Speed regulator for an angle grinder - to make the machine more reliable and functional. How to make a soft start and speed controller for an angle grinder. How can you regulate the speed of an angle grinder in a non-standard way

(angle grinders), commonly known among Bulgarians, have a speed regulator.

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

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

simple representation of the electrical circuit of a grinding machine

More advanced models automatically maintain rotation speed regardless of the load, but tools with a manual disk are more common. If a trigger-type regulator is used on a drill or electric screwdriver, then such a regulation principle is impossible on an angle grinder. Firstly, the features of the tool require a different grip when working. Secondly, adjustment during operation is unacceptable, so the speed value is set with the engine turned off.

Why adjust the rotation speed of the grinder disc at all?

When cutting metal of different thicknesses, the quality of work greatly depends on the speed of rotation of the disk.
If you are cutting hard and thick material, you must maintain maximum rotation speed. When processing thin sheet metal or soft metal (for example, aluminum), high speeds will lead to melting of the edge or rapid blurring of the working surface of the disk;
Cutting and sawing stone and tile at high speed can be dangerous.
In addition, the disk, which rotates at high speeds, knocks small pieces out of the material, making the cutting surface chipped. Moreover, different speeds are selected for different types of stone. Some minerals are processed at high speeds;
Grinding and polishing work is in principle impossible without adjusting the rotation speed.
By setting the speed incorrectly, you can damage the surface, especially if it is a paint coating on a car or a material with a low melting point;
The use of discs of different diameters automatically implies the presence of a regulator.
Changing a disk Ø115 mm to Ø230 mm, the rotation speed must be reduced by almost half. And it’s almost impossible to hold a 230 mm disc rotating at 10,000 rpm in your hands;
Polishing of stone and concrete surfaces, depending on the type of crowns used, is carried out at different speeds. Moreover, when the rotation speed decreases, the torque should not decrease;
When using diamond discs, it is necessary to reduce the number of revolutions, since their surface quickly fails due to overheating.
Of course, if your grinder works only as a cutter for pipes, angles and profiles, you won’t need a speed controller. And with the universal and versatile use of angle grinders, it is vital.

If you have an old angle grinder in your arsenal, don’t rush to write it off. Using a simple electrical circuit, the device can be easily upgraded by adding the function of changing the speed. Thanks to a simple regulator that you can actually assemble with your own hands in a few hours, the functionality of the device will increase significantly. By reducing the rotation speed, the grinder can be used as a grinding and sharpening machine for various types of materials. New opportunities are emerging for the use of additional attachments and accessories.

Why does the grinder need low speeds?

The built-in disc speed control function allows you to delicately process materials such as plastic or wood. At low speeds, operating comfort and safety increases. This function is especially useful in electrical and radio installation practice, in car services and restoration workshops.

In addition, among professional users of power tools there is a strong opinion that the simpler the device is, the more reliable it is. And it is better to move the additional service stuffing outside the power unit. In this situation, equipment repair is greatly simplified. Therefore, some companies specially produce remote, separate electronic regulators that connect to the machine’s power cord.

Speed controller and soft start - what are they for?

Modern grinders use two important functions that increase the reliability and safety of the tool:

speed controller - a device designed to change the number of engine revolutions in various operating modes;
soft start - a circuit that provides a slow increase in engine speed from zero to maximum when the device is turned on.

They are used in electromechanical tools that use a commutator motor in their design. Helps reduce wear on the mechanical part of the unit during switching on. They reduce the load on the electrical elements of the mechanism by putting them into operation gradually.

As studies of the properties of materials have shown, the most intense production of friction units occurs during a sharp transition from a state of rest to a mode of rapid movement. For example, one start of an internal combustion engine in a car is equivalent to 700 km of mileage in terms of wear on the piston group.

When the power is turned on, an abrupt transition occurs from a state of rest to rotation of the disk at a speed of 2.5–10 thousand revolutions per minute. Those who have worked with an angle grinder are well aware of the feeling that the machine simply “rips out of your hands.” It is at this moment that the overwhelming number of breakdowns associated with the mechanical part of the unit occur.

