the armature or stator, in this case it is impossible without special tools. Only a complete replacement of the element (exceptionally experienced repairmen will be able to rewind the armature or stator with their own hands).

To replace the rotor or stator, it is necessary to disassemble the housing, disconnect the wires, brushes, if necessary, remove the drive gear, and remove the entire motor along with the support bearings. Replace the defective element and reinstall the engine.

You can determine the malfunction of the armature by a characteristic smell, an increase in sparking, while the sparks have a circular motion in the direction of movement of the armature. Pronounced "burned" windings can be seen during visual inspection. But if the engine power has dropped, but there are no signs described above, then you should resort to the help of measuring instruments - an ohmmeter and a megohmmeter.

The windings (stator and armature) are subject to only three damages - an interturn electrical breakdown, a breakdown on the "housing" (magnetic circuit) and a winding break. The breakdown on the case is determined quite simply, it is enough to touch any output of the winding and the magnetic circuit with the probes of the megohmmeter. A resistance greater than 500 MΩ indicates no breakdown. It should be borne in mind that measurements should be carried out with a megohmmeter, in which the measuring voltage is not less than 100 volts. By making measurements with a simple multimeter, it is impossible to determine for sure that there is no breakdown, but you can determine that there is definitely a breakdown.

It is quite difficult to determine the interturn breakdown of the armature, unless, of course, it is visible visually. To do this, you can use a special transformer, which has only a primary winding and a gap in the magnetic circuit in the form of a gutter, to install an armature in it. In this case, the armature with its core becomes a secondary winding. Turning the armature so that the windings are alternately in operation, we apply a thin metal plate to the armature core. If the winding is short-circuited, then the plate begins to rattle strongly, while the winding heats up noticeably.

Often, an interturn short circuit is found in visible sections of the wire or armature busbar: the turns can be bent, crumpled (i.e., pressed against each other), or there can be any conductive particles between them. If so, it is necessary to eliminate these short circuits by repairing bruises in the tavern or removing foreign bodies, respectively. Also, a short can be detected between adjacent collector plates.

You can determine the breakage of the armature winding if you connect a milliammeter to adjacent armature plates and gradually turn the armature. In whole windings, a certain identical current will occur, a break will show either an increase in current or its complete absence.

A break in the stator windings is determined by connecting an ohmmeter to the disconnected ends of the windings, the absence of resistance indicates a complete break.

The speed of the drill is controlled by a triac controller located in the power button. It should be noted a simple adjustment scheme and a small number of parts. This regulator is assembled in a button case on a textolite substrate using microfilm technology. The board itself has a miniature size, which made it possible to place it in the trigger housing. The key point is that in the drill controller (in the triac) the circuit breaks and closes in milliseconds. And the regulator does not change the voltage that comes from the outlet in any way (however, the root-mean-square value of the voltage, which is shown by all voltmeters that measure alternating voltage, changes). More precisely, there is a pulse-phase control. If the button is pressed lightly, then the time when the circuit is closed is the smallest. As you press, the time the circuit is closed increases. When the button is pressed to the limit, the time when the circuit is closed is maximum or the circuit is not opened at all.

More scientifically, it looks like this. The principle of operation of the regulator is based on changing the moment (phase) of switching on the triac (closing the circuit) relative to the transition of the mains voltage through zero (the beginning of a positive or negative half-wave of the supply voltage).

Voltage diagrams: in the network (at the input of the regulator), at the control electrode of the triac, at the load (at the output of the regulator).

To make it easier to understand the operation of the regulator, we will build three time voltage diagrams: network voltage, on the control electrode of the triac and on the load. After the drill is connected to the network, an alternating voltage is supplied to the input of the regulator (upper diagram). At the same time, a sinusoidal voltage is applied to the control electrode of the triac (middle diagram). At the moment when its value exceeds the triac turn-on voltage, the triac will open (the circuit will close) and the mains current will flow through the load. After the value of the control voltage falls below the threshold, the triac remains open due to the fact that the load current exceeds the holding current. At the moment when the voltage at the input of the regulator changes its polarity, the triac closes. Then the process is repeated. Thus, the voltage across the load will have the shape of the diagram below.

