How to reduce the speed in the grinder. How to make a soft start and a speed controller for an angle grinder. A grinder with a speed controller has more options than a simpler version of a power tool

In detail: do-it-yourself repair of an angle grinder speed controller from a real master for a website website.

Do-it-yourself repair of an angle grinder is a completely solvable task. The main thing is not to rush, understand the design, remember all the circumstances under which it broke down, determine what could wear out during work, diagnose and start repairing.

The grinder is called an angle grinder (angle grinder). The name of the tool is due to the fact that it was produced by the Eltos-Bulgarian plant in Plovdiv. It is intended for performing work on grinding or cutting hard material:

Good for tool sharpening.

The grinder in our time is a very necessary tool, so almost everyone has it.

There are grinders of different power: from 500 W to 2500, depending on the thickness of the circle - from 115 mm to 230 mm. The most popular in the work are angle grinders with a power of 1.2 W, and the most used disk is 125 mm thick.

Every year, the choice for this construction power tool is becoming wider, but the operating rules hardly change. And even if you always adhere to them, sooner or later malfunctions occur in the mechanism, which you can try to fix with your own hands, collecting everything you need to repair the grinder.

Any grinder consists of the following parts:

• rotor - the part of the electric motor that rotates during operation and is speed-controlled, also called the armature;
• collector - a place on the rotor where the control winding wires are located;
• brushes - parts that serve as current conductors from the cable to the collector winding;
• reducer - a mechanism that acts as a drive from a rotating rotor to a spinning disk, consists of a spindle, a bearing, two gears (a large one and a shaft gear);
• stator - part of the electric motor in which the rotor operates;
• grinder cooling impeller;
• start button;
• network cable with electric drive;
• protection casing;
• grinder body;
• additional handle.

All these details can be divided into two parts:

How to disassemble the grinder? Not such a complicated process. This does not require special knowledge, but it is necessary to do everything carefully and with caution. Each owner needs to know how to disassemble any working tool, because periodically it needs internal cleaning from dirt and dust, and its durability depends on this.

At the present time on the market, you can choose a different type of grinder, which differ in operating parameters, size, quality. Manufacturers are also different. Whatever model of grinder you purchase, all have the same assembly model of parts.

Disassembling the grinder will require a few tools, you just need a regular screwdriver or a reversible ratchet.

Having prepared a screwdriver, you can start disassembling:

1. We unscrew the screws from the case and remove one side of the product.
2. We remove the nut, thanks to which the disk is held, unscrew the bolts securing the protective casing.
3. We take the brushes off.
4. Disconnect the wires from the engine.
5. We unscrew the bolts that secure the gearbox inside, and very carefully remove it, and the rotor is also removed with it.
6. We unscrew the bolts that hold the stator, and remove it.
7. We assemble the grinder back, put everything back in place one by one and fasten it.

When disassembling the grinder, it is important to remember the order in which the parts are removed in order to assemble it correctly.

In the event of a malfunction, first of all, it is necessary to exclude elementary breakdowns:

1. Bulgarian does not turn on. The angle grinder suddenly became faulty - it stopped turning on. In this case, you need to check the serviceability of the outlet, then the plug and the power cord, perhaps the drive simply does not work due to the fact that current does not enter the product.
2. The cable with the plug is intact, but the drive does not work. You need to check the start button. It is easier to repair the grinder switch by buying a new button and replacing it. Since it is rarely subject to repair, basically, the plastic pull of the switch breaks inside. If you want to experiment, you can disassemble it by numbering the contacts, and put everything back in place so that after assembly there is no short circuit.
3. The above parts are intact, and the angle grinder does not want to work - so it's time to check the brushes. Perhaps it's time to change them in the grinder. Brushes from work are constantly heated, so they wear out quickly and more often than other parts need to be replaced, and in pairs.

Having eliminated all minor breakdowns, it is necessary to understand why the tool does not want to turn on and how to repair it. Most likely, the malfunctions are serious, requiring additional knowledge. This happens if:

• the body is deformed;
• jammed one of the bearings;
• armature or stator does not work;
• broken or worn teeth at the gear of the gearbox;
• the collector is out of order;
• the control electronics sensor does not show signs of life.

