Electronic softstarters for power tools Select merchandise

Soft start unit. Module for reduction of voltage supply to electric motor during start-up, which ensures soft start of the tool. Function provides sparing of both motor and mechanical parts, minimizing quick start (jerk) by smoothly bringing motor power supply voltage up to rated voltage. A tool with a soft starter has a longer life, because it gives the best reliability and durability.к. is not prone to jerks, which are increased load on the brush-collector assembly, bevel gear and pinion-shaft connections via the key. When working with a tool, consuming more than 2 kW, starting “directly”, noticeably “sag” the domestic power grid, and the weak points of the contacts, can be damaged. Also, some users prefer a tool with a soft-start function, solely out of operating comfort.

To select the module, you should consider two main parameters:

    MAXIMUM ALLOWABLE CURRENT. The most common ones are: 12 / 15 / 16 A (thyristor variety). The amperage allows you to estimate the maximum module load that the control board and the radio components in it are designed for. For ease of understanding, you can use the elementary formula to calculate I=P/U ( I. amperage (A) / P. declared power (W) / U. line voltage (V) ). On an example it looks like this: angle grinder of the power of 1000 W / 1 kW, respectively, the current of 4.6 A (1000/220 = 4,545. ). Soft starter for 12 A is more than enough for any power tool up to 2,3 kW, but many people prefer a sure margin and buy soft starter for 16 A. Also, the more amperes, the more powerful the capacitor is, which means that the tool will start more smoothly.

☝ it is important to understand that these capacities are usually exaggerated for marketing purposes. This parameter defines the power absorbed by the tool when the motor stops under load in the instant before the windings are short-circuited. Even in the case of true specifications, the power output (at idle speed) is about 50%, and under load up to 75% of the marked on the tool


In CNC machines without a soft starter, the 220 V mains voltage is applied immediately to the collector motor windings, and a higher starting current is required to bring it into operation. Soft starter provides a gradual rise in voltage and, accordingly, the start-up current also does not rise in leaps and bounds.

It is possible to provide this starting mode by using special electronic circuitry. Its main component is a semiconductor chip that controls another, more powerful semiconductor device simistor, which provides power to the electric drive of the angle grinder. Thyristors of the microcircuit work with a delay of supply voltage, until the moment when the capacitor in the circuit is fully charged. The principle of microcircuits work well with providing the soft start of lathes.

K1182, LM358 chips

The best known microcircuit for soft starter k1182. This chip was made back in Soviet times, and now it is not easy to find. There are other more affordable chips, like the LM358. Many modern angle grinder in the factory version of the device uses a chip LM358.

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The simplest regulator circuit

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

Diagram of the engine speed regulator for angle grinder

Circuit configuration

  • resistor R1 (4,7 kOhm);
  • DIAC (DB3) symmetrical thyristor;
  • symmetrical thyristor TRIAC (VT-136/138);
  • VR1 trimmer resistor (500kOhm);
  • Capacitor C1 (0.1 uF400V).

Operating principle

The circuit working principle is as follows. VR1 is responsible for the charging time of C1. When voltage is applied to the circuit thyristors are closed, the output is 0. As the capacitor is charging the voltage increases in the capacitor and opens the DIAC, which gives the voltage to TRIAC. It also opens and allows current to flow. Then both thyristors are closed and stay in this position until the full reverse charge of C1. As a result, the output is a complex waveform with an amplitude that directly depends on the operating time of the circuit C1-VR1-R1.

Speed regulator wiring diagram

Final assembly and testing of the regulator

The circuit is assembled on a printed circuit board or a copper (aluminum) radiator. At the hinged assembly is especially important place of thyristors installation (strictly on the radiator, it plays the role of heat sink). Then it is necessary to check the functionality of the circuit with an ordinary light bulb. The fluidity of filament change will be the same as in the finished speed controller for angle grinder after final assembly.

