How To Connect A Grinder Without A Button

In addition to the obvious advantages over models that are powered from the mains, such angle grinders are somewhat inferior to them. Firstly, they are more expensive, and secondly, the operating time of the device is limited by the battery capacity. In addition, devices are usually only compatible with small diameter discs.

Types of grinders

In addition to the fact that grinders are divided into household and professional, angle grinders are distinguished according to the principle of operation. The difference between the two is only in what is inside and in the power source. Given these features, you can choose the appropriate option for specific operating conditions.


Safety during operation, an increase in the service life of the device is provided by the following options:

  • Soft start due to this function slows down the process of accelerating the motor to maximum speed. Because of this, the case does not jerk at startup. The instrument is easier to hold, and the accuracy of the disc guidance is increased.
  • Accidental start protection avoids unplanned start-up. Implemented by a couple of buttons on the body. The grinder is turned on by pressing both at the same time.
  • Overload protection The speed remains stable even if you press the device too hard. This prevents the motor from breaking.
  • The speed control allows you to choose the optimal speed at which the disc spins for different types of work.
  • Dust protection prevents dust and material particles from damaging the engine.
  • The anti-vibration handle makes working with the tool more comfortable and safer for the user.


These grinders do not have a motor. The disc spins because the air flow creates pressure on the blades located in the housing. They drive the axis with a circle. Models are equipped with a lever: the air is supplied by pressing it.

How To Connect A Grinder Without A Button

Since the tool is lightweight, does not overheat and is able to function as long as the user has enough strength, such a grinder can be chosen for complex construction work.

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Other attractive features:

  • The LBM engine almost does not create additional noise: only sounds from materials processing will be heard;
  • Savings in maintenance: replacement of bearings, valves is not expensive;
  • Safe to use in high humidity.

Pneumatics like the 74L214 are a good purchase for use in the construction of a country house, gazebos, furniture manufacturing and other similar work. True, it should be borne in mind that it costs a lot.


Devices that run on gasoline are large in size, since the design, in addition to the engine, is also equipped with a fuel tank. To hold such a massive device, manufacturers supplement the tool with a frame-handle, an additional handle. This type of grinder, like the previous one, makes it possible to cut concrete, stone in places where power is not supplied.

Note: A special circle is needed to cut through hard material.

Why are they good:

  1. Impressive power figures.
  2. The ability to install large drives.
  3. High productivity: cutting large structures takes less time.
  4. Autonomy.
  5. The possibility of refueling allows you to work for a long time.
  6. It is often completed with a stand, which makes it possible to use the device as a cutting machine.


  • Additional fuel costs;
  • Loud noise;
  • Harm to the environment;
  • Work will have to be stopped from time to time to cool the engine.


For grinders, designed to work with large discs, the rotation speed is 7-9 thousand revolutions per minute. For devices with smaller circles, this parameter is higher than about 12 thousand.

It should be taken into account: the characteristic is indicated by the manufacturer, taking into account idle speed. In practice, the disc spins a little slower.

Some home angle grinders, like the GL-125S, are equipped with a speed control. This option is worth choosing if you want to adjust the speed yourself.

Diagram of the smooth start of the electric motor of the grinder with your own hands

Everyone who has been using the grinder for more than one year, it broke. At first, each craftsman tried to repair the sparkling grinder himself, hoping that it would work after replacing the brushes. Usually, after such an attempt, the broken tool remains on the shelf with burned-out windings. And a new grinder is bought to replace it.

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Drills, screwdrivers, hammer drills, milling cutters are necessarily equipped with a speed controller. Some so-called calibration grinders are also equipped with a regulator, while conventional grinders only have a power button.

Manufacturers do not deliberately complicate low-power grinders with additional circuits, because such a power tool should be cheap. It is clear, of course, that the service life of an inexpensive tool is always shorter than that of a more expensive professional one.

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

All modernization consists in just assembling the electronic circuit and fixing it in the box. In a separate box because there is very little space in the sander handle.

A proven, working diagram is laid out below. It was originally intended to adjust the incandescence of lamps, that is, to work on an active load. Its main advantage? Simplicity.

  1. The highlight of the soft starter, the schematic diagram of which you see, is the K1182PM1R microcircuit. This microcircuit is highly specialized, of domestic production.
  2. The acceleration time can be increased by choosing a larger capacitor C3. While charging this capacitor, the electric motor picks up speed to the maximum.
  3. There is no need to replace the resistor R1 with a variable resistance. The 68 kΩ resistor is optimally matched to this circuit. With this setting, you can smoothly start a grinder with a power of 600 to 1500 watts.
  4. If you are going to assemble a power regulator, then you need to replace the resistor R1 with a variable resistance. A resistance of 100 kOhm or more does not lower the output voltage. By short-circuiting the legs of the microcircuit, you can completely turn off the connected grinder.
  5. By inserting a semiconductor VS1 of the TC-122-25 type, that is, at 25A, into the power circuit, you can smoothly start almost any commercially available grinder with a power from 600 to 2700 W. And there is a large margin of power in case the grinder is jammed. To connect grinders with a power of up to 1500 W, the imported semistors BT139, BT140 are enough. These less powerful electronic keys are cheaper.
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The semistor in the above circuit does not open completely, it cuts off about 15V of the mains voltage. Such a voltage drop does not affect the operation of the grinder in any way. But when the semicistor heats up, the revolutions of the connected instrument are greatly reduced. This problem is solved by installing a radiator.

This simple circuit has one more drawback, its incompatibility with the speed control installed in the instrument.

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

If experience allows and there is a desire, you can assemble a more complex soft start circuit. The circuit diagram below is standard for the XS12 module. This module is installed in the power tool at the factory.

If you need to change the speed of the connected electric motor, then the circuit becomes more complicated: a trimmer is installed at 100 kOhm, and an adjusting resistor at 50 kOhm. Or you can simply and roughly introduce a 470 kOhm variable between the 47 kOhm resistor and the diode.

In parallel with the capacitor C2, it is desirable to connect a 1 MΩ resistor (it is not shown in the diagram below).

The supply voltage of the LM358 microcircuit is in the range from 5 to 35V. The voltage in the power supply circuit does not exceed 25V. Therefore, you can do without an additional Zener diode DZ.

Whichever softstarter you build, never turn on a connected tool under load. Any soft start can be burned if in a hurry. Wait for the grinder to unwind, and then work.