The greater the amplitude of the control voltage, the earlier the triac will turn on, and therefore, the duration of the current pulse in the load will be longer. Conversely, the smaller the amplitude of the control signal, the shorter will be the duration of this pulse. The amplitude of the control voltage is controlled by a variable resistor connected to the drill trigger. It can be seen from the diagram that if the control voltage is not phase shifted, the control range will be from 50 to 100%. Therefore, in order to expand the range, the control voltage is shifted in phase, and then during the processes of pressing the trigger, the voltage at the output of the regulator will change as shown in the figure below.

It is shown how the voltage at the output of the regulator will change if you press the trigger of the drill.

Regulator repair.

The presence of voltage at the input terminals of the power button and the absence of voltage at the output indicates a malfunction of the contacts or components of the speed controller circuit. To disassemble the button, you can carefully pick up the latches of the protective cover and pull it off the button body. Visual inspection of the terminals will allow you to judge their performance. Blackened terminals are cleaned of soot with alcohol or fine sandpaper. Then the button is assembled again and checked for contact, if nothing has changed, then the button with the regulator must be replaced. The speed controller is made on a substrate and is completely filled with an insulating compound, therefore it cannot be repaired. Another characteristic malfunction of the button is the erasing of the working layer under the rheostat slider. The easiest way out is to replace the entire button.

Do-it-yourself drill button repair is possible only if you have certain skills. It is important to understand that after opening the case, many switching parts will simply fall out of the case. This can be prevented only by gently lifting the cover initially and by the desired sketching of the location of the contacts and springs.

The reverse device (if it is not located in the button housing) has its own changeover contacts, therefore it is also subject to contact loss. The disassembly and cleaning mechanism is the same as the buttons.

When buying a new speed controller, you should make sure that it is rated for the power of the drill, so if the power of the drill is 750W, the controller must be rated for a current of more than 3.4A (750W/220V=3.4A).

The wire connection diagram, and in particular the drill button connection diagram, may differ in different models. The simplest circuit, and best of all demonstrating the principle of operation, is as follows. One lead from the power cord is connected to the speed controller.

Electrical diagram of the drill. "reg. rev." - electric drill speed controller, "1st stage of exchange." - the first stator winding, "2nd stage of exchange." - the second stator winding, "1st brush." - first brush, "2nd brush." - the second brush.

In order not to be confused, it is important to understand that the speed controller and the reverse control device are two different parts that often have different housings.

The speed controller and reverse are in separate housings. The photo shows that only two wires are connected to the speed controller.

The only wire coming out of the speed controller is connected to the beginning of the first stator winding. If there were no reverse device, the end of the first winding would be connected to one of the rotor brushes, and the second rotor brush would be connected to the beginning of the second stator winding. The end of the second stator winding leads to the second wire of the power cord. That's the whole scheme.

A change in the direction of rotation of the rotor occurs when the end of the first stator winding is connected not to the first, but to the second brush, while the first brush is connected to the beginning of the second stator winding.

In the reverse device, such switching occurs, therefore the rotor brushes are connected to the stator windings through it. There may be a diagram on this device showing which wires are connected internally.

The scheme on the reverse of the electric drill (in the photo, the reverse is disconnected from the speed controller).

Wiring diagram for reverse electric drill.

Black wires lead to the rotor brushes (let the 5th contact be the first brush, and let the 6th contact be the second brush), gray wires - to the end of the first stator winding (let it be the 4th contact) and the beginning of the second (let it be 7- th contact). With the switch position shown in the photo, the end of the first stator winding with the first rotor brush (4th with 5th), and the beginning of the second stator winding with the second rotor brush (7th with 6th) are closed. When switching the reverse to the second position, the 4th is connected to the 6th, and the 7th to the 5th.

The design of the electric drill speed controller provides for the connection of a capacitor and the connection to the controller of both wires coming from the outlet. The diagram in the figure below, for a better understanding, is slightly simplified: there is no reverse device, the stator windings are not yet shown, to which the wires from the regulator are connected (see diagrams above).

Connection diagram of the button (speed controller) of the drill.

In the case of the described electric drill, only two lower contacts are used: the extreme left and the extreme right. There is no capacitor, and the second wire of the power cord is connected directly to the stator winding.

Connecting an electric drill button.

The drill reducer is designed to reduce the speed of the drill and increase the torque. The most common gear reducer with one gear. There are also drills with several gears, for example two, while the mechanism itself is somewhat reminiscent of a car gearbox.