The stator and rotor windings experience no less load. The commutator motor starts in short circuit mode, the electromotive force is already pushing the shaft forward, but inertia does not yet allow it to rotate. A jump in starting current occurs in the coils of the electric motor. And although they are structurally designed for such work, sooner or later a moment comes (for example, during a power surge in the network) when the winding insulation cannot withstand and an interturn short circuit occurs.

When soft start circuits and changes in engine speed are included in the electrical circuit of the tool, all of the above problems automatically disappear. Among other things, the problem of voltage “dip” in the general network at the moment of starting a hand tool is solved. This means that the refrigerator, TV or computer will not be at risk of “burning out”. And the safety circuit breakers on the meter will not operate and cut off the current in the house or apartment.

The soft start circuit is used in angle grinders of medium and high price categories, the speed control unit is used mainly in professional models of angle grinders.

Adjusting the speed allows you to process soft materials with an angle grinder, perform fine grinding and polishing - at high speed, wood or paint will simply burn.

Additional electrical circuits increase the cost of the tool, but increase the service life and level of safety during operation.

How to assemble a regulator circuit with your own hands

The simplest power regulator, suitable for an angle grinder, soldering iron or light bulb, is easy to assemble with your own hands.

Electrical circuit diagram

In order to assemble a simple speed controller for an angle grinder, you need to purchase the parts shown in this diagram.

Schematic diagram of the speed controller

R1 - resistor, resistance 4.7 kOhm;
VR1 - trimming resistor, 500 kOhm;
C1 - capacitor 0.1 µF x 400 V;
DIAC - triac (symmetrical thyristor) DB3;
TRIAC - triac BT-136/138.

Circuit operation

Trimmer resistor VR1 changes the charging time of capacitor C1. When voltage is applied to the circuit, at the first moment of time (the first half-cycle of the input sinusoid), triacs DB3 and TRIAC are closed. The output voltage is zero. Capacitor C1 charges and the voltage across it increases. At a certain point in time, specified by the R1-VR1 chain, the voltage on the capacitor exceeds the opening threshold of the triac DB3, the triac opens. The voltage from the capacitor is transmitted to the control electrode of the TRIAC triac, which also opens. Current begins to flow through the open triac. At the beginning of the second half-cycle of the sinusoid, the triacs are closed until capacitor C1 is recharged in the opposite direction. Thus, the output produces a pulse signal of complex shape, the amplitude of which depends on the operating time of the C1-VR1-R1 circuit.

Assembly order

Assembling this circuit will not be difficult even for a novice radio amateur. Spare parts are available and can be purchased at any store. Including desoldering from old boards. The procedure for assembling the regulator using thyristors is as follows:

How to connect the device to an angle grinder, options

The connection of the regulator depends on what type of device is selected. If a simple circuit is used, it is enough to mount it into the power supply channel of the power tool.

Installing a homemade board

There are no ready-made installation recipes. Anyone who decides to equip an angle grinder with a regulator places it in accordance with their goals and model of the tool. Some people insert the device into the handle of the holder, others into a special additional box on the body.

In different models, the space inside the angle grinder body may be different. Some have enough free space to install a control unit. In others, you have to take it to the surface and attach it in a different way. But the trick is that, as a rule, there is always a certain cavity in the back of the instrument. It is designed for air circulation and cooling.

Cavity at the back of the device

This is usually where the factory speed controller is located. A DIY diagram can be placed in this space. To prevent the regulator from burning out, the thyristors should be installed on the radiator.

Video: soft start plus and engine speed adjustment

Features of installation of the finished block

When purchasing and installing a factory regulator inside an angle grinder, most often you have to modify the body - cut a hole in it to allow the adjustment wheel to come out. But this may adversely affect the rigidity of the casing. Therefore, it is preferable to install the device outside.

The adjustment wheel changes the speed

The numbers on the adjustment wheel indicate the number of spindle revolutions. This value is not absolute, but conditional. “1” - minimum speed, “9” - maximum. The remaining numbers serve as a guide for regulation. The location of the wheel on the body varies. For example, on the Bosch PWS 1300–125 CE, Wortex AG 1213–1 E or Watt WWS-900 angle grinders, it is located at the base of the handle. On other models, such as the Makita 9565 CVL, the adjustment wheel is located at the end of the housing.

