All budget options Angle grinders have several disadvantages. Firstly, there is no soft start system. This is a very important option. Surely all of you have plugged this powerful power tool into the network, and when you start it, you have observed how the intensity of the light bulb, which is also connected to this network, drops.

This phenomenon occurs due to the fact that powerful electric motors consume huge currents at the moment of starting, due to which the network voltage sags. This can damage the tool itself, especially those made in China with unreliable windings that may one day burn out during startup.

That is, the soft start system will protect both the network and the tool. In addition, at the moment of starting the tool, a powerful kickback or push occurs, and if a soft start system is implemented, this, of course, will not happen.

Secondly, there is no speed regulator, which will allow you to work with the tool for a long time without loading it.

The diagram presented below is from an industrial design:

It is introduced by the manufacturer into expensive devices.

You can connect not only the grinder to the circuit, but also, in principle, any devices - drills, milling machines and lathes. But taking into account the fact that the tool must have a commutator motor.

This will not work with asynchronous motors. A frequency converter is required there.

So, you need to make a printed circuit board and start assembling.

A dual operational amplifier LM358 is used as a regulating element, which, using transistor VT1, controls the power triac.

So, the power link in this circuit is a powerful triac of the BTA20-600 type.

There was no such triac in the store and I had to buy a BTA28. It is a little more powerful than what is shown in the diagram. In general, for motors with a power of up to 1 kW, you can use any triac with a voltage of at least 600 V and a current of 10-12 A. But it is better to have some reserve and take 20 A triacs, they still cost a penny.

During operation, the triac will heat up, so it is necessary to install a heat sink on it.

To avoid any questions about the fact that the engine, when starting, can consume currents that significantly exceed the maximum current of the triac, and the latter can simply burn out, remember that the circuit has a soft start, and starting currents can be ignored.

Surely everyone is familiar with the phenomenon of self-induction. This effect occurs when a circuit to which an inductive load is connected is opened.

It's the same in this scheme. When the power supply to the motor suddenly stops, the self-induction current from it can burn the triac. And the snubber circuit dampens self-induction.

The resistor in this circuit has a resistance of 47 to 68 ohms, and a power of 1 to 2 W. Film capacitor for 400 V. In this embodiment, self-induction is a side effect.

Resistor R2 provides current suppression for the low-voltage control circuit.

The circuit itself, to some extent, is both a load and a stabilizing link. Thanks to this, after the resistor it is possible not to stabilize the power supply. Although the network has the same circuits with an additional zener diode, it is pointless to use it, since the voltage at the power pins of the operational amplifier is within normal limits.

Possible replacement options for low-power transistors can be seen in the following picture:

The PCB that was mentioned earlier is only a soft starter board and does not have any speed control components. This was done on purpose, since in any case the regulator must be output via wires.

The regulator is adjusted using a 100 kOhm multi-turn trimmer resistor.

If you need a more powerful regulator, it can be assembled according to the following scheme:

If everything is in order, then after disconnecting from the network, you immediately need to check the triac by touch - it should be cold.

If everything works fine - the grinder starts smoothly and the speed is regulated - then it’s time to start testing under load.

Attached files:

Scheme for connecting an analogue CCTV camera to a TV or computer Connecting a digital CCTV camera

Today, stores have a very large selection of power tools. They all differ in price, functionality and reliability. Almost all modern models of electric drills, jigsaws, and screwdrivers have a speed regulator. But grinders with this capability are very rare, and if they exist, they are much more expensive. In order not to overpay, I decided to equip my grinder, which I bought a long time ago. In principle, a regulator is not needed for cutting metal with a cutting stone, but for grinding housings in amateur radio practice it is simply not replaceable.

Schematic diagram of the angle grinder speed controller

So, the regulator circuit. It is very simple, and there is a topic for discussing it on our forum. Even for a novice radio amateur, assembling it will not be difficult. The parts are not expensive, and they can be easily bought in a store, or desoldered from old boards (if they are there, of course). Can be assembled separately in a box with a socket. Then use it as a carrier with a power regulator. For some time this was the case for me. Afterwards, I got tired of struggling with carrying things, and I assembled the regulator in the handle of the grinder.

First you need to collect all the parts in a pile. Unscrew the handle of the grinder and think about the location of each element of the circuit. Different brands of grinders have different handles, and how you arrange everything there, and in general, whether everything will fit there is your concern. In extreme cases, you can collect it in a separate box.

The radiator was cut from a piece of aluminum. A triac was screwed 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 using surface mounting according to the diagram.