If it is determined that the malfunction occurred in the mechanical part of the grinder, then you need to pay attention to the condition of the large gear located on the shaft and the bushings. If the teeth are partially worn out or the shafts are wobbly, they must be replaced immediately.

The most common breakdowns

Malfunctions grinders happen quite often. Everyone who works with this tool knows about it. What goes wrong most often?

Just one awkward press on the spindle lock button while the disc is spinning causes it to break. Sometimes it can be broken if it is used to remove a jammed disc. To prevent this from happening, you need to use an open-end wrench inserted into special holes near the disk attachment point.

It mainly occurs when jamming occurs. If a rumble is heard in the gearbox, this is a sign of just such a malfunction. When more than one tooth is broken at the gear, the angle grinder will not be able to cut the necessary material.

In order for the tool to continue working, it is necessary to change the gears, and that’s all, and even the bevel wheel. Before going to the store for spare parts, remember the manufacturer, model and power of the product.

This type of failure occurs with angle grinders that work in places where there is a lot of dust, and when they are given a rest, they are left on the ground. Dust that gets inside spoils the winding. Large loads, especially for a small power grinder, turn into a motor breakdown.

If the grinder is used to cut materials that create a lot of dust, then it is recommended to cover the ventilation holes with something.

The weakest link, and not only for angle grinders, are bearings. A high frequency of rotation quickly wears out the mechanism. The good news is that changing the bearing is easy. Replacing a sprinkled bearing with a grinder must be done on time so that there is no breakdown that cannot be fixed.

Almost all models of grinders of the lower price range lack such useful options as adjusting the spindle speed and soft start. If you have the desire and some skills, the speed controller for the grinder can be made with your own hands, although it is much easier to purchase a ready-made electronic unit for several hundred rubles. Adjusting the speed of rotation expands the capabilities of the angle grinder and allows you to use it to process soft materials at low cutting speeds. In addition to the speed controller for angle grinders, a very useful function is soft start, which smooths out a sharp increase in current in the motor windings at the moment voltage is applied to it. This prevents an abrupt increase in torque and "sagging" of the supply network. In addition, soft start reduces shock loads on the engine and grinder gearbox, which protects them from premature wear.

Any angle grinder is structurally "sharpened" to work only with a cutting or cleaning wheel of a certain diameter. In total, there are six most common diameters in the range from 115 to 300 mm, which correspond to six groups of idle speeds of the spindle. For example, grinders with circles Ø125 mm have a rotational speed of the order of 11 ÷ 12 thousand rpm, and with circles Ø150 mm - 9 ÷ 10 thousand rpm. Such values ​​of the spindle speed are due to the fact that cutting discs are designed for high-performance processing of hard materials (metal, stone, ceramics) at cutting speeds up to 80 m/s.

However, when cutting and especially grinding soft and tough materials, completely different cutting parameters are required and, accordingly, the use of a tool with a speed controller. And this applies not only to wood and plastics, but also to steels, titanium and aluminum alloys. For example, the processing of plastics and soft woods occurs at cutting speeds from 8 to 12 m/s, grinding of titanium and stainless steel alloys is within 15–20 m/s, and even ordinary steel is ground at no more than 30 m/s. Therefore, the speed of rotation of the grinding nozzles for angle grinders should be several times less than the passport one. At the same time, it should be noted that in the bulk of the angle grinder speed controllers, in essence, they are power controllers supplied to the grinder's electric motor. That is, the reduction in the number of revolutions is achieved by reducing the source power by up to 15% of the nominal value. But for grinding and cutting soft materials, this does not matter much, because in this case, little power is required initially.

Schematic diagram of the speed controller

Modern angle grinder speed controller circuits are built on the principle of transmitting only part of the power of one or both half-waves of alternating current with a semiconductor switch. Triacs (symmetric thyristors) are used as a half-wave length regulator in such devices, therefore they are sometimes called triac regulators. The figure below shows a simplified diagram of such a device, sufficient to explain the principle of its operation, and to the right of it - diagrams of the full cycle of the alternating current before and after regulation. Here, the shaded areas correspond to the power that is transferred to the electric motor from the power source through the triac controller.

