How to put a speed controller on an angle grinder

How to reduce the speed on the angle grinder with your own hands?

Collector motors with series excitation are used in lathes with speed control. They can operate on direct or alternating current. This type of motor is easily regulated by changing the current in the circuit.

Because modern controllers use key-pulse control, they tend to heat up very little and can be built into even small tools. To control the speed a potentiometer with a knob on the handle of the machine is used.

Why control the speed of the blade?

Different cutting or grinding speeds are required by the physical properties of the material being worked on. For example, high speed at low pressure is required when cutting hard materials that might otherwise crumble or splinter. Soft materials not resistant to heat (thermoplastics, wood), on the contrary, require low speed:

• ceramics: 10000 rpm;
• metal: 8000 rpm;
• rigid plastics: 5000. 8000 rpm;
• wood: 3000 to 5000 rpm;
• Soft plastics: less than 2000 rpm.

All professional tools are equipped with a stabilized speed regulator, but inexpensive household angle grinder, power less than 1200 watts, are not always complemented by it. In this article we will talk about how to make such a regulator yourself to reduce the speed.

RPM regulator for angle grinder with their own hands

Although the creation of a regulator for the RPM angle grinder few, who is necessary, there are still models that have made manual adjustment of disk speed. The regulation of the angle grinder is much different from the electric electric screwdriver or drill, because:

• A completely different grip is used throughout the operation.
• It is forbidden to make adjustments during work. Regulation must only be carried out when the machine is switched off.

The disc speed must be adjusted

• When cutting metal (regardless of the thickness of the material) the result of the work carried out depends on the speed of the disc. If you are cutting metal of great thickness, the speed should be as high as possible. If you are working with a material that is not very thick, then the speed must be reduced, as high speeds quickly wash out the disc surface.
• There is a definite risk if you are cutting tiles at high speed. Also, the disk, spinning at high speed, begins to beat off small pieces of material, thereby making its surface scratchy. Since the stone has a variety of types, a specific speed is used for each type. High speeds are used for many minerals.
• If sanding or polishing is performed, then the adjustment of the speed of the angle grinder is simply necessary. If the rotational speed is not set correctly, the surface of the material will be damaged. For example, material that has a paint coating can be spoiled.
• If you constantly use discs that have different diameters, then the speed controller for the angle grinder must be available. If you change the angle grinder disc for another disc that has a larger diameter, the RPM should be reduced. You can not hold a grinder in your hands, which has a disc with a huge diameter.
• The choice of speed of rotation when polishing concrete material is dependent on the use of a particular type of crown. The torque must not be reduced if the speed is reduced.
• If you are using a diamond disc, the speed must be reduced, otherwise the surface will start to fail due to overheating. Of course, if you’re using an angle grinder to cut pipes, angles, or profiles, then having a regulator is unnecessary. But if the angle grinder is used for a variety of purposes, then a speed controller for the angle grinder is just necessary. All of these reasons show that the presence of a regulator of angle grinder is a must.

Description of angle grinder controller

The angle grinder regulator is a rheostat (variable resistor) that reduces the voltage (everything is done by the regulator). It is necessary to control the amount of current, because if the number of revolutions is reduced, the power of the construction machine will decrease. Consequently, there will be a decrease in torque. As a result, it will become a small value of voltage, and at a certain resistance the electric motor will not be able to turn the shaft. Therefore, it is necessary to follow a certain circuit: The scheme of the angle grinder is made up of a soft starter module and directly the speed regulator.

Modern advanced models have a distinctive electronic system, and not everyone can afford to buy it.

Independent creation of the regulator

How to make a regulator by yourself? The attempt to fit an ordinary electronic device designed to change the electric power (dimmer) ends up with nothing. First of all, the dimmer for the angle grinder is designed for a different load. Also the dimmer has no overlap with the control of the electric motor winding. Therefore, it is necessary to install a separate circuit. You also need to think about where it will be located inside the body of the angle grinder.

An important point: if you do not have any experience in working with electrical circuits, it is best to buy a ready-made regulator for angle grinder or angle grinder with the presence of this function.

