DIY! Speed regulator for angle grinder with their own hands

angle grinder, or angle grinder (angle grinder) as it is officially called, sometimes contains a built-in speed controller. Some models do not have one. Speed control is not just a matter of convenience, but often a necessity. Different materials require different cutting or grinding speeds and if the machine does not provide them, at least the quality of the work is seriously reduced.

Collector motors with series excitation are used in lathes with a speed controller. They can be operated with DC or AC current. This type of motor is easily adjusted by changing the current in the circuit.

Because modern regulators use pulse-controlled key operation, they cool down only slightly and can even be built into small tools. A potentiometer is used for adjustment, the knob of which is led to the handle of the machine.

Why control the speed of the blade?

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

  • ceramic: 10,000 rpm;
  • Metal: 8000 rpm;
  • Hard 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 grinders, power under 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.

Soft start units with three wires

By the way, be careful, there are similar devices, but with three wires. For example XS-12/D3.

Or other models that look similar to the KRRQD.

But they are made on a slightly different principle and should be installed after the START button, in the tool itself. They should be energized only when the start button of the angle grinder is closed and immediately disappear when it is released.

Phase goes to pin “A”, zero to pin “C”. Then the phase control output wire goes to the motor (this is just the third wire).

Without the button, the machine would be permanently energized by 220 V, which is not permissible.

There is no such thing in two wire unit, because it is connected in the circuit breaker, and voltage (potential difference) is applied to it only at the moment of starting and running of the tool.

Another thing is the so-called electric brake or the brake winding on the crosscutters. It may not work with a 3-wire external controller, but it will with the 2-wire model.

The simplest diagram of a regulator

The circuit diagram of a speed controller for an angle grinder is assembled on a printed circuit board or in hinged mounting. And the printed circuit board, too, can be made by yourself with the help of textolite and bleach for etching. A mixture of hydrogen peroxide, salt and citric acid can be used instead of iron.

Diagram of the engine speed regulator for angle grinder

Circuit Diagram Configuration

  • resistor R1 (4.7 kOhm);
  • DIAC (DB3) symmetric thyristor;
  • symmetrical thyristor TRIAC (VT-136/138);
  • Adjusting resistor VR1 (500kOhm);
  • Capacitor C1 (0.1 uF400V).

Principle of operation

The principle of the circuit is built as follows. VR1 is responsible for the charging time of C1. When the circuit is energized the thyristors are closed and the output is 0. As the capacitor charges, the voltage in the capacitor increases and opens the DIAC which gives the voltage to TRIAC. It also opens and carries current. Then both thyristors close and stay in this position until C1 is fully recharged. As a result, a complex waveform with the amplitude directly depending on the operating time of C1-VR1-R1 circuit is formed at the output.

Speed regulator wiring diagram

Final assembly and testing of the regulator

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

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The factory models are equipped with a plastic regulating wheel, if you want it can also be bought separately and included in the kit of the homemade regulator. If the test was successful, the regulator is attached to the angle grinder and cut into the power circuit of the tool.

Motor types

Motors have different features. This means that the appliance operates at different speeds of the shaft that starts the mechanism. The motor can be:

Mainly three-phase motors are found in factories or large plants. Single-phase and two-phase versions are used for home use. This electricity is enough to run household appliances.

Operating Principles

Electric motor 220V without loosing power is used to maintain the initial speed of the shaft. This is one of the main principles of this device, which is called a frequency regulator.

With it the appliance operates at a set frequency of motor rotation and does not reduce it. Also the motor speed controller 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 was asked by many people. But this procedure is quite ordinary. It is worth only to change the frequency of the supply voltage, which will significantly reduce the performance of the motor shaft. It is also possible to change the power of the motor, engaging its coils at the same time. The control of electricity is tightly intertwined with the magnetic field and the slip of the motor. For such actions use the autotransformer, household regulators, which reduce the speed of the mechanism. But it’s also worth keeping in mind that the power of the motor will decrease.

Shaft rotation

Speed controller of asynchronous electric motor is depending on the current connection to the mechanism. The essence of the operation of an induction motor depends on the magnetic coils through which the frame passes. It turns on the sliding contacts. And when it turns around by 180 degrees, the connection will flow in the opposite direction on these contacts. That way, the rotation will remain the same. But with all this action, a suitable effect will not be obtained. It will come into force after putting a couple of 10 frames of this type into the mechanism.

Collector motor is used very often. Its work is ordinary, because the current passes through directly. because of this does not lose power revolutions of the motor, and the mechanism consumes less electricity.

The washing machine motor also needs to adjust the power. For this purpose, special boards were made, which are controlled by their own work: board speed control motor from the washing machine is multifunctional use, because when you use it the voltage is reduced, but not lost power rotation.

The circuit of this board has been tested. It is only necessary to put a bridge of diodes, picking up the optocoupler for the LED. And you have to put a triac on the radiator. In the main one the regulation of the motor 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 it is necessary to consider 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, which will serve as an output for the cooling system of the computer. To prevent the circuit from burning out, you need a special blocker, which will serve as a double current value. This way this mechanism will work long term and in a suitable volume. Power regulators will give your appliances a long and long life without much cost.

Thyristors device

This model, shown in Diagram 1, uses two thyristors switched in counter-parallel, although they can be replaced by a single triac.