The presence of extraneous sounds, rattle and wedging of the cartridge indicates a malfunction of the gearbox or gear shift mechanism, if any. In this case, it is necessary to inspect all gears and bearings. If worn splines or broken teeth on the gears are found, then a complete replacement of these elements is necessary.

Bearings are checked for suitability after removing them from the armature axis or drill body using special pullers. Clamping the inner clip with two fingers, you need to scroll the outer clip. Uneven jumping of the cage or “rustling”9, when scrolling, indicates the need to replace the bearing. An incorrectly replaced bearing will lead to anchor jamming, or, at best, the bearing will simply rotate in the seat.

Percussion action of a drill.

Some drills have an impact mode for chiseling holes in concrete walls. To do this, a wavy “washer”9 is placed on the side of the large gear, and the same “washer9” is opposite.

Large cog with undulations on the side.

When drilling with the impact mode turned on, when the drill rests against, for example, a concrete wall, the wavy washers9 touch and, due to their undulation, imitate impacts. “Washers9 wear out over time, and I need to replace them.

The wavy surfaces do not touch due to the spring.

Contiguous wavy surfaces. The spring is stretched.

Drill chuck replacement.

The chuck is subject to wear, namely the clamping jaws9, due to the ingress of dirt and abrasive residues of building materials into it. If the chuck is to be replaced, unscrew the fixing screw inside the chuck (left-hand thread) and unscrew it from the shaft.

The cord is checked with an ohmmeter, one probe is connected to the contact of the power plug, the other to the core of the cord. The absence of resistance indicates a break. In this case, the repair of the drill comes down to replacing the mains wire.

In conclusion, I would like to add: when assembling the drill after its repair, make sure that the wires are not pinched by the top cover. If everything is in order, the two halves will collapse without a gap. Otherwise, when tightening the screws, the wires may flatten or bite.

Attention, only TODAY!

sovetskyfilm.ru

Do-it-yourself electric drill repair. - blog SamElektrik.ru

Electric drill, do-it-yourself repair

The second article of the summer competition. This time the author is known to regular readers of the blog. This is Alexey Sidorkin, who already participated in the first competition with an article about a homemade time relay.

So, the article by Alexei Sidorkin:

I think that every person in his life had more than one event or incident for which he could not find a suitable explanation in any way, remaining a secret for for a long time. This is what happened with my drill.

My son-in-law Dmitry got this Bosch PSB 500 RE drill in May 1998 to equip his newly acquired apartment. At that time, not everyone had such a prestigious tool (power 500 W, speed control, reverse rotation, the possibility of shock mode - a “perforator”) in the household. The purchase caused quiet envy - I had a simple Soviet drill without any "bells and whistles". My daughter gave the Bosch drill later after the tragic death of her son-in-law during an accident in 2002.

Of course, my use of the tool was not “every day from morning to evening”, the drill was used for household needs, as in most ordinary families, plus the summer season in the country.

Fig.1. General form drills BoschPSB 500 RE.

The drill worked properly, successfully fulfilling all its options and functions ... and suddenly, 5-6 years ago, the speed controller stopped “obeying” - at any position / setting of the wheel / handwheel of the regulator, when the trigger was pressed, the drill immediately gave full speed without any smoothness. The first thing that came to mind, why there are no low speeds, is that the speed control circuit of the drill “burned out”. But by that time, other tools appeared on the farm, including a screwdriver and another drill in the village, and the work of the Bosch drill in low-speed mode was not so relevant, the hands never reached the troubleshooting.

More recently, I had to carefully work with a drill, and its high speed turned out to be very inopportune, and there were no other tools with a cartridge at hand. There is a repair shop near the house. household appliances. They told me there that the speed controller (hereinafter referred to as RO) for the Bosch drill is only “on order”, wait at least 2 months, the cost of work is 500 rubles.

I decided to figure it out on my own, after all, a power equipment adjuster, albeit retired.

Himself an adjuster, but went to the workshop? If it is urgent, but for a couple of hundred (earlier it was called “for a bottle”), then there is no point in “uncovering your rifle”, others should also be allowed to live.

I opened the drill, disconnected the RO (two detachable knife-type electrical contacts, two “under the screw” and one screw for fastening the power wire - Fig. 2).

Rice. 2. Connecting the speed controller to the drill.