A simple semiconductor device (thyristor regulator) can be constructed with your own hands. For this procedure will need 5 radio elements. Radio elements can be bought at the market. Thanks to the compactness you can easily hold the prepared circuit in the angle grinder, without damaging the ergonomics and reliability. However, preservation of torque does not occur when reducing the RPM on the angle grinder. This option is best suited for processing soft metals, as well as tin, which has a small thickness.

If you are processing stone, you need to install a disk that has the size of 180 millimeters. Next, you need to create a more complicated regulator circuit. In this circuit, the control module will be a chip KR1182PM1. This circuit has a control over the current at different speeds, and also makes the loss of torque to a minimum when reducing the speed. With this circuit, the operation of the engine is increased.

If the angle grinder is used as a circular grinder, it is necessary to equip the angle grinder with a connection point. Due to this point, the connection is made and the RPMs can be remotely regulated. You get a great homemade speed controller.

The way you have made the regulator does not depend on the fact that it is an indispensable component of an angle grinder, which makes the possibilities of work wider and allows the comfortable use of this construction tool. Also, after installing the regulator, it is necessary to conduct a test run of the angle grinder to check: whether the construction tool does not tear out of his hands. External speed controller for angle grinder with your own hands can be made.

What are the low speeds for on the angle grinder??

The integrated disc speed control enables gentle machining of materials such as plastics and wood. Comfort and safety at low speed increases. This function is especially useful in electrical and radio assembly practice, in car repair shops and restoration workshops.

In addition, there is a strong opinion among professional users of power tools that the easier the device is arranged, the more reliable it is. And it is better to put additional service “stuff” outside the power unit. In this case, the repair of equipment is greatly simplified. That’s why some companies specifically produce remote separate electronic regulators, which are connected to the mains cord of the machine.

Electrical configuration of the angle grinder

Over 40 years, the appearance of angle grinder has not changed: oblong body with built-in motor and gear box, screwed on the side handle and protective casing.

The angle grinder, as well as any tool, sooner or later refuses to work. But there are situations when the simplest repair of electrical equipment is sufficient to eliminate the malfunction. To perform this minor repair, you need to have an idea of how such equipment works inside, and be able to read its electrical scheme.

The electrical circuit of the grinder consists of these elements:

The simplest regulator scheme

Electrical diagram of the speed controller for angle grinder is gathered on the circuit board or mounted. The printed board, too, can be made by yourself with textolite and bleach. A mixture of hydrogen peroxide, salt and citric acid can be used instead of iron.

Diagram of motor speed regulator for angle grinder

Circuit Diagram Configuration

• resistor R1 (4.7 kOhm);
• DIAC symmetrical thyristor (DB3);
• symmetrical thyristor TRIAC (VT-136/138)
• trimmer resistor VR1 (500 kOhm);
• capacitor C1 (0,1µF400V).

Principle of operation

The circuit working principle is as follows. VR1 is responsible for the charging time of C1. When voltage is applied to the circuit, the thyristors are closed and the output is 0. As the capacitor is charged, the voltage in the capacitor increases and opens the DIAC, which gives the voltage to TRIAC. It also opens and allows current to flow. Then both thyristors are closed and stay in this position until the full reverse charge of C1. The output is a complex waveform with an amplitude that depends directly on the operating time of the circuit C1-VR1-R1.

Speed regulator wiring diagram

Final assembly and testing of the regulator

On a circuit board or a copper (aluminum) radiator is assembled circuit. When mounted assembly is especially important place of thyristors installation (strictly on the radiator, it plays the role of heat sink). Then there is a mandatory check of the functionality of the circuit with an ordinary light bulb. The smoothness of change of incandescence will be the same as in the finished speed controller for angle grinder after final assembly.

The factory models include a plastic adjustment wheel, if desired, you can also buy it separately and include it in the kit of the homemade regulator. If the test was successful, the regulator is mounted on the angle grinder and cut into the power circuit of the tool.

Smooth start of the angle grinder motor with your own hands

Everyone who uses the angle grinder more than one year, it breaks. At first, every master tried to repair the sparkling grinder himself, hoping that it will work after replacing the brushes. Usually, after such an attempt, the broken tool is left lying on the shelf with burned-out windings. And to replace it, you buy a new angle grinder.