The factory models include a plastic regulating wheel, if desired, you can also buy it separately and include it in the kit of the homemade regulator. If the test was successful, the regulator is mounted on the angle grinder and cut into the power circuit of the tool.

How to install the soft starter on the angle grinder

Smooth start for angle grinders. a wide range of soft starters for power tools with two and three outputs. Low cost.

Why do you need a soft starter in angle grinder and other power tools?

Chasing after the design simplicity and cheapness, almost all manufacturers forget about the safety, it is not their fault, so dictates its conditions the market. But anyone who has worked with an angle grinder or circular saw with a disc diameter of 230 mm and without a soft starter knows how powerful and dangerous a tool it is, how much it jerks when starting. And the whole problem is the lack of a small soft starter for angle grinder, which would be smooth and perfectly safe to spin the drive of the angle grinder or circular saw. In addition, if used improperly, the soft starter of the power saw can fail prematurely. In all of the above cases, our website is designed to help you solve this problem.

The difference between the PP on two and three outputs

On our site you can buy completely different soft starters for angle grinders, both in terms of amperage, shape and type of connection. The most common soft starters XS-12/d3 are 12A and 16A, with three-wire connection (the connection diagram is always printed on the case), this connection is correct from a physical point of view, but has a small design flaw, it soft starter block angle grinder or power saw can only be inside the body of the electric tool, or in the extreme case be wired to it.

And from experience I know that many people do not want to get into the tool, or just though to make a small male/female cord which will act as a soft starter. For this purpose perfectly suitable soft starters at 12A and 15A with the connection of two wires, that is, you just break the chain and solder them there. Such a connection is not quite correct from a physical point of view, but much more practical.

For the right choice of soft starter you need to know a little more information, if you have a PP for two outputs then will not work control the speed of the power tool, if you want him to regulate was then be sure to take three outputs.

Which power tools use a soft starter?

In addition to all of us accustomed bolsters soft starters are used in the following tools:

  • angle grinder. very rarely put on 125 mm, sometimes on 189 mm and almost always on 230 mm;
  • electric saws. is installed in circular saws with a blade diameter of more than 200 mm, but not always;
  • Peorators. installed in powerful barrel professional peorators, very rarely in household, although objectively it is needed in almost all;
  • demolition hammers. practically on everything should be;
  • grinders. hardly ever installed, although you can work with them much more carefully;
  • router. practically on all should be installed, so as not to break the cutter.

As you have probably guessed, on our website you can buy all kinds of soft starters for lathes listed above. By the way, in the same category there are also many speed controllers for a variety of power tools. Our site, thanks to its wide range, easy navigation and affordable prices, you will surely like.


on the Internet you can often find a soft starter circuit, built on a fairly rare domestic chip K1182PM1R, which is not always easy to find. That’s why I propose you to assemble no less effective circuit, the key link of which is available microcircuit TL072, instead of which you can also use LM358. The time it takes the motor to reach full speed is given by the capacitor C1. The greater its capacitance, the more time is needed for overclocking, the most optimal solution is 2.2 uF. Capacitors C1 and C2 must be rated for at least 50 volts. Condenser C5. at least 400 volts. Resistor R11 will dissipate a decent amount of heat, so its power should be at least 1 watt. In the scheme you can apply any low-power transistors, T1, T2, T4 have n-n structure, you can use BC457 or domestic KT3102, T4 has a p-n-p structure, in its place will work BC557 or KT3107. T5. any suitable in power and voltage triac, for example, BTA12 or TC-122.

Soft starter controller for machine tools with your own hands

Greetings, DIYers! And today we have a small home-made device, which will make any homemade machine more convenient and safer. This kit was written by AlexGyver.

It all started with the fact that the author began to use the drill stand more often, as not always possible to drill a hole perpendicular to the surface of the workpiece. In this stand there is a cheap drill without built-in RPM regulator, and in the simplest case, to work with this thing you need to clamp the trigger and put on the latch, but almost all drills already have it.