The drill speed controller is a separate unit. In Figure 3, two halves (cover and body) of an already opened RC are almost life-size, the material is plastic, the halves are fixed “on latches” between themselves.

Rice. 3. Speed ​​​​regulator of the drill with the cover removed

Figure 3 shows: 1 - contact group; 2 - sliding contacts; 3 - resistor strips; 4 - handwheel of the adjusting screw; 5 - reciprocating trigger spring.

In the case of the speed controller for the drill, there is a contact group 1 and sliding contacts 2 in the form of two spring plates, driven by pressing the trigger and returning to their original position under the influence of the reciprocating-squeezing spring 5.

In the cover there is a capacitor (bottom) and a board (top) with electronic elements and two resistor strips 3, along which, when the trigger is pressed, contacts 2 slide to smoothly change the speed of the tool. The resistor strips are lubricated to protect the strips, reduce friction and prevent sparking of the sliding contacts.

An adjusting screw with a handwheel 4 on the trigger limits the depth of the trigger and the distance / length of sliding of the contacts 2 along the resistor strips 3, thereby determining the adjustment range and the maximum speed of the drill. If the adjusting screw is completely unscrewed, then the trigger, when fully pressed, closes the contact group to directly turn on the drill engine, bypassing the electronic adjusting elements, and the engine runs at the maximum possible speed (3000 rpm).

The drill speed controller circuit is almost identical to the rotary dimmer circuit. The differences are only in design and dimensions.

The scope of my work included checking the clarity of the trigger when pressed, the interaction of parts of the contact group, rotating the adjusting screw, leveling the distribution of lubricant on the resistor strips, cleaning accessible places from accumulated dust and dirt. No malfunctions, malfunctions or suspicious moments were found. In other words, I carried out a small revision, after which I assembled the drill, turned it on and ... the speed controller started working, as if nothing had happened!

Thus, the repair of the Bosch drill speed controller was reduced to a banal cleaning!

Many assumptions could be made regarding the causes of the temporary illness of the drill - from a blow or an unnoticed fall of the tool to malfunctions in the electronics. However, the analysis of the situation still tends to disrupt the operation of the “sliding contacts - resistor strips” pair for an unknown reason, it is enough that a speck (particle) just gets under one of the sliding contacts - and that’s it, there will be no adjustment. This is also evidenced by the inclusion of the tool immediately at full speed, which is possible only when the contact group is triggered.

Maybe this will be interesting too?

But, whatever you say, it turns out that the tool turned out to be an electrician himself and repaired himself!

Question from a reader

A reader, Alexander, contacted me by mail with the following request:

Good evening. I came across your blog where you repair a Bosch drill. I have a similar problem, only I have almost nothing to do with electronics. Foolishly, I dismantled the trigger of a bosch gsb 1600 RE drill. Everything worked fine before, somehow assembled, now the soft start does not work. Maybe in the wrong order and put the parts in the wrong place. I am attaching a photo of the disassembled. I hope it helps, the drill is good.

Photo of the disassembled Bosch drill button:

Bosch drill repair. The disassembled trigger is a button with a speed controller.

Bosch drill repair. Disassembled trigger - button

I don't know how to help the reader. Maybe someone will share their experience?

If you liked the article, vote for it here and now:

• 1. Marchenko Boris Danilovich with articles on welding cores and searching for hidden wiring (49%, 29 Votes)
• 3. Sergey Pikalov with an article about wiring in the construction version (34%, 20 Votes)
• 2. Alexey Sidorkin with an article about Bosch drill repair (17%, 10 Votes)

How to make a reverse for a power tool

One of the main tools of a do-it-yourselfer is an electric drill, and the speed of work and quality depend on its design and convenience. I have a Soviet-made electric drill, which has served faithfully for many years. The metal case of the gearbox and the bearings in the gearbox made it almost unkillable! My friends, who use modern foreign-made drills, have already changed several pieces during this time.

But! She has a small drawback: she does not have a reverse, which is very necessary for some jobs, especially when threading with machine taps. A few years ago, I decided to rid it of this shortcoming and I managed to solve this problem much better than it is implemented in factory-made drills in which the reverse switch is located above the start button.