Drills, screwdrivers, rotary grinders, milling machines are necessarily equipped with a speed regulator. Some so-called calibration grinders are also equipped with a regulator, and conventional angle grinders have only a button on.

Low-power angle grinders manufacturers do not deliberately complicate with additional circuits, because such power tools should cost cheap. It is clear, of course, that the life of an inexpensive tool is always shorter than that of a more expensive professional.

The simplest angle grinder can be upgraded so that its gearbox and armature winding wires are no longer damaged. These troubles predominantly occur with a sharp, in other words, a shock start of the angle grinder.

All you need to do is just assemble the electronic circuit and fix it in the box. In a separate box because there is very little space in the handle of the grinder.

A tested, working circuit is shown below. It was originally designed to regulate the incandescence of lamps, that is, to work on an active load. Its main advantage ? simplicity.

• The highlight of the soft starter whose circuit diagram you see is the K1182PM1R chip. This chip is highly specialized, domestically produced.
• The acceleration time can be increased by selecting a higher capacitor C3. While charging this capacitor, the electric motor reaches its maximum speed.
• It is not necessary to replace the resistor R1 with a variable resistor. The 68 kOhm resistor is optimal for this circuit. With this setting you can smoothly start the angle grinder with a power of 600 to 1500 watts.
• If you are going to build a power regulator, then you need to replace the resistor R1 with a variable resistance. Resistance of 100 kohm or more does not reduce the output voltage. By short-circuiting the microcircuit legs, you can turn off the connected angle grinder at all.
• Having inserted in a power circuit a triac VS1 type TC-122-25, that is on 25A, it is possible to smoothly start practically any available grinder, power from 600 to 2700 W. And there is a large power reserve in case the grinder jams. For connection of angle grinders with power up to 1500 W, imported semistors BT139, BT140 are enough. These less powerful electronic switches are cheaper.

The triac in the above circuit is not fully opened, it cuts off about 15V of line voltage. This voltage drop has no effect on the operation of the angle grinder. But when the semistors get hot, the speed of the connected tool decreases greatly. This problem is solved by installing a heat sink.

This simple circuit has one more disadvantage. it is not compatible with the RPM regulator installed in the tool.

The assembled circuit should be hidden in a plastic box. The case of insulating material is important, because you need to protect yourself from the mains voltage. You can buy a junction box at the electrical goods store.

A socket is screwed to the box and a cable and plug are connected, making this design look like an extension cord.

If experience allows and there is a desire, you can assemble a more complex circuit of soft starter. The wiring diagram below is standard for the XS-12 module. This module is factory installed in power tools.

If you need to change the speed of the connected electric motor, then the circuit is complicated: you need to install trimmer for 100 kOhm and adjusting resistor for 50 kOhm. Or you can simply and roughly implement a 470 kOhm variable between the 47 kOhm resistor and the diode.

It is desirable to connect a 1 Mohm resistor in parallel to the capacitor C2 (it is not shown in the schematic below).

The supply voltage of the LM358 ranges from 5V to 35V. Supply voltage is less than 25V. You can therefore do without the additional DZ.

Whatever softstarter circuit you have built, never run the tool connected to it under load. Any soft starter can be burned out if you are in a hurry. Wait for the angle grinder to spin up, then work.

Motor types

The motors are different in traits. This means that one or the other equipment is operated at different speeds of rotation of the shaft, which starts the mechanism. The motor can be:

Mainly three-phase motors are found in factories or large factories. At home criteria are used single-phase and two-phase. This electricity is enough to run your home appliances.

Working principles

Regulator of electric motor 220V without loss of power is used to support the initial speed of rotation of the shaft. This is one of the main principles of this device, which is called a frequency regulator.

With his help, the appliance operates at the set frequency of motor rotation and does not reduce it. Also the motor speed regulator affects the cooling and ventilation of the motor. The power is used to set the speed, which can be raised or lowered.

The question of how to reduce the speed of the electric motor 220V, many people have asked. But this procedure is quite straightforward. One has only to change the frequency of the supply voltage, which significantly reduces the performance of the motor shaft. It is also possible to change the power of the motor, engaging in all of this its coils. The control of electricity is tightly intertwined with the magnetic field and the slip of the motor. For such actions mainly use autotransformer, home regulators, which reduce the speed of this mechanism. But you should also keep in mind that it will reduce the power of the motor.