In the diagram, the wave icon indicates the source of alternating voltage, and the letter "M" indicates the grinder's engine. In a simplified form, the regulator includes two RC circuits, a dinistor and a triac. When the switch K1 is pressed, an alternating voltage is applied to the electric motor M and the regulator circuit. The current flowing through the variable resistor R1 begins to charge the capacitor C1. Its charge time is determined by the resistance of the resistor R1, which depends on the position of its slider, which, in fact, sets the time parameters for the operation of the regulator. After the capacitor is fully charged, the voltage at the point of its connection to the dinistor rises to the nominal value, the dinistor opens and supplies voltage to the control electrode of the triac. Capacitor C1 is discharged. This moment on the regulator operation diagram is shown by a bold vertical line. After the triac is opened, voltage is applied to the grinder's engine in the first half-cycle.

When the polarity of the alternating current is reversed, the voltage passes through zero, so the dinistor and triac close. In the negative half-cycle, everything repeats, and the switching on of the triac also occurs with a delay determined by the parameters of the R1C1 chain. The regulator, even at idle, works with a certain delay in turning on the triac. This is due to the fact that, although the moment the current is applied by the resistance R1 to the capacitor C1 corresponds to the voltage crossing through zero, it still has to rise to the level of the breakdown voltage of the dinistor. The figure below shows the dependence of the power supplied to the grinder's engine on the time shifts of the control pulses of the dinistor. In the first case, the resistance of the resistor R1 is minimal, so C1 is charged quickly, and in the second case, the resistance is maximum, so the capacitor charges more slowly.

What is soft start

The smooth start of an angle grinder is an increasing supply of voltage to its engine, at which it accelerates without jumps in starting current and with a gradual increase in torque. This mode protects the supply network from excessive power take-off and prevents its “sagging”. This is especially true when the grinder is powered from autonomous voltage sources. In addition, it protects the motor windings from excessive currents, which can lead to their breakdown. With a soft start, the grinder gearbox does not experience shock loads, which protects it from premature wear.

The electronic circuit that ensures the smooth start of the grinder is built on the same principle as the speed controller circuit. It also uses a triac to limit power to the motor. But unlike the rotation speed controller, the control pulses to the triac are formed not by manually setting the resistance in the RC circuit, but by an electronic circuit that generates a sequence of pulses with a decreasing delay duration. The diagram below shows how the pulse shift time is reduced and the power supplied to the grinder's engine increases.

Since the soft starter and the speed controller work on the same circuitry, electronic units are produced that combine the functions of both of these devices.

Ways to connect the regulator inside the grinder body

The speed control unit is a very compact device that fits easily inside the grinder body. On the Internet, you can easily find diagrams and manuals for the manufacture of such regulators. But how expedient it is to do it yourself - everyone decides for himself, because in online stores a ready-made block can be purchased for only 300-500 rubles. The photo below shows an electronic speed controller for voltages up to 250 V and a rated current of 12 A with a standard six-position step adjustment for angle grinders. Its price without delivery is about 200-300 rubles, depending on the seller.

In the gripping part (rear handle) of the grinder, there is more than enough space to install a regulator with such dimensions. For low-power angle grinders, the free space is usually closer to its end, while for more powerful ones, between the handle and the engine or in the handle itself (see photo below). Special skills for installing such a regulator are not required, because it just needs to be included in the break in the power supply circuit of the grinder's electric motor.

The video below shows the resuscitation of an old angle grinder with its rotation speed controller. Interesting push-button control of the number of revolutions with memorization of the value after turning off the supply voltage.

Soft start connection

An electronic speed controller is mainly needed by home craftsmen to expand the grinder's capabilities in terms of grinding and processing soft materials. Professionals, as a rule, use a specialized tool for certain types of work and use angle grinders only for their intended purpose. With a soft starter, the situation is different. For a household tool with little power, this option is useful, but not required. But for professional angle grinders with drives over 1000 W, it is vital. In addition to the performance improvements mentioned above, soft start is critical to operator safety. An angle grinder with a circle Ø230 and a power of 2000 W weighs 5 ÷ 6 kg, and in order to hold it during the starting jerk, certain efforts and a stable position are required.