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

(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 must begin with analysis electrical diagram Bulgarians.

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?

1. 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;
2. 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. And for different types stones, different speeds are selected. Some minerals are processed at high speeds;
3. 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;
4. 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;
5. Polishing of stone and concrete surfaces, depending on the type of crowns used, is carried out on different speeds. Moreover, when the rotation speed decreases, the torque should not decrease;
6. 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.

The need for a regulator arose in connection with the need to clean various kinds of rusty pieces of iron in the country before painting them. This can be conveniently done using a metal cord brush installed instead of a cutting wheel. However, since the grinder operates at maximum speeds around 10,000 rpm, the body vibrates quite strongly, and your hands get tired quickly.

The brush itself tries to catch on various irregularities and tear the grinder out of your hands, which is very dangerous. There is also an electric sharpener, which overheats sharpened chisels and thin drills at maximum speed. And the electric stove, despite the fact that it has a thermostat, strives to turn the heated food into coal.
To resolve the issue, Ali purchased assembled board network power regulator for 2000W for 100 rubles.
After successful testing of the regulator “on the snot”, the question of design of the device arose.
These boards have already been described several times on mysku, however, the appearance of the assembled devices laid out for public display forced us to look for a more beautiful solution. I wanted to have a ready-made design that was as compact as possible. In Leroy Merlin was purchased with a preliminary estimate of 30 rubles junction box TDM 65x65x50 mm.


At the moment, these junction boxes are not available in Leroy, I will explain why the choice fell on this one:

• hinged non-removable lid
• one blank side wall
• suitable base size
• the height is sufficient to accommodate the radiator.

The most compact socket offered was the Turkish Makel Siva Ustu, which today costs 93 rubles. A piece of unnecessary computer cable was used as a network cable.


To accommodate the board, the bosses protruding from the bottom were trimmed and a hole was drilled in the side wall for the regulator slide. In fact, the board is secured in the box only by the regulator body and the standard reinforcing corner of the board. The socket is attached to the box cover with two M4 screws.


The network cable is threaded through a hole in an insulating sleeve inserted into the box body “in reverse”. This installation of the coupling prevents it from being pulled out along with the power cable during careless movements. Since the conductors of the power cable touch the radiator, an additional piece of PVC tube cut and tied with electrical tape was placed on it.


I made marks on the body of the extreme positions of the regulator.


As episodic operation for more than a year with different consumers has shown, the radiator does not get particularly hot and remains warm in a closed box during long-term operation with powerful consumers.


As for cleaning rusty pieces of iron with a cord brush for an angle grinder, such work at lower speeds has definitely become more comfortable and less dangerous. The gyroscope effect is noticeably reduced. A couple of times the cord brush got snagged in the corner, but thanks to the reduced power on the shaft, the angle grinder was able to be held in my hands without injury. And the grinder itself heats up significantly less.
PS Grinder model BLACK&DECKER (B&D) CD 115, I’ve had it for 7 years now.

A grinder, or grinding machine, is often simply necessary on the farm to perform metal work. In addition, it can be used to clean both wooden and stone materials. Difficult to imagine fulfillment industrial work without grinder. This is a tool that is suitable for both a professional in his work and an amateur in household work.

When doing work with your own hands, it is important that the power tool has soft start. This is especially true if you often have to work, and the network cannot withstand the voltage of the tool.

Budget options for angle grinders - angle grinders - have a number of disadvantages:

1. The power tool does not have the ability to have a smooth, soft start. This can lead to power outages, since the angle grinder consumes large number electricity. There is also a huge probability of damage to the electric motor and breakage of the tool after not a soft start, but a sharp, jerky one.
2. Power tools, especially simple Chinese ones, do not have a speed controller (by adjusting the speed you can ensure long operation of the tool without putting a load on it).

Therefore, when choosing a tool, it is very important to pay attention to such parameters as speed control and the presence of a soft start. In addition, when choosing an angle grinder, you should pay attention to power. The main indicator here is the volume of work performed.

If the work is not large-scale and not frequent at the household level, then a power tool with an adjustment of 125 mm and a power of between 600-900 W is suitable.

For large-scale work on an industrial scale, you should use an angle grinder that is approximately twice as powerful. More to the main indicators except technical characteristics, refers to safety. The grinder must be safe. What does it mean? Firstly, as already mentioned, the presence of a soft start, which prevents voltage surges during switching on. Automatic fuses necessary for emergency stopping of the motor during a system failure. The fuses serve as a regulator when the circle jams. Provides protection from dust. It is necessary when using an angle grinder frequently to prevent dust from accumulating in the tool.