The connection diagram of the regulator to the angle grinder is not complicated, but sometimes it is not so easy to stretch the cables to the button, which is located at the other end of the device body. The problem can be solved by selecting the optimal wire cross-section or by placing it on the surface of the casing.

The regulator is connected according to the diagram

A good option is to install the regulator on the surface of the device or attach it to a network cable. Not everything always works out on the first try; sometimes you have to test the device and then make some adjustments. And this is easier to do when access to its elements is open.

Important! If you have no experience working with electrical circuits, it is more advisable to purchase a ready-made factory regulator or angle grinder equipped with this function.

Attaching to the power cord

Device Instruction Manual

The basic rule when operating an angle grinder with a homemade speed controller is to adhere to the work and rest schedule. The fact is that an engine operating at a “regulated” voltage gets especially hot. When grinding at low speeds, it is important to take frequent breaks so that the commutator windings do not burn out.

It is also highly recommended not to turn on the tool if the speed regulator is set to minimum - the reduced voltage will not be enough to rotate the rotor, the collector lamellas will remain in short circuit mode, and the windings will begin to overheat. Unscrew the variable resistor to the maximum, then, turning on the angle grinder, reduce the speed to the desired value.

Following the correct order of activation and adjustment will allow you to operate the angle grinder for an unlimited period of time.

In addition, you should understand that adjusting the speed of rotation on an angle grinder occurs on the principle of a water tap. The device does not increase the number of revolutions, it can only decrease them. It follows from this that if the maximum nameplate speed is 3000 rpm, then when a speed controller is connected, the angle grinder will operate in a range lower than the maximum speed.

Attention! If the angle grinder already contains electronic circuits, for example, it is already equipped with a speed controller, then the thyristor controller will not work. The internal circuits of the device simply will not turn on.

Video: homemade angle grinder speed controller

Equipping the angle grinder with a circuit for adjusting engine speed will increase the efficiency of using the device. and expand its functional range. This will also save the technological resource of the grinding machine and increase its service life.

tehznatok.com

Speed controller for an angle grinder: how to reduce speed and make a smooth start

Power tools occupy one of the main places in our workshop. Each electrical device performs all functions according to technical specifications. What else would you like? I really want the tool to last longer or not break at all. Just as a person gets used to a friend - a dog, so he gets used to an instrument.

One of the main tools is an angle grinder, which we call an angle grinder. This is a universal tool that can cut, grind, clean surfaces, saw boards, and can be adapted to many other operations.

Smooth start and rotation speed adjustment + (Video)

Smooth starting of a power tool is the main guarantee of its longevity. Remember when a light bulb burns out? Most often at the moment of switching on. Because after connecting to the electrical network, the load increases sharply. The damaged parts of the spiral cannot withstand it and it burns out.

The same processes occur in the grinder. At the moment of switching on, the current increases sharply, because the driving forces need to not only move the armature, but also quickly gain the required speed. The effect of such a hard start can be the most deplorable - winding breakage.

To reduce the likelihood of tool failure due to a hard start, it is necessary to modify the angle grinder and equip it with a small built-in soft start device.

Another modification is the rotation regulator. From personal experience, everyone knows how inconvenient it is to work with a tool that does not have rotation adjustment. If an electric drill does not have such a device, then it is difficult to select the rotation speed and feed of the drill. This leads to either jamming of the drill or its breakage.

A lathe works similarly, in which there is a whole set of special gears to adjust the rotation of the spindle. Not only the safety of the cutter, but also the quality of material processing largely depends on this.

You can combine two advantages - soft start and adjustment of shaft speed using an electronic circuit. It is quite possible to assemble it yourself and install it directly into the car body. With such a circuit, it will start smoothly without creating overloads in the windings and network. And with the same scheme, it will be possible to regulate the speed in order to select the mode of operation with any material.

If you cut metal with significant thickness and hardness, then it is necessary to maintain high speeds. But when processing surfaces of low-melting materials, high speed will do more harm than help. It needs to be reduced. It is dangerous to work with stone or tiles at high speed. And here it needs to be reduced.

Even when grinding the disk, the rotation speed must be proportionally changed, because the linear speed of the disk edge will decrease. You cannot do without a speed controller when working with a diamond-cut disk, because at high temperatures it is destroyed very quickly.