Rotation of the shaft

Asynchronous motor speed regulator is dependent on the current connection to the mechanism. The essence of the operation of an asynchronous motor depends on the magnetic coils through which the frame passes. It turns on the sliding contacts. And when it turns 180 degrees, the connection will flow in the opposite direction on these contacts. Thus, the rotation remains the same. But in all this action a suitable effect will not be obtained. It will take effect after putting a couple of 10 frames of this type into the mechanism.

Collector motor is used very often. Its operation is ordinary, because the current flows directly through, so that the motor does not lose power, and the mechanism consumes less electricity.

The washing machine motor also needs a power adjustment. To do this, special boards have been made, which are controlled by their own work: the board of speed control of the washing machine motor has a multi-functional use, because in its application the voltage is reduced, but the power of rotation is not lost.

The circuit of this board is tested. It is worth only to put a bridge of diodes, picking up the optocoupler for the LED. At the same time it is necessary to put the triac on the radiator. In the main the motor adjustment starts from 1000 rpm.

If you are not satisfied with the power regulator and its functionality is not enough, you can make or improve the mechanism. For this you need to take into account the current strength, which should not exceed 70A, and the heat loss when using. Therefore you can install an ammeter to adjust the circuit. The frequency will be small and will be determined by the capacitor C2.

Next is to adjust the regulator and its frequency. At the output this pulse will go through a push-pull amplifier on transistors. You can also make 2 resistors that will serve as an output for the cooling system of the computer. That the circuit does not burn out requires a special blocker, which will serve as a double current value. So this mechanism will work for a long time and in a suitable volume. Power controllers ensure long and cost-effective life for your electrical equipment.

Thyristor-based device

This model in Diagram 1 uses two thyristors in parallel, although they can be replaced by a triac.

Scheme 1. Thyristor speed control of collector motor without loss of power.

This circuit controls by opening or closing thyristors (triacs) with a phase-shift through the neutral. The following circuit modifications are used to correctly control a collector motor:

• Installation of LRC circuits consisting of capacitors, resistors and chokes.
• Adding capacitance to the input.
• thyristors or triacs, whose current exceeds the rated value of motor current in the range from 3.8 times.

This type of regulators has advantages and disadvantages. The first are low price, low weight and dimensions. The second should include the following:

• Use for motors of small capacity;
• Noise and jerking of the motor occurs;
• When using a triac circuit, the unvarying U voltage is delivered to the slider.

This type of regulator is used in fans, condensers, washing machines and electric drills. Performs its functions well, in spite of the drawbacks.

Design features

Asynchronous motor has no distinct poles, unlike a constant current motor. The number of poles is determined by the number of coils in the windings of the non-moving part (stator) and the method of connection. In asynchronous machine with 4 coils the magnetic flux passes. The stator is made of special steel sheets (electrical steel), reducing to zero eddy currents, in which there is considerable heating of the windings. It leads to massive inter-turn short circuits.

The tin or core of the rotor is pressed directly on the shaft. There is a small gap between the rotor and the stator. The rotor winding is made in the form of a “squirrel cage” and is made of copper or duralumin rods.

READ Cut-off saw of angle grinder with My Hands

In motors up to 100 kW the aluminum, which has low density, is used for casting into the slots of the rotor core. But despite such a device, the motors of this type heat up. To solve this problem we use forced cooling fans mounted on the shaft. These motors are ordinary and reliable. But motors consume a high current at start-up, 7 times the nominal current. Because of this, they have a small starting torque, because most of the electricity goes to heat the windings.

How to make the speed controller of angle grinder with my own hands

If you have an old angle grinder in your arsenal, do not rush to write it off. Using a simple circuit diagram, the device can be easily upgraded by adding to it the function to change the speed. Thanks to the simple regulator, which is real to assemble their own hands in a few hours, the functionality of the machine will increase significantly. By reducing the speed, the angle grinder can be used as a grinding and sharpening machine for different types of materials. There are new opportunities for the use of additional attachments and accessories.