The heat dissipation function is important. The heat sink protects against overheating. During operation, especially if the work is prolonged, the machine body is subject to strong heating so that there is no overheating and heat removal is necessary. When overloaded, the angle grinder stops - this happens during heating, approaching 200 o C. Well, balancing the disk serves to reduce unpleasant vibration and beating of the tool during operation, old worn disks are especially susceptible to this effect. Paying attention and paying attention to safety when choosing a tool and when further working with it is very important.

When choosing a tool, it is worth noting that there are grinders with one and two handles. Here you should rely solely on convenience. Two-handed models will most likely be more comfortable to hold, however, such tools are heavier in weight; one-handed models will also have to be held with two hands, but such angle grinders are smaller in size and weight.

Bosch is the leader in the power tools market. The tools of this company have all the necessary characteristics from convenience to safety. Another advantage of Bosch tools is that there is good ventilation.

Bt136 600E: voltage regulation switching circuit

Manufacturers do not burden cheap angle grinders that do not have sufficient power with voltage control switching circuits, otherwise such angle grinders would no longer be cheap. When starting the grinder, if it is smooth, the process is carried out through an adapter connected by contacts to the rectifier block. The rectifier block converts the current.

But sometimes it makes sense to modernize an angle grinder using an established scheme. The electrical circuit is assembled quite simply. It is not difficult to make, and you can, if desired, connect not only an angle grinder, but any other tool to the finished circuit. However, the tool must have a commutator motor, not an asynchronous one.

A homemade approach to creating a circuit would be as follows:

• To get started, you should download the board if you don’t have it;
• The Bt136 600E triac is used as the power link;
• During operation, the triac will heat up; to avoid this, a heat sink is installed;
• The resistors used provide resistance to current, providing current suppression;
• The regulator is adjusted using a multi-turn trimmer resistor;
• To check, you should connect a light bulb;
• After connecting, the light bulb must be turned off - the triac must be cold;
• Connecting the resulting circuit to the grinder.

If the board is connected correctly, the triac and resistors of the angle grinder should start smoothly, and the use of the rotation speed should be regulated. After this, you can test the grinder in action. Such knowledge may be needed when repairing electric motor faults. For example, when voltage increases or improper balancing occurs.

Do-it-yourself speed controller for an angle grinder

If you use your ingenuity to create a speed controller with your own hands, you can use soldered control boards from a sewing machine or vacuum cleaner. In addition, the components for the regulator are inexpensive and can be easily purchased if possible. It is worth noting that the device requires a gearbox to support a certain number of revolutions and speed. If the speeds are high, then the reason is most likely in the stator. The stator requires repair. Repairing the stator is possible at home.

The operation of the commutator motor is ensured by any type of electrical voltage. When changing the voltage power, you need to reduce or increase the number of revolutions. Changing this number helps thyristor regulator rpm

Regulator assembly steps:

• First, you need to unscrew the handle of the grinder, evaluate the place and figure out where to place the elements of the circuit (if there is no space, then you can make the device in a separate box);
• The resistor can be made of aluminum;
• Provided the triac does not heat up too much, a small radiator is sufficient;
• Next, the structure is soldered.

Finally, it is glued with epoxy resin to secure it. Homemade device can work for years. There are cases when the device accelerates at higher speeds after switching on - this means the stator winding is short-circuited. In this case, a turn short circuit occurred. The stator requires repair, most often it requires rewinding.

What are the typical malfunctions: the winding breaks or burns, a short circuit occurs, the insulating surface breaks through.

Making a speed controller

An electric angle grinder is impossible without a speed controller, so that it is possible to reduce the speed.

The regulator circuit from a physics point of view looks like this:

• Resistor – R1;
• Trimmer resistor – VR1;
• Capacitor – C10;
• Triac - DIAC;
• Triac - TRIAC.

The electronic regulator can be not only built-in, but also remote for convenience. In Bosch angle grinders, the electronics set the speed from almost 3 thousand to 11.5 thousand. There is no load on the meter's power, all indicators are taken into account. Reducing the number of revolutions and increasing them is not difficult for the tool. Adjustable rotation speeds are simply necessary when working with an angle grinder.

Making a soft start for a power tool with your own hands (video)

Only at first glance, it seems that an angle grinder may never be needed in life, that situations when it will come in handy, much less when it will have to be repaired, will not arise. Of course, you can turn to professionals, or you can identify the problem yourself and try to fix it.