The soft start unit can be purchased in retail chains and independently mounted inside the housing of any angle grinder. The video below shows its installation on a new powerful angle grinder purchased by the author for cleaning work. This video is also interesting in that its author, using a pointer device, demonstrates the magnitude of the current surge when the grinder is turned on, first without a soft start, and then with this device.

The most advanced control device for the angle grinder is the speed maintenance system under load, which also acts as a speed controller and provides a smooth start. On the Internet, you can find a scheme for manufacturing such a device on the U2010B chip, but it is quite complicated even for those who have the initial skills of a radio amateur. Is it possible to purchase a ready-made block for maintaining revolutions and how much does it cost? If anyone can answer this question, please share the information in the comments.

As a rule, budget angle grinders (angle grinders), popularly called grinders, do not have adjustable electronic modules in their design, which include an engine speed controller and soft start. The owners of such grinders eventually begin to understand that their absence drastically reduces the functionality of the tool. In this case, you can refine the angle grinder by installing home-made devices on it.

When power is applied to the grinder motor, abrupt increase in speed from zero to 10 thousand and more. Those who worked with angle grinders are well aware that it is sometimes difficult to hold it in their hands when starting, especially if a large-diameter diamond blade is installed.

It is because of such abrupt increases in engine speed that the mechanics of the apparatus most often fail.

Also during start-up, a huge load is applied to the rotor and stator windings of the electric motor. Since a collector motor is installed in the angle grinder, it starts in short circuit mode: the electromagnetic field is already “trying” to turn the rotor, but it remains motionless for some time, since the inertia force does not allow it to be done. As a result, the starting current in the motor coils increases sharply. Despite the fact that the manufacturer has invested a certain margin of safety for the coils, taking into account the overloads at the start, sooner or later the insulation does not withstand, which leads to an interturn short circuit.

In addition to problems with starting, the lack of speed control causes some discomfort. For example, an angle grinder speed controller can come in handy for certain types of work:

• when grinding or polishing any surfaces;
• when installing a large diameter tool;
• for cutting some materials.

In addition, when peeling with brushes, there is a high probability of wire jamming in any slot. If the spindle speed was high, then the grinder can simply be pulled out of the hands.

If you connect a power (speed) controller with a soft start module to the angle grinder, then all the above problems will disappear, the service life of the device will increase and the safety of its use will increase.

Scheme of a homemade regulator

One of the most popular schemes for soft starting an angle grinder engine with the ability to adjust the speed is presented below.

The basis of this regulator is the KR118PM1 microcircuit, as well as triacs, which are the power part of the device. Using this scheme, you can make a power regulator with your own hands, even without special knowledge in radio electronics. The main thing is that you know how to use a soldering iron.

This block works as follows.

1. After pressing the start button of the unit, the electric current begins to flow, first of all, to the microcircuit (DA1).
2. The control capacitor begins to charge smoothly and after a while gains the desired voltage value. Due to this, the opening of the thyristors in the microcircuit occurs with some delay. It depends on the time it takes to fully charge the capacitor.
3. Since the triac VS1 is controlled by the thermistors of the microcircuit, it opens just as smoothly.

The above processes occur in periods that are reduced each time. Therefore, the voltage supplied to the motor windings does not increase abruptly, but slowly, resulting in a smooth start of the grinder.

The capacitance of the capacitor C2 determines the time for the electric motor to reach full speed. The capacitance of 47 microfarads allows you to start the engine in 2 seconds. When the angle grinder is turned off, the discharge of the capacitor C1 is carried out using a 60 kΩ resistor R1 for 3 seconds, after which this electronic module is again ready to start.

If the resistor R1 is replaced with a variable, then you will get a speed controller that will allow you to reduce the engine speed.

It is important that the VS1 triac has the following characteristics:

• the minimum current for which it is designed should be 25 A;
• the triac must be rated for a maximum voltage of 400 V.