If the angle grinder is not armed with a speed regulator, can it be set without the help of others? Most angle grinders (angle grinders), commonly known as rotary grinders, have a speed regulator.

The speed regulator is located on the body of the angle grinder

Consideration of the various adjustments should begin with an analysis of the electronic circuit of the angle grinder.

The simplest representation of the electrical circuit diagram of the grinder

The more advanced models automatically maintain the speed of rotation regardless of the load, but more common are tools with manual adjustment of disk speed. If the drill or electronic electric screwdriver used the trigger-type regulator, then on the angle grinder such a principle of regulation is not feasible. First. the features of the tool involves a different hand grip when working. B-2- the adjustment during operation is not allowed, because the speed value is set when the motor is off.

How to assemble the regulator with their own hands?

Simplified and fairly reliable in operation frequency converter for angle grinder is constructed by our own hands from available electrical parts. At the bottom there is a scheme, which shows all the required components for assembling the device we are interested in on the printed circuit board.

• DIAC (DB3) symmetric triode thyristor (or triac, simister);
• resistor (resistance) R1 (its parameters should be 4.7 kOhm);
• additional triac BT136/138 (TRIAC);
• the capacitor C1 (400 V, 0,1 μF);
• an additional resistance VR1 of 500 kOhm.

A similar circuit functions by the following method.

• The charging time of the capacitor is modified by an auxiliary resistor (it’s called a trimmer). When voltage is applied to the circuit, the triacs are in the gated position and zero voltage is observed on the pin.
• When the capacitor is being charged we see that the voltage across the capacitor rises and this leads to the opening of the DB3 triac. This causes the voltage to reach the VT136/138. This thyristor element also opens and an electric current flows through it.
• After that the symmetrical components are closed again and stay in a similar status until the absolute overcharge of the capacitor in the opposite direction.
• On the output we finally get a complexly configured deterministic finite energy signal. Its exact range is determined by the function period of the circuit capacitor. auxiliary resistance. resistance R1.

The triacs are usually mounted on a printed circuit board. It can easily be made of textolite (multi-layer compressed plastic consisting of insulating fibers and foil). Some masters cut out the board with a cutter. It is practiced to place circuit elements in the way of hinged mounting. The simulators are mounted only on aluminum or copper heat exchanger. It acts as a good heat sink.

You test the assembled device with an ordinary 40-60 watt incandescent lamp. You connect it to the circuit and adjust the lamp power. If the brightness changes, you have done everything correctly. Now you can mount the controller in the casing of the angle grinder. To implement this can be not very easy, because you need to ensure that the auxiliary device is not a hindrance to you when using the angle grinder.

The place of installation of the bush control device you will need to calculate yourself, according to the peculiarities of the design of the angle grinder. The installation of the circuit is done:

Speed regulator for angle grinder

• in an add-on box mounted on the body of the machine;
• into the handle of the holder;
• in a small empty niche (it is intended for cooling and air circulation) in the rear area of the angle grinder.

The circuit itself is connected to the device by integrating it into the electrical power supply channel of the angle grinder. You won’t have any trouble with this, I should think.

READ Patriot 125 angle grinder with RPM control

Why do the angle grinder soft start and speed regulator?

In modern angle grinders use 2 necessary options that increase the performance and safety of the equipment:

• speed regulator (frequency converter). a device designed to convert the speed of the motor in different modes of operation;
• soft starter. a scheme that provides a leisurely build-up of motor speeds from zero to the limit when the unit is connected.

Used in electromechanical equipment, the structure of which includes an alternating current electric motor with a collector. Contribute to reduction of wear of mechanical parts of the unit when switching on. Reduce the load on the machine’s electrical components by putting them into operation smoothly. As revealed by studies of the qualities of materials, especially the strongest wear of the contacting nodes are produced during the sudden transition from a stationary state to a fast activity. For example, one start-up of an internal combustion engine in a car equals the wear of a piston and a group of sealing rings by 700 kilometers of run.

When power supply is switched on the jumping state is made from standstill to wheel rotation with the swiftness of 2.5-10 thousand revolutions per 60 seconds. Anyone who has ever used an angle grinder knows very well the feeling that the tool just “flies out of his hands. It is at this moment that most of the accidents involving the machine occur.