Everything suggests that if the grinder does not have a speed controller, then one must be made and installed in the car.

How to make a speed controller with your own hands + (Video)

In order not to complicate the perception of the operating principle with complex terms, the fundamental operation of the circuit can be explained simply. It has a sensitive element that reads the load value. Depending on the read value, this element controls the locking device.

The operating principle is similar to that of a water tap. In this case, you are the sensing element that controls the water tap. The flow of water, depending on the need, becomes more or less. The same process occurs with current.

It is necessary to correctly understand the point that we cannot in any way increase the rotation speed beyond that indicated in the characteristics of the angle grinder. We can only lower the speed. If the maximum rpm is 3000, then the range in which we can adjust the rpm will be below this value.

In the simplest version, you can use a thyristor regulator circuit. He will both feel and regulate. Two in one. This circuit has only five parts. It is very compact and easily fits into the case. Such a regulator will not operate from zero speed, but this is not necessary for an angle grinder.

If lower speeds are needed in operation, then it is necessary to use another circuit on an integrated circuit, where the locking element will be a triac. Such a circuit will be able to regulate the speed from almost zero to the desired value.

In both schemes, the main load falls on the locking element. It must be designed for voltages up to 600 V and currents up to 12 A. If your grinder is more powerful than 1 kW, then the locking element must withstand a load of up to 20 A.

All parts of the thyristor circuit can be placed on a printed circuit board or simply mounted. According to the second option, the parts are soldered on a printed circuit board. A printed circuit board can be manufactured using different methods. It can be etched from foil PCB, you can even cut it out with a cutter, but it will turn out very roughly. In principle, you can ask a radio amateur you know to make it for a very modest reward.

Radio-electronic elements are inserted into the manufactured printed circuit board. They can be purchased in specialized stores or at radio markets. The ratings of each should not differ in rating and rated power. It is advisable to install a thyristor or triac on a heat sink - an aluminum or copper radiator.

When the finished board is ready, you need to choose a convenient place in the grinder body to install it. It is advisable to install it so that it is convenient to use and so that it does not interfere with the work process.

Before installing the circuit in the car, it must be checked. To do this, instead of an angle grinder, you need to connect a regular incandescent lamp to the output. An example with a power of 60 - 40 W at 220 V is suitable. The performance will be obvious by the change in the glow of the light bulb.

Now all that remains is to mount the device in the chosen location and perform a test run of the angle grinder. It will stop breaking out of your hands during startup, and the speed will be smoothly regulated by rotating the regulator.

instrument-blog.ru

How to make a speed controller for an angle grinder with your own hands, how to reduce or increase speed + video instructions

Do you have an angle grinder, but no speed controller? You can make it yourself.

Speed controller and soft start for grinder

Both are necessary for reliable and convenient operation of the power tool.

What is a speed controller and what is it for?

This device is designed to control the power of an electric motor. With its help you can regulate the speed of rotation of the shaft. The numbers on the adjustment wheel indicate a change in the rotation speed of the disk.

Angler speed regulator

The regulator is not installed on all angle grinders.

Grinders with speed controller: examples in the photo

Herz HZ-AG125EV Stayer SAG-125–900 Makita 9562CVН Flex LE 9–10 125 Bosch PWR 180 CE ASpro ASpro-A1 Hitachi G14DSL Metabo PE 12–175 DeWALT DCG412M2 EIBENSTOCK EWS 400

The lack of a regulator greatly limits the use of the grinder. The rotation speed of the disk affects the quality of the grinder and depends on the thickness and hardness of the material being processed.

If the speed is not regulated, then the speed is constantly kept at maximum. This mode is only suitable for hard and thick materials, such as corners, pipes or profiles. Reasons why a regulator is necessary:

Thin metal or soft wood requires a lower rotation speed. Otherwise, the edge of the metal will melt, the working surface of the disk will become washed out, and the wood will turn black from the high temperature.
To cut minerals, it is necessary to regulate the speed. Most of them break off small pieces at high speed and the cutting area becomes uneven.
To polish cars, you do not need the highest speed, otherwise the paintwork will deteriorate.
To change a disk from a smaller diameter to a larger one, you need to reduce the speed. It is almost impossible to hold a grinder with your hands with a large disk rotating at high speed.
Diamond blades should not be overheated to avoid damaging the surface. To do this, the speed is reduced.