This scheme and the regulators made according to it have been repeatedly tested by many masters on angle grinders with a power up to 2000 watts. It is worth noting that this device, thanks to the KR118PM1 chip, is designed for power up to 5000 watts. So he has a considerable margin of safety.

Ideally, in order to solder the speed controller for the angle grinder, you will need to draw a printed circuit board, etch the contacts with acid and then tin them, drill holes and solder the radio components. But everything can be made easier:

• solder all the details of the circuit on weight, that is, leg to leg;
• attach a radiator to the triac (can be made from sheet aluminum).

The regulator soldered in this way will take up less space, and it can be easily placed in the grinder body.

How to connect a regulator to an angle grinder

To connect a homemade power regulator does not require special knowledge, and any home master will cope with this task. The module is installed in the break of one wire, through which food goes to the grinder. That is, one wire remains intact, and the regulator is soldered into the gap of the second.

In the same way, you can connect a factory power regulator worth about 150 rubles, which is often purchased by craftsmen in China.

If there is very little space in the grinder, then the regulator can be placed outside of the tool as shown in the following photo.

Also, the regulator can be placed in a socket and used to reduce the speed not only of the grinder, but also of other electrical appliances (drills, sharpeners, milling or wood lathes, etc.). This is done in the following way.

The regulator is connected as described above - at the break of one of the wires of the supply cable.

The following photos show how the finished outlet will look like, which has a built-in grinder speed controller, which can be used for other electrical appliances.

Instead of a junction box, you can use any plastic case suitable size. Also, the box can be made independently by gluing pieces of plastic with a glue gun.

Do you have a 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 it, you can adjust the speed of rotation of the shaft. The numbers on the adjusting wheel indicate the change in disc speed.

The regulator is not installed on all angle grinders.

Bulgarians with a speed controller: examples in the photo

The lack of a regulator greatly limits the use of the grinder. The speed of rotation of the disc 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 angle, pipe or profile. Reasons why a regulator is necessary:

1. For thin metal or soft wood, a lower rotation speed is needed. Otherwise, the edge of the metal will melt, the working surface of the disk will become blurry, and the wood will turn black from high temperature.
2. For cutting minerals, it is necessary to regulate the speed. Most of them break off small pieces at high speed and the cut becomes uneven.
3. You do not need the highest speed to polish cars, otherwise the paintwork will deteriorate.
4. To change the disk from a smaller diameter to a larger one, you need to reduce the speed. It is almost impossible to hold a grinder with a large disk rotating at high speed with your hands.
5. Diamond blades must not be overheated so as not to spoil the surface. For this, the turnover is reduced.

Why you need a soft start

The presence of such a launch is a very important point. When you start a powerful power tool connected to the network, an inrush current occurs, which is many times higher than the rated current of the motor, the voltage in the network sags. Although this surge is short-lived, it causes increased wear on the brushes, the motor commutator, and all parts of the tool through which it flows. This can cause the tool itself to fail, especially the Chinese one, with unreliable windings that can burn out at the most inopportune moment when turned on. And also there is a large mechanical jerk at startup, which leads to rapid wear of the gearbox. This start prolongs the life of the power tool and increases the level of comfort when working.

Electronic unit in angle grinder

The electronic unit allows you to combine the speed controller and soft start into one. The electronic circuit is implemented according to the principle of pulse-phase control with a gradual increase in the opening phase of the triac. Such a block can be supplied with grinders of different capacities and price categories.

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

Angle grinders with an electronic unit: popular in the photo

DIY speed controller

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

Factory speed controllers for angle grinders: photo examples

Bosh grinder speed controller Speed ​​​​regulator grinders Sturm DWT angle grinder speed controller

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

PCB manufacturing

The simplest scheme is shown below.

Since the circuit is very simple, it makes no sense to install a computer program for processing electrical circuits because of it alone. Moreover, special paper is needed for printing. And not everyone has a laser printer. Therefore, let's go by the simplest way of manufacturing a printed circuit board.