I installed a button to switch to reverse mode on the back of the electric drill. If you compare it with a pistol, then it is located approximately in the area of ​​\u200b\u200bthe trigger. This button is a dual micro-switch with changeover contacts. The switch has high reliability, small dimensions and long term services. Such devices had two versions, in the form of a button and in the form of a toggle switch with switching contacts, and were installed in military equipment, as well as in professional industrial measuring equipment.

Why did I put a button and not a toggle switch? Because it seemed to me that it would be much more convenient to work this way, because you have to turn on the reverse mode for a short time and press the soft button thumb much easier than pulling the switch lever. Subsequently, this option fully justified itself. But you can also put a toggle switch - a matter of taste.

Motor reverse circuit

To reverse the collector motor, it is necessary to mechanically swap the ends of the stator winding of the motor; this requires a switch with two groups of switching contacts. When the reverse button is pressed, the brushes are connected to opposite stator windings. Naturally, the reverse button must be pressed only after the engine has completely stopped, otherwise you will break the gearbox.

Let's move on to reconstruction.

Having disassembled the drill, I determined the place for installing the button and cut a hole in the case for installing the button with a round file, soldered wires of the required length to the contacts of the button and proceeded to re-switch the connections. The fact is that a trigger is installed in the drill with thyristor regulator speed and when upgrading, this must be taken into account.

Thus, almost any power tool can be converted to reverse. Well, that's all - the drill is assembled and works great!

radioskot.ru

In order to repair a drill, you need to know its design features well. It should be noted that the design of the drill is quite simple. At the same time, various models have approximately the same layout, differing only in some individual details and workmanship.

The principle of operation of these devices is also quite universal, so you can quickly detect a problem and fix it without leaving your home.

In any electric drill, there is a case where the mechanical and electronic parts of the device and a chuck located on the main shaft of the drill are located. A drill is attached to the chuck, which is the working tool.

The main details of the electronic part:

• two-phase electric motor consisting of a rotor and a stator;
• start button, which is a switch;
• contact brushes located on the brush holder;
• reverse device;

• engine speed controller;
• start capacitor;
• cord or cable that provides power.

The mechanical component of the device consists of a bearing system and a gearbox. Due to the gearbox, the rotation of the electric motor is transmitted to the shaft at a reduced speed. If we are dealing with an impact drill or hammer drill, then here the gearbox provides both rotational and impact movement of the drill. To do this, in addition to gears, the design of the gearbox includes a ram, pistons and a striker.

Basic problems

Despite the high-quality assembly and reliable components, any drill can break. The most common problems are:

• breakdown of the electric motor, in particular, failure of the armature or stator;
• wear or burning of brushes;
• problems with thrust bearings;
• malfunction of the button that regulates speed;

• oxidation or combustion of the contacts of the start button;
• other problems, in particular breakage of the chuck.

As a rule, do-it-yourself drill repair does not involve repairing a broken part. This is not possible without special equipment. Often it is only necessary to find a problem and replace the broken part with a new one.

Malfunctions in the electrical part

Most often, the malfunction is that for some reason the motor does not turn on. In particular, if the cartridge can be easily turned, and the motor does not work, then we are dealing with a malfunction in the electrical part. This is also indicated by problems with speed control or reverse rotation.

If the malfunctions of the device are temporary, then this also indirectly indicates problems with the electrical component. Most often, contact brushes fail in this part. For example, if they are worn out by 40%, then this already leads to malfunctions. With more pronounced wear, the drill does not turn on at all.

To determine a malfunction in the electrical part, you need to determine the integrity of the cord with a tester, and then check the start button and start capacitor. Next, inspect the contact buttons and the integrity of the motor winding.

Mechanical problems

The main symptom of a problem in this part is considered to be the difficulty of the shaft, for example, if the cartridge does not scroll, but you hear the engine running. In this case (most often) we are dealing with the failure of bearings or a gearbox.

Thrust bearings break most often. It is possible to suspect the failure of the gearbox if the cartridge turns easily when the engine is running, but the rotation does not go to the main shaft.

In addition, among the mechanical malfunctions, there is a temporary stoppage of the drill, excessive noise during the operation of the device, a buzz or insufficient shaft speed.

When working with a rotary hammer, there may be a failure in the impact device system.

The failure of the mechanical reverse switch depends on its design. Very often, the finger that moves the additional gear falls out or breaks.

Some of the problems may relate to the drill chuck. This can manifest itself in the difficulty of removing and fixing the drill. In some cases, the chuck may rotate relative to the drill shaft.