Why do you need a soft start?

The presence of such a launch is a very important point. When starting a powerful power tool connected to the network, a surge of inrush current occurs, which is many times higher than the rated current of the motor, and the voltage in the network sags. Although this surge is short-lived, it causes increased wear on the brushes, motor commutator and all tool elements through which it flows. This can cause failure of the tool itself, especially Chinese ones, with unreliable windings that can burn out during switching on at the most inopportune moment. There is also a large mechanical jerk during startup, which leads to rapid wear of the gearbox. Such a start extends the life of the power tool and increases the level of comfort during operation.

Electronic unit in an angle grinder

The electronic unit allows you to combine the speed controller and soft start into one. The electronic circuit is implemented on the principle of pulse-phase control with a gradual increase in the opening phase of the triac. Grinders of different power and price categories can be equipped with such a block.

Types of devices with an electronic unit: examples in the table

Angle grinders with an electronic unit: popular in the photo

Felisatti AG125/1000S Bosch GWS 850 CE Makita SA5040C Makita PC5001C Flex LST 803 VR

DIY speed controller

The speed controller is not installed in all models of angle grinders. You can make a block for regulating the speed with your own hands or purchase a ready-made one.

Factory speed controllers for angle grinders: photo examples

Bosh angle grinder speed controller Bosh angle grinder speed controller Bosh angle grinder speed controller Sturm angle grinder speed controller DWT angle grinder speed controller DWT angle grinder speed controller

Such regulators have a simple electronic circuit. Therefore, creating an analogue with your own hands will not be difficult. Let's look at what the speed controller for grinders up to 3 kW is assembled from.

PCB manufacturing

The simplest diagram is presented below.

The simplest speed controller circuit

Since the circuit is very simple, there is no point in installing a computer program for processing electrical circuits just because of it. Moreover, special paper is needed for printing. And not everyone has a laser printer. Therefore, we will take the simplest route of manufacturing a printed circuit board.

Take a piece of PCB. Cut to the size required for the chip. Sand the surface and degrease. Take a laser disc marker and draw a diagram on the PCB. To avoid mistakes, draw with a pencil first. Next, we start etching. You can buy ferric chloride, but the sink is difficult to clean after it. If you accidentally drop it on your clothes, it will leave stains that cannot be completely removed. Therefore, we will use a safe and cheap method. Prepare a plastic container for the solution. Pour in 100 ml hydrogen peroxide. Add half a tablespoon of salt and a packet of citric acid up to 50 g. The solution is made without water. You can experiment with proportions. And always make a fresh solution. All copper should be removed. This takes about an hour. Rinse the board under running water. Drill the holes.

It can be made even simpler. Draw a diagram on paper. Glue it with tape to the cut out PCB and drill holes. And only after that draw the circuit with a marker on the board and etch it.

Wipe the board with alcohol-rosin flux or a regular solution of rosin in isopropyl alcohol. Take some solder and tin the tracks.

Installation of electronic components (with photo)

Prepare everything you need to mount the board:

Cut off four pins and solder them into the board. Then install the dinistor and all other parts except the variable resistor. Solder the triac last. Take a needle and brush. Clean the gaps between the tracks to remove any possible shorts. The triac with its free end with a hole is attached to an aluminum radiator for cooling. Use fine sandpaper to clean the area where the element is attached. Take heat-conducting paste of the KPT-8 brand and apply a small amount of paste to the radiator. Secure the triac with a screw and nut. Since all the parts of our design are under mains voltage, we will use a handle made of insulating material for adjustment. Put it on a variable resistor. Use a piece of wire to connect the outer and middle terminals of the resistor. Now solder two wires to the outer terminals. Solder the opposite ends of the wires to the corresponding pins on the board.

You can make the entire installation hinged. To do this, we solder the parts of the microcircuit to each other directly using the legs of the elements themselves and the wires. Here you also need a radiator for the triac. It can be made from a small piece of aluminum. Such a regulator will take up very little space and can be placed in the body of the angle grinder.