The rotor and stator windings feel the same load. AC motor with a collector starts in the short circuit mode, the EMF is already pushing the shaft forward, but the force of inertia still does not allow it to spin. A surge of inrush current is generated in the motor coils. Even though by design they are designed for this kind of work, in time there comes a moment (for example, when there is a voltage drop in the mains) when the winding insulator can not stand and a short circuit occurs between the coils.

When introducing the instrument circuitry soft start device and change the frequency of rotation of the motor, all of the above troubles disappear spontaneously. Above all, the sudden and significant mains voltage drop during start-up of the tool is eliminated. It is clear from this that household appliances are not in danger of failure. And the circuit breakers on the electricity meter will not trip and cut off the current in the apartment or house.

The scheme of soft start is applied to angle grinders medium and high price segment, the knot of speed control. more and more in professional modifications of angle grinders. Speed control makes it possible to process angle grinder soft materials, to carry out delicate grinding and polishing, because at higher speeds wood or paint is simply burned. The auxiliary circuit increases the price of the tool, but it extends the service life and the degree of safety in use.

Why angle grinder soft start and speed regulator?

Modern angle grinders use 2 necessary options that increase the performance and safety of the equipment:

• Speed regulator (frequency converter) is a device designed to convert the speed of the motor in various operating modes;
• soft start device. a scheme that provides a leisurely build-up of motor rpm from zero to the limit value when the unit is connected.

They are used in electromechanical equipment, in the structure of which an AC electric motor with a collector is practiced. The following measures reduce wear and tear of the mechanical parts of the machine when it is switched on. Reduce the load on the electrical components of the machine, putting them into operation smoothly. Studies of the qualities of materials have shown that the strongest wear and tear of the contacting parts occurs during the sudden transition from a stationary state to a fast activity. For example, one start of an internal combustion engine in a car is equal to the wear of the piston and the group of sealing rings by 700 kilometers of run.

When the power is on, it makes a jump from stationary state to wheel rotation at a rate of 2.5-10 thousand revolutions in 60 seconds. Anyone who has used an angle grinder knows very well the feeling that the tool directly “flies out of his hands”. It is at this moment that most of the accidents involving the machine’s mechanical parts happen.

The rotor and stator windings feel the same load. The alternating current motor with the collector starts in the short circuit mode, the EMF is already pushing the shaft forward but the inertia force does not yet allow it to rotate. The inrush current in the motor coils is generated. Despite the fact that by design they are designed for such work, in time there comes a moment (for example, when there is a voltage drop in the electrical system), when the winding insulator is not able to withstand and a short circuit occurs between the coils.

When introducing the schemes of the soft starter and change of frequency of rotation of the motor into the wiring diagram of the tool kit, all the above described troubles disappear spontaneously. In addition, the problem of a sudden and significant voltage drop in the mains supply during the start-up of the tool is solved. From this it is clear that household appliances will not be in danger of failure. And the circuit breakers on the electric meter will not trip and turn off the current in the apartment or house.

The scheme of soft start is used in medium and high price segment angle grinders, the knot of speed control. more and more in professional modifications of angle grinders. Speed regulation allows you to process soft materials, to perform delicate grinding and polishing, because at higher speed wood or paint will simply burn off. Auxiliary circuitry raises the price of the tool, but it extends the life and degree of safety in use.

What is the function, principle of operation, circuit diagram, pluses angle grinder with a regulator

the angle grinder, not equipped with a speed control device, operates exclusively at maximum speed. Equipped with this option allows you to reduce the speed to a value that allows high-quality processing of materials that is not possible at maximum mode.

The electronic block of the speed regulator is based on a modified principle of dimmer, where the power is changed manually by changing the value of the variable resistor. Electronic control of the current on the spindle shaft maintains the torque, which ensures the performance of the angle grinder. The main working elements of such a scheme can be either a semiconductor device triac, or a more advanced version with an integrated circuit.

Wiring diagram without power regulator

The wiring diagram of conventional household grinders without additional options is shown in the figure:

Electrical diagram of an angle grinder. Photo source here

Here the two, not interconnected stator windings, through a switch, which has a design by hand start button, are connected to a voltage source (home network). Next, each of the windings with special contacts are connected to the graphite brushes, which are pressed against the surface of the collector with the help of springs. The ends of the rotor windings are in turn connected to the fins of the collector to form a closed electrical circuit.