To eliminate the above malfunctions, partial or complete disassembly of the drill is necessary.

Separate common malfunctions and their do-it-yourself repair

Many breakdowns of power tools can be repaired on their own. This will take a little time to repair the drill, but will save you some money.

• Replacing worn contact brushes

This failure is one of the most common, as the brushes on many models wear out quite quickly. You can suspect a problem when sparks appear in the area where the brushes are in contact with the armature. In addition, if these parts fail, the drill may malfunction during an increase in load.

For most devices, getting access to the brushes is quite simple (you need to unscrew the special screws or caps that cover these parts), so replacing them is a fairly simple event. However, in some models, this requires disassembling the body and pulling out the brush holder.

In any case, to eliminate the malfunction, it is necessary to replace worn parts with new ones. They should be carefully fixed on the brush holder, while tightening the electrical contact of the wire. When replacing, it is necessary to ensure that the contact between the brush and the collector is sufficiently reliable.

• Failure of the electric motor

Motor failures are considered the second most common failure. Most often, the armature or stator winding is damaged. Such breakdowns can occur both in the presence of factory defects, and in case of improper work with a drill.

In particular, these parts fail during long continuous operation and increased load when the drill is jammed. You can detect such a problem either by the smell of burning, or simply visually.

If the fault is not detected in this way, then it is necessary to check the winding with an ohmmeter, tester or megohmmeter. The most common problems are short circuit between turns, broken wire or turn.

It is impossible to repair the anchor or stator on your own. Therefore, in case of failure, these parts must be replaced.

To replace these components, disassemble the body of the device, disconnect the brushes and wires, and then pull out the motor itself.

Problems with electrical components

Video about replacing a button in a drill

During the operation of the drill, the start button and the shaft speed controller can often fail. In this case, the drill button may need to be repaired. Here, first of all, the presence of voltage at the output and input terminals of the button is checked. In case you did not find a signal, you need to check the integrity of the wires leading to it. If they are in order, then it is necessary to remove its case and check the button contacts.

It is enough to do this visually, since you can see sticking or burning of contacts without any problems. In any case, you need to clean them with a special sandpaper and wipe with an alcohol solution. After all these procedures, the voltage is checked again. If this helps, put the cover of the button housing back in place. The tool is collected. If this does not help, you need to replace the old button with a new one.

Quite often, a situation arises when the electric motor does not start with the button, but it is serviceable. This may be due to a faulty start capacitor. You can check its serviceability visually, since when it fails, it quickly changes color.

The electronic mechanism for reversing rotation is based on the closing / opening of contacts. Repair and maintenance of this system is carried out with a tester or an ohmmeter. All reverse wires going to the electric motor (brushes, stator) are checked.

Thus, the drill can break at the most unfortunate moment. To understand how to quickly troubleshoot and repair a drill, you need to know its design and signs of certain problems.

All modern drills are produced with built-in engine speed controllers, but for sure, in the arsenal of every radio amateur there is an old Soviet drill, in which the change in speed was not conceived, which drastically reduces performance.

The figure below shows a diagram of a speed controller for a drill motor, assembled as a separate external unit and suitable for any drills up to 1.8 kW, as well as for other similar devices that use an AC commutator motor, for example, grinders. The details of the regulator in the diagram are selected for a typical drill with a power of about 270 W, 650 rpm, voltage 220V.

Thyristor type KU202N for the purpose of its normal cooling is mounted on a radiator. To set the desired speed of the electric motor, the regulator cord is connected to a 220 V mains socket, and the drill is already plugged into it. Then, by moving the variable resistance knob R, set the required speed for the old drill.

When working with a drill, it is periodically necessary to smoothly change its speed, but a simple decrease in the supply voltage leads to both a decrease in speed and a loss of power, the circuit proposed below is devoid of this drawback, since it uses regulation with feedback according to the current of the electric motor, as a result, with an increase in load, the torque on the EM shaft increases.

The circuit uses capacitors with an operating voltage of at least 400 V, all resistances with a power of at least 1 W.

The presented scheme is simple enough to be repeated even by a novice radio amateur. The components and parts required for assembly are cheap and readily available. It is recommended to assemble the structure in a separate box with a socket. Such a device can be used as a carrier with a typical power regulator

The principle of operation of this amateur radio homemade product is as follows, when the load is small, the current flows small, and as soon as the load increases, the speed increases smoothly.