If you want to install an LED indicator in the speed controller, then use a different circuit.

Regulator circuit with LED indicator.

Regulator circuit with LED indicator

Diodes added here:

VD 1 - diode 1N4148;
VD 2 - LED (operation indication).

Assembled regulator with LED.

Assembled regulator with LED

This unit is designed for low-power angle grinders, so the triac is not installed on the radiator. But if you use it in a powerful tool, then do not forget about the aluminum board for heat transfer and the bta16 triac.

Making a power regulator: video

Electronic unit testing

Before connecting the unit to the instrument, let's test it. Take the overhead socket. Install two wires into it. Connect one of them to the board, and the second to the network cable. The cable has one more wire left. Connect it to the network card. It turns out that the regulator is connected in series to the load power circuit. Connect a lamp to the circuit and check the operation of the device.

Connecting the regulator to the grinder

The speed controller is connected to the tool in series.

The connection diagram is shown below.

Connection diagram to the grinder

If there is free space in the handle of the grinder, then our block can be placed there. The surface-mounted circuit is glued with epoxy resin, which serves as an insulator and protection against shaking. Bring the variable resistor with a plastic handle out to regulate the speed.

Installing the regulator inside the angle grinder body: video

The electronic unit, assembled separately from the angle grinder, is housed in a housing made of insulating material, since all elements are under mains voltage. A portable socket with a network cable is screwed to the case. The handle of the variable resistor is displayed outside.

Speed controller in box

The regulator is plugged into the network, and the instrument is plugged into a portable socket.

Speed regulator for an angle grinder in a separate case: video

Usage

There are a number of recommendations for the correct use of an angle grinder with an electronic unit. When starting the tool, let it accelerate to the set speed, do not rush to cut anything. After turning off, restart it after a few seconds so that the capacitors in the circuit have time to discharge, then the restart will be smooth. You can adjust the speed while the grinder is operating by slowly turning the variable resistor knob.

The good thing about a grinder without a speed controller is that without serious expenses you can make a universal speed controller for any power tool yourself. The electronic unit, mounted in a separate box, and not in the body of the grinding machine, can be used for a drill, drill, or circular saw. For any tool with a commutator motor. Of course, it’s more convenient when the control knob is on the instrument, and you don’t have to go anywhere or bend over to turn it. But here it’s up to you to decide. It's a matter of taste.

legkovmeste.ru

A grinder with a speed controller has more capabilities than a simpler version of a power tool.

If the angle grinder is not equipped with a speed controller, is it possible to install it yourself? Most angle grinders (angle grinders), commonly known as grinders, have a speed regulator.

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

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

The simplest representation of the electrical circuit of a grinding machine

More advanced models automatically maintain rotation speed regardless of the load, but tools with manual adjustment of disk speed are more common. If a trigger-type regulator is used on a drill or electric screwdriver, then such a regulation principle is impossible on an angle grinder. Firstly, the features of the tool require a different grip when working. Secondly, adjustment during operation is unacceptable, so the speed value is set with the engine turned off.

Why adjust the rotation speed of the grinder disc at all?

When cutting metal of different thicknesses, the quality of work greatly depends on the speed of rotation of the disk. If you are cutting hard and thick material, you must maintain maximum rotation speed. When processing thin sheet metal or soft metal (for example, aluminum), high speeds will lead to melting of the edge or rapid blurring of the working surface of the disk;
Cutting and sawing stone and tile at high speed can be dangerous. In addition, the disk, which rotates at high speeds, knocks small pieces out of the material, making the cutting surface chipped. Moreover, different speeds are selected for different types of stone. Some minerals are processed at high speeds;
Grinding and polishing work is in principle impossible without adjusting the rotation speed. By setting the speed incorrectly, you can damage the surface, especially if it is a paint coating on a car or a material with a low melting point;
The use of discs of different diameters automatically implies the presence of a regulator. Changing a disk Ø115 mm to Ø230 mm, the rotation speed must be reduced by almost half. And holding a grinder with a 230 mm disc rotating at a speed of 10,000 rpm is almost impossible to hold in your hands;
Polishing of stone and concrete surfaces, depending on the type of crowns used, is carried out at different speeds. Moreover, when the rotation speed decreases, the torque should not decrease;
When using diamond discs, it is necessary to reduce the number of revolutions, since their surface quickly fails due to overheating. Of course, if your grinder works only as a cutter for pipes, angles and profiles, you won’t need a speed controller. And with the universal and versatile use of angle grinders, it is vital.