And the problem is that the maximum RPM is too high even for drilling aluminum, not to mention stainless steel and other hard-drilled metals and alloys. As for the convenience of turning it on, the drill can be left on with the button depressed and turned on with the button on the socket. Convenience is questionable, and immediately give the maximum power is also not very cool for the motor, not for the drill, not for the construction of the rack. That is, it lacks a soft start. But if you take, for example, a home-made drilling machine with a powerful motor and a heavy rotor, then it just needs a soft start. A triac and a simple circuit will be enough to control a motor which is not three-phase.

If you, like the author, do not like to solder, the Chinese have ready-made triac dimmers for 3 kW of power.

If you connect the drill through it, you get the speed control. The link to such a dimmer the author left in the description below the video (link SOURCE at the end of the article). It costs a penny, much cheaper than assembling it from components in our stores. If you only want to have a drill stand, it’s easier to get a drill with a power regulator.

In the beginning the author set a goal to build a device which will perform the following functions:

Soft-start motor, with adjustable acceleration time; 2. Acceleration to the set value, which is limited by the potentiometer, i.e. the knob; 3. You can change the RPM with the same knob while working; 4. The start will be from the logic button, the voltage of which is 5V, that is, the button will be safe for wet hands, and can be small and weak; 5. To start the machine, the button will have to be held for a while. That is, from a random click the motor will not start.

To build such a machine controller is possible on analog components, but unfortunately the author is not versed in this, and all these functions proposes to implement on a microcontroller. And of course the circuit would be about 10 times simpler. As a microcontroller, we will have a platform arduino nano. It costs 150.

Also this project can be run on a Digispark board which costs a hundred. The circuit works on 5 volts, you can power it from a USB charger for your smartphone, but the author is planning to make a compact device. So he decided to use this mini power supply.

Next we need a 10k resistor and a pushbutton. And actually we need a power part, which will supply current to the motor.

The circuit can be soldered in 15 minutes on a breadboard. Also, especially for those who do not like to solder the schematics, the Chinese have a ready-made board for the same circuit, but it’s unfortunately, huge, and we will not use it.

And now we need to download the firmware and load it into the board. At the link in the description under the author’s video, go to the project page and download the archive.

Next, using the mega detailed instructions there on the author’s site, we load the firmware into one of the two boards. They work exactly the same. The only setting we are interested in in the firmware is the time to reach full power (in milliseconds).

Now let’s assemble the circuit and see how it all works. Of course there are two circuits for different boards.

What soft starter should I choose for my power tool

You can purchase the controller module in specialized stores or online stores. In recent years, most consumers order such SPM for their tool from a popular Chinese Internet resource called Ali Express.

DeWalt DW745 soft start module install

As a rule, SPDs are installed on power tool models that are equipped with an electric motor of higher power. Most often, such power tool as an angle grinder is equipped with a soft drive system. However in this case, if necessary, the user can buy a special soft starter module and install it on any power tool, which is at its disposal.

When selecting such a module, first of all one should take into account the nominal value of the starting current necessary for work, starting the electric motor. Simply speaking, when choosing such a device, you should primarily take into account indicators of electric motor power, which is equipped with a tool. Besides, when you choose a controller, it is desirable to determine the time needed to start and also to stop the motor completely. It is also desirable to pay attention to the dimensions of such a module and previously study the wiring diagram.

Besides, soft starter modules come in two-out and three-out versions. Models with two outputs are more convenient and practical, but they are less durable, compared to counterparts equipped with three outputs. In addition, the module with two outputs is quite possible to install on the carrier, to which you can then connect a variety of equipment.

Checking the work

Check the device in operation. Watch out! All elements of the circuit are under direct voltage of 220 volts! Life Threatening! Finely assembling the device.

In order not to confuse this device with a simple extension cord, it should be marked in any way. I did it with a self-adhesive price tag and some tape.

Please watch the video of this device. This video shows graphically how the behavior of the device changes during startup. Good luck with your work and your worries.

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