The LM317 micro assembly needs to be installed on the heatsink. Diodes 1N4007 can be replaced with similar ones designed for a current of at least 1A. The printed circuit board is made on one-sided fiberglass. Resistance R5 with a power of at least 2W, or wire.

The 12V power supply should have a small current margin. Resistor R1 sets the required idle speed. The resistance R2 is necessary to set the sensitivity in relation to the load, it sets the required moment for increasing the number of revolutions of the microdrill. If you increase the capacitance of C4, then the high speed delay time increases.

The circuit shown below makes it possible to assemble a very simple, cheap and useful speed controller for a 12-volt micro drill for drilling holes in printed circuit boards in amateur radio practice.

The LM555 microassembly is used as a pulse-width modulator. The supply voltage for PWM is reduced and stabilized using the LM7805 chip). Precision trimmer P1 50 KΩ allows you to adjust the speed of rotation of the drill. Field-effect transistor IRL530N is used as an output drive element and can switch current up to 27A. In addition, it has a fast switching time and low resistance. Diode 1N4007 is needed to protect against counter EMF. Alternatively, you can take the MBR1645 Schottky diode.

Today it is impossible to find a person who would not know about the existence of an electric drill. Many have used this tool. But not everyone knows how this irreplaceable thing in the household works.

Inside the body of the drill there is an electric motor, its cooling system, a gearbox, a drill speed controller. It is worth talking a little more about the operation of the drill speed controller. All parts wear out during operation, the drill power button is especially susceptible to this process. And it is directly connected to the speed control system.

The purpose of the speed controller

The speed controller of a modern electric drill is located inside the power button of the device. To achieve such a small size allows microfilm technology, by which it is assembled. All parts and the board itself, on which these parts are located, are small in size. The main part of the regulator is a triac. The principle of its operation is to change the moment of closing the circuit and turning on the triac. It happens like this:

1. After turning on the button, the triac receives a voltage that has a sinusoidal shape on its control electrode.
2. The triac opens and current begins to flow through the load.

With a larger amplitude of the control voltage, the triac turns on earlier. The amplitude is controlled by a variable resistor, which is connected to the trigger of the drill. The connection diagram of the button in different models may be slightly different. Just do not confuse the speed controller with the reverse control device. These are completely different things. Sometimes they can be placed in different buildings. The speed controller may provide for the connection of a capacitor and both wires from the outlet.

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Using a drill as a machine

Figure 1. A typical diagram of a drill speed controller.

A hand drill can be used non-standard. On its basis, a variety of machines are made: drilling, grinding, circular and others. In such machines, the speed control function is very important. For most household drills, the speed is controlled by the start button of the device. The more it is pressed, the higher the speed. But they are fixed only at the maximum values. This can be a significant disadvantage in most cases.

You can get out of this situation by independently manufacturing a remote version of the speed controller. As a regulator, it is quite possible to use a dimmer, which is usually used to adjust the illumination. The controller circuit is quite simple and is shown in Fig. 1. To make it, you need to attach wires of different lengths to the outlet. The long wire is connected to the plug at the other end. The rest is going according to the scheme. It is recommended to use an additional circuit breaker that will turn off the device in case of an accident.

Homemade speed controller is ready. You can do a test run. If it works fine, you can put it in a suitable size box and fix it on the bed of the future machine in a convenient place.

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Repair of a button with a speed controller

Figure 2. Scheme of the speed controller for a microdrill.

Button repair is a rather difficult process that requires certain skills. When opening the case, some parts may simply fall out and be lost. Therefore, caution is needed in the work. In the event of a malfunction, the triac usually fails. This item is very cheap. Disassembly and repair take place in the following order:

1. Disassemble the button housing.
2. Rinse and clean the insides.
3. Remove the board with the circuit on it.
4. Solder the burnt part.
5. Solder new part.

Disassembling the case is very easy. It is necessary to bend the sidewalls and remove the cover from the latches. Everything must be done carefully and carefully so as not to lose 2 springs that can pop out. It is recommended to clean and wipe the insides with alcohol. Clamps-contacts in the form of copper squares slide out of the grooves, the board can be easily removed. A burnt triac is usually clearly visible. It remains to unsolder it and solder a new part in its place. The regulator is assembled in the reverse order.