Typical speed controller circuit

This is what the assembled speed controller board looks like

The engine speed controller is not just a variable resistor that lowers the voltage. Electronic control of the current strength is necessary, otherwise, as the speed drops, the power and, accordingly, the torque will decrease proportionally. In the end, a critically low voltage value will occur when, even with the slightest resistance of the disk, the electric motor simply cannot turn the shaft. Therefore, even the simplest regulator must be calculated and implemented in the form of a well-developed circuit.

And more advanced (and therefore expensive) models are equipped with regulators based on an integrated circuit.

Integrated circuit of the regulator. (the most advanced option)

If we consider the electrical circuit of the angle grinder in principle, it consists of a speed controller and a soft start module. Power tools equipped with advanced electronic systems are significantly more expensive than their simpler counterparts. Therefore, not every home craftsman is able to purchase such a model. And without these electronic units, all that remains is the electric motor winding and the power button.

The reliability of modern electronic components of angle grinders exceeds the service life of motor windings, so you should not be afraid of purchasing a power tool equipped with such devices. The only limiting factor can be the price of the product. Moreover, users of inexpensive models without a regulator sooner or later come to install it themselves. The block can be purchased ready-made or made independently.

Making a speed controller with your own hands

Trying to adapt a regular dimmer to adjust the brightness of the lamp will not yield anything. Firstly, these devices are designed for a completely different load. Secondly, the operating principle of the dimmer is not compatible with controlling the electric motor winding. Therefore, you have to mount a separate circuit and figure out how to place it in the instrument body. IMPORTANT! If you do not have the skills to work with electrical circuits, it is better to purchase a ready-made factory regulator, or an angle grinder with this function.

Homemade speed controller

The simplest thyristor rotation speed controller can be easily made independently. To do this, you will need five radio elements, which are sold on any radio market.

Electrical circuit of a thyristor speed controller for your instrument

The compact design allows the circuit to be placed in the body of an angle grinder without compromising ergonomics and reliability. However, this scheme does not allow maintaining torque when the speed drops. This option is suitable for reducing speed when cutting thin sheet metal, carrying out polishing work, and processing soft metals.

If your grinder is used for stone processing, or discs larger than 180 mm in size can be installed on it, you need to assemble a more complex circuit, where the KR1182PM1 microcircuit, or its foreign equivalent, is used as a control module.

Electrical circuit for speed control using the KR1182PM1 microcircuit

This circuit controls the current strength at any speed, and allows you to minimize the loss of torque when they decrease. In addition, this scheme is more gentle on the engine, extending its life.

The question of how to adjust the speed of the tool arises when it is stationary. For example, when using a grinder as a circular saw. In this case, the connection point (machine or socket) is equipped with a regulator, and the speed is adjusted remotely.

Regardless of the method of execution, the angle grinder speed controller expands the capabilities of the tool and adds comfort when using it.

The speed regulator for an angle grinder is a useful mechanism that expands the functionality and extends the service life of the power tool.

Soft start and speed controller are mandatory devices

One of the main places in the home workshop of any self-taught craftsman is occupied by an angle grinder - an angle grinder, which is popularly called an angle grinder. With its help, you can efficiently clean a variety of surfaces, sand them, cut and saw wood products. At the same time, every fan of doing such work on his own wants to make his own (or imported) more reliable and functional. This is quite real.

The key to long-term use of the angle machine is its smooth start function. When the tool is turned on, the electrical current increases. The grinder needs not only to start the electric motor, but also to quickly gain the required speed for operation. Naturally, such a sudden load negatively affects the angle grinder components, in particular, its electrical winding. The latter often breaks off. For this reason, many grinders fail after several starts. It is possible to prevent such a problem on your own. It is necessary to modify the grinder by equipping it with a built-in soft start and speed controller. It is assembled on one chip.