The speed regulator is connected in the gap between the on/off button and the stator windings inside the angle grinder housing. If designed as a separate unit, it can often be located in a break in the mains cable.

What is this function, principle of operation, circuit diagram, advantages of angle grinder with a regulator

angle grinder, not equipped with a speed control device, works exclusively at the maximum speed of rotation. Equipped with this option allows you to reduce the speed to a value that allows high-quality processing of materials that is not possible at maximum mode.

The basis of the electronic block of the speed regulator is a modified principle of dimmer, where the change in power occurs by manually changing the value of the variable resistor. By means of electronic control of the current on the working shaft of the spindle, a torque is maintained, which ensures the performance of the angle grinder. The main working elements of such a circuit can be either a semiconductor device simistor, or a more advanced version with an integrated circuit.

Wiring diagram without power controller

The wiring diagram of ordinary household grinders without additional options is shown in the figure:

Electrical diagram of the angle grinder. Photo source here

Here the two unconnected stator windings are connected to the voltage source (mains) through a switch, which has a hand-operated start button in its design. Then each of the windings is connected with special contacts to the graphite brushes, which are pressed to the surface of the collector with the help of springs. The ends of the rotor windings, in turn, are connected to the fins of the collector to form a closed electrical circuit.

The speed regulator is connected in the gap between the on/off button and the stator windings inside the angle grinder housing. In the case of the design as a separate unit, it can often be in the breakage of the mains cable.

Design, electrical circuit diagram of angle grinder with a speed regulator

The factory-made speed regulator is located inside the angle grinder’s housing and is integrated into the electrical circuitry as follows:

Controller wiring diagram. Source here

The connection scheme is quite simple: the red wire is connected to one of the switch contacts, the blue wire through the second contact of the starter is connected to one of the two stator windings, and the black wire is directly shorted to the other winding.

When you connect the regulator, made by your own hands or ready-made, purchased in a store to the angle grinder, where it is not provided by the manufacturer, it is not always possible to fit it inside the housing. Practice shows examples of execution of the regulator as a separate unit in the gap of the mains cable. Users perform it as a mobile universal device, which is applicable to other types of power tools (drill, torch).

Other functions: Soft start and more

Makita 9565CVK angle grinder (angle grinder) with soft start and speed regulation. Photo 220Volt

In addition to the turnover control device and their electronic stabilization, which increase the range of work performed, the angle grinder can be equipped with other useful options.

• The soft starter reduces the extra effort on the part of the user, as the dynamic loads resulting from the sharp acceleration of the spindle greatly contribute to this. Particularly important for powerful angle grinders with a large mass of inertia. This option increases working comfort, reduces the risk of injury and increases reliability of parts and components.
• Automatic balancing mechanism reduces vibration and chatter that result from uneven wear of the tool.
• Jamming protection, which shuts off the current supply to the coils of the angle grinder during an unintended forced stop of the electric drive. Prevents overheating of the motor and its failure.
• In order to reduce the risk of injury, e.g. in the event of a sudden power outage followed by a similarly unexpected restart, a restart safety device is installed. The angle grinder will only start up again after the user has pressed the safety stop.
• If the nature of the work does not allow you to wait long for the rotating spindle to stop, the additional braking option will help stop it as quickly as possible.
• Problems arising when replacing the work tool, even with a special wrench, are solved by using a special quick-clamp nut. It enables the tooling change in the shortest possible time.

Testing the electronic device

Check the unit before connecting it to the angle grinder. Take the overhead power socket. Insert 2 wires into it, one of which is connected to the board and the other to the mains cable. Connect another wire to the circuit board. As you can see, the regulator is connected in series to the electric circuit. Connect a light bulb to the power circuit and test the unit.

Connecting the regulator to the angle grinder

The frequency converter is connected to the tool in series. If there is space in the handle of the angle grinder, you can place the device there. The circuit, assembled by means of hinged mounting, is glued with epoxy, which will serve as an insulator and protection against vibrations. Move the variable resistor and plastic knob outside to adjust the RPM.