Take a piece of textolite. Cut off the required size for the chip. Sand the surface and degrease. Take a marker for laser discs and draw a diagram on the textolite. In order not to be mistaken, first draw with a pencil. Next, let's start etching. You can buy ferric chloride, but after it the sink is poorly washed. If you accidentally drip on clothes, stains will remain 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 of hydrogen peroxide. Add half a tablespoon of salt and a sachet of citric acid to 50 g. The solution is made without water. You can experiment with proportions. And always make a fresh solution. Copper should be all etched. This takes about an hour. Rinse the board under a stream of well water. Drill holes.

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

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

Mounting of electronic components (with photo)

Prepare everything you need to mount the board:

1. Solder coil.
2. Pins in the board.
3. Triac bta16.
4. Capacitor 100 nF.
5. 2 kΩ fixed resistor.
6. Dinistor db3.
7. Variable resistor with a linear dependence of 500 kOhm.

Bite off four pins and solder them to the board. Then install the dinistor and all other parts except for the variable resistor. Solder the triac last. Take a needle and a brush. Clean the gaps between the tracks to remove possible short circuits. Triac free end with a hole is mounted on an aluminum radiator for cooling. Clean the area where the element is attached with fine sandpaper. Take the KPT-8 heat-conducting paste and apply a small amount of paste on the radiator. Secure the triac with a screw and nut. Since all the details of our design are under mains voltage, we will use a handle made of insulating material for adjustment. Put it on a variable resistor. With a piece of wire, connect the extreme and middle terminals of the resistor. Now solder two wires to the extreme conclusions. 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, too, you 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 grinder case.

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

Regulator circuit with LED indicator.

Diodes added here:

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

Assembled controller with LED.

This block is designed for low-power 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 heat transfer board and the bta16 triac.

Making a power regulator: video

Electronic unit test

Before connecting the block to the instrument, we will test it. Get an overhead socket. Insert 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 board. 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.

Testing the power regulator with a tester and a lamp (video)

Connecting the regulator to the grinder

The speed controller is connected to the tool in series.

The connection diagram is shown below.

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

Installing the regulator inside the angle grinder body: video

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

The regulator is connected to the network, and the tool is connected to a portable socket.

Speed ​​​​regulator for a 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 it 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 running by slowly turning the knob of the variable resistor.

A grinder without a speed controller is good because 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 grinder, can be used for a drill, drill, circular saw. For any tool with a commutator motor. Of course, it is more convenient when the control knob is on the tool, and you don’t have to go anywhere and bend over to turn it. But now it's up to you to decide. It's a matter of taste.

To date, the stores have a very large selection of power tools. All of them differ both in price and in functionality and reliability. Almost all modern models of electric drills, jigsaws, screwdrivers have a speed control. But grinders with such an opportunity are very rare, and if they exist, they are much more expensive. In order not to overpay too much, I decided to equip my grinder bought long ago. In principle, a regulator is not needed for cutting metal with a cutting stone, but for grinding cases in amateur radio practice, it simply cannot be replaced.

Schematic diagram of the grinder speed controller

So, the controller circuit. It is very simple, and there is a topic on our forum to discuss it. Even for a beginner radio amateur, it will not be difficult to assemble it. Parts are not expensive, and you can easily buy them in a store, or solder them from old boards (if they are there, of course). Can also be assembled separately in a box with a socket. Then use it as a carrier with a power regulator. For a while I was like that. After I got tired of competing with carriers, and I assembled the regulator in the handle of the grinder.

First you need to collect all the details in a bunch. Unscrew the handle of the grinder, and consider the location of each element of the circuit. Different brands of grinders have different handles, and how you place everything there, and indeed, whether everything will fit in there is already your concern. In extreme cases, you can collect in a separate box.

Radiator cut from a piece of aluminum. A triac was attached to it. By the way, it does not get very hot during operation, so the radiator can be made with a small area. Then I soldered all the parts by surface mounting according to the diagram.

So that during operation this whole thing does not shake and short-circuit - it is glued with epoxy. Variable resistor installed on the other side. He put on a large plastic handle. Even when working with it, it is convenient to change the speed of the grinding wheel.