Many advanced (and, of course, expensive) angle grinders are initially equipped with a function for adjusting the rotation of the working disk. In cheap models of angle grinders, as well as in older devices, such a device is not provided. And its necessity among home craftsmen is not even discussed. Why? More on this later.

Why control the speed of the disk?

If the grinder is used for cutting and cutting tiles and natural stone products, the high rotation speed of the tool literally kills the power tool. In addition, with such processing, small particles begin to crumble from the material. This significantly deteriorates the quality and appearance of the tiled or stone surface. If there is a function for selecting the required speed, processing proceeds without a hitch. And the electric tool itself is completely protected from damage.

Rotation speed is also important when working with metal products. For example, aluminum or tin blanks should be cut at minimum speed. But thick and hard metal, on the contrary, is processed at high speeds. Polishing and grinding work using an angle grinder cannot be performed effectively if the saw does not allow you to select the desired speed. You will simply ruin the surface being treated. Try sanding wood or the paintwork of a car body at high speed and you will understand what we are talking about.

As you can see, modifications to the angle grinder make the device many times more functional. It becomes possible to work with any soft materials and delicate surfaces. And most importantly, the grinder becomes almost eternal. It will function for decades!

An elementary and very reliable speed controller for an angle grinder is made with your own hands from inexpensive electrical parts. Below is a diagram that shows all the necessary elements for assembling the mechanism we are interested in on a printed circuit board.

We see that we will need:

symmetrical thyristor DIAC (DB3);
resistor R1 (its resistance should be 4.7 kOhm);
another symmetrical thyristor VT136/138 (TRIAC);
capacitor C1 (400 V, 0.1 µF);
additional resistor VR1 of 500 kOhm.

This scheme works according to the following principle. The charging time of the capacitor is changed by an additional resistor (it is called a tuning resistor). When voltage arrives at the circuit, the symmetrical thyristors are in the closed position, and zero voltage is noted at the output. When charging the capacitor, an increase in the voltage across it is observed, which leads to the opening of thyristor DB3. After which the voltage is supplied to VT136/138. This thyristor also opens, and an electric current passes through it. Then the symmetrical elements close again and remain in this state until the capacitor is completely recharged in the opposite direction. As a result, at the output we receive a pulse-type signal that is complex in shape. Its specific amplitude is determined by the operating time of the circuit capacitor - additional resistor - resistor R1.

Thyristors are usually placed on a printed circuit board. It is easy to make from PCB (foil material is used). Some craftsmen cut out the board with a cutter. It is allowed to place circuit elements using the surface-mounted method. Symmetrical thyristors are installed strictly on a copper or aluminum radiator. It plays the role of an effective heat sink. The assembled mechanism is checked using a conventional incandescent lamp of 40–60 W. Connect it to the circuit and begin adjusting the brightness of the light. If the intensity changes, it means you did everything right. Now you can mount the regulator into the body of the angle grinder. This may not be so easy to do. After all, you need to ensure that the additional mechanism does not interfere with you when using the angle grinder.

You will have to determine the installation location of the homemade regulator yourself, focusing on the design features of the angle grinder. Installation of the circuit in most cases is performed:

in an additional box installed on the device body;
into the handle of the holder;
into a small cavity (designed for cooling and air circulation) in the back of the angle grinder.

The connection of the circuit to the device is carried out by mounting it into the power supply channel of the angle grinder. I don't think you'll have any difficulties with this.

Operating an angle grinder with a homemade regulator

When using a grinder with a self-assembled circuit to select the speed of movement of the disk, you must strictly adhere to the recommended operating modes of the device. He should be given frequent breaks. This is especially important when processing any products at low speeds. This precaution is due to the strong heating of the angle grinder operating on a modified voltage. If you use an angle grinder without breaks, the collector will not withstand it, its windings will burn out.

Another important point. It is not advisable to start the grinder with the speed controller set to the minimum value. In such a situation, the rotor will not have enough voltage (it will not spin). This will lead to overheating of the electrical windings due to the fact that the collector lamellas will not exit the short-circuit mode (remain short-circuited). It will be right:

set the regulator to the maximum value;
connect the angle grinder to the network;
reduce the disk rotation speed by the amount necessary to complete the work.