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

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This circuit regulates by opening or closing thyristors (triacs) at phase transition through neutral. The following methods of circuit modification are used to correctly control the commutator motor 1:

  • Setting of protective LRC circuits, consisting of capacitors, resistors and chokes.
  • Adding capacitance to the input.
  • Thyristors or triacs implementation, which 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, small weight and dimensions. The second should include the following:

  • application for motors of small power;
  • There is noise and jerking of the motor;
  • When using the triac circuit, there is a constant U on the motor.

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

Design features

The asynchronous motor does not have any distinct poles as opposed to an alternating current motor. The number of poles is determined by the number of coils in the windings of the non-moving part (stator) and the connection method. Magnetic flux in a four-coil asynchronous machine. The stator is made of special steel sheets (electrical steel), reducing to zero eddy currents, in which there is significant heating of the windings. It leads to a massive inter-turn short circuit.

The iron or rotor core is pressed directly onto 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 bars.

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Electric motors up to 100 kW use aluminum, which has a low density. for casting into the grooves of the rotor core. But in spite of such a device, the motors of this type heat up. To solve this problem, forced cooling fans are used, which are mounted on the shaft. These motors are ordinary and reliable. But motors consume a lot of 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 their own hands

If in your arsenal is an old angle grinder, do not rush to write it off. Using a simple electrical circuit, the device can easily be upgraded, adding to it the function of changing the speed. Thanks to the simple regulator, which is real to assemble with your own hands in a few hours, the functionality of the device 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 accessories and tools.

If the angle grinder is not equipped with a speed regulator, can it be installed without assistance? Most angle grinders (angle grinder), in common parlance, have a speed regulator.

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

Consideration of the different adjustments should begin with an analysis of the electronic circuitry of the angle grinder.

Simplest diagram of a grinding machine

advanced models automatically maintain the speed regardless of load, but more often there are tools with manual adjustment of disk speed. If a drill or electronic electric screwdriver used the trigger-type regulator, the angle grinder such a principle is not feasible. First. the features of the tool mean a different grip when working. In the 2-nd. the adjustment during work is not allowed, because the speed value is exposed when the motor is turned off.

How to make a dimmer controller?

A very effective and easy solution to this issue is to create a remote frequency converter. You can use a dimmer as a converter. a device for adjusting the light level. When creating an electric socket and plug are needed. It should be said that the implementation of such a device can be done in different ways. Especially easy are 2: with the use of a circuit breaker and without it.

  • Screw the 2 wires to the ends of the electrical outlet so that one is longer. After that, connect the long end to one of the contacts on the plug. Fix the end of the 2nd wire to the contacts of the dimmer and connect its other end to the 2nd contact of the plug.
  • When using the second option is required to make a number of modifications to the scheme, but specifically to place on the cord between the plug and dimmer automatic. In most dimmers are provided with usual switches, but we need an automatic switch, which, if something goes wrong, will disconnect our device from the mains.
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So, the frequency converter of the angle grinder is ready, and for practicality it can be placed in a specialized case or fixed to the wood panel. You should only take into account that such a device. self-made, and working with electrical grid, you must be cautious.

On how to make the speed controller for angle grinder with your own hands, see the video below.

Power speed controller

Working principles

With it, the appliance operates at the set engine speed and does not reduce it. The motor speed controller also affects the cooling and ventilation of the motor. With the help of power is set by the speed, which can both increase and decrease.

The question of how to reduce the speed of the electric motor 220 V, many people wondered. But this procedure is quite simple. You only need to change the frequency of the supply voltage, which will significantly reduce the performance of the motor shaft. You can also change the power to the motor by engaging its coils. Electric control is closely related to the magnetic field and the slip of the electric motor. For such actions use mainly autotransformer, household regulators, which reduce the speed of this mechanism. But you should also remember that there will be a decrease in motor power.

The rotation of the shaft

Speed control of asynchronous electric motor depends on current connection to the mechanism. The essence of the asynchronous motor depends on the magnetic coils through which the frame passes. It turns on the sliding contacts. And when it is turned by 180 degrees, then on these contacts, the connection will flow in the opposite direction. In this way, the rotation will remain unchanged. But with this action, the desired effect will not be obtained. It will come into effect after putting a couple of dozen frames of this type into the mechanism.

The washing machine motor also needs power adjustment. For this purpose, special boards have been made, which cope with their work: board for regulating the engine speed from the washing machine carries multifunctional use, because when it is used, the voltage is reduced, but the power of rotation is not lost.

The circuit of this board is verified. It is only worth putting bridges of diodes, picking up the optocoupler for the LED. You still need to put a triac on the radiator. Basically, the adjustment of the motor 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 consider the current strength, which should not exceed 70A, and the heat dissipation when using. Therefore, you can install an ammeter to adjust the pattern. The frequency will be small and will be determined by the capacitor C2.

Next it is worth adjusting 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, which will serve as an output for the cooling system of the computer. A special locking system is required to prevent the circuit from burning out, which will double the current value. This way this mechanism will work long and at the right volume. The power controllers provide your electrical appliances with many years of service without too much expense.

What is the purpose of a low rpm angle grinder??

The integrated disc speed control option allows for gentle machining of materials such as wood or plastic. At lower speeds, comfort and safety increase. Such option is most practical in radio and electrical installations, service stations and restoration studios.

In addition, among professionals who use power tools, there is a perception that the more trivial is the construction of the device, the more reliable it is. And it’s desirable to take the additional service “stuffing” out of the borders of the angle grinder. With this approach, equipment maintenance is greatly simplified. In this regard, some firms deliberately produce individual remote electric regulators, which are connected to the mains cable angle grinder.

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