Electronic circuit for starting an electric tool. Smooth start grinder. Scheme. Connecting the soft start function

Many electric tools, especially those from earlier years, are not equipped with a soft starter. Such tools are launched with a powerful jerk, as a result of which there is increased wear on bearings, gears and all other moving parts. Cracks appear in the varnish insulating coatings, which are directly related to the premature failure of the tool.

To eliminate this negative phenomenon, there is a not very complicated circuit on an integrated power controller, which was developed back in the Soviet Union, but it is still not difficult to buy it on the Internet. The price is from 40 rubles and above. It is called KR1182PM1. Works well in various control devices. But we will assemble a soft start system.

Soft starter diagram

Now let's look at the schema itself.

As you can see, there are not very many components and they are not expensive.

It will take

Chip - KR1182PM1.
R1 - 470 Ohm. R2 - 68 kilo ohms.
C1 and C2 - 1 microfarad - 10 volts.
C3 - 47 microfarads - 10 volts.

Breadboard for mounting circuit components "so as not to bother with the manufacture of a printed circuit board."
The power of the device depends on the brand of triac that you supply.
For example, the average value of the current in the open state for different triacs:

BT139-600 - 16 amps,
BT138-800 - 12 amps,
BTA41-600 - 41 amps.

Device assembly

You can put any others that you have and that suit your power, but keep in mind that the more powerful the triac, the less it will heat up, which means it will work longer. Depending on the load, you must also use a cooling radiator for the triac.
I installed the BTA41-600, you can not install a radiator for it at all, it is powerful enough and will not heat up during repeated-short-term operation, with a load of up to two kilowatts. I don't have a more powerful tool. If you plan to connect a more powerful load, then think about cooling.
Let's collect the parts for mounting the device.

We also need a “closed” socket and a power cable with a plug.

It is good to adjust the breadboard in size with large scissors. It cuts easily, simply and neatly.

Place the components on the breadboard. For a microcircuit, it is better to solder a special socket, it costs a penny, but it makes the job very easy. There is no risk that you will overheat the legs of the microcircuit, you do not need to be afraid of static electricity, and even if the microcircuit burns out, you can replace it in a couple of seconds. It is enough to take out the burnt one and insert the whole one.

We solder the parts immediately.

We place new parts on the board, referring to the diagram.

Solder carefully.

For the triac, the nests need to be slightly drilled out.

And so in order.

We insert and solder the jumper and other parts.

We solder.

We check the compliance with the diagram and insert the microcircuit into the socket, not forgetting the key.

We insert the finished circuit into the outlet.

We connect the power to the outlet and the circuit.

Please watch the test video of this device. The change in the behavior of the device at startup is clearly shown.
Good luck in your business and concerns.

As you know, the starting current of an electric motor can be several times higher than the rated current, and if the motor is powerful, turning it on causes a voltage drop in the supply network, which can cause malfunction of devices sensitive to such failures.
This fully applies to power tools, which are based on electric motors. A characteristic starting jerk when turning on a powerful hand-held power tool (it seems to be “trying to escape” from the hands) can lead to injury if used ineptly.

Schematic diagram of a device for soft start power tools

Oscillograms explaining the principle of operation of the electric motor soft start device

Device circuit board

Location of parts on the printed circuit board of the softstart system

In addition, starting modes cause increased wear of its mechanical components. These negative consequences can be avoided by implementing the so-called soft start of the electric motor, in which its rotational speed increases from zero to nominal within a few seconds.
It is this problem that the device offered to the attention of readers solves. Its prototype was an electronic unit used in hand-held power tools by some companies. As an additional function, smooth manual speed control is provided.
The device can be used in a power tool with a supply voltage of 220 V and a current consumption of up to 16 A. In practice, it is better to limit the load to a power of no more than 2.5 kW.
The described device is built by the author into a Sparky angle grinder with a power of 2.1 kW. A photo of the mounted device in its case is shown in fig. 5.

Before that, I had never made a soft starter. Purely theoretically, I imagined how to implement this function on a triac, although this option is not without drawbacks - power loss and a heat sink is needed.
Wandering through the dusty Chinese storehouses, in vain attempts to find something worthwhile, but not expensive, in the deposits of counterfeit and illiquid assets, I stumbled upon this product.

Blah blah blah

The purchase was not for the sake of purchase, but a conscious necessity. I decided to write a review to put a manual router on the table. And I have it without a soft start, it starts abruptly, self-destructing and destroying its surroundings. Are soft start and soft start the same thing? Of course, there were doubts, although I had nothing to do with thermistors, I saw them only in computer power supplies, I always thought that they react to “jumps and bursts”, that is, quickly, but “the voltage to rise slowly” and “after about five seconds" spawned a worm of doubt. Yes, and “or other high starting current machine applications.”
Since the lack of knowledge makes us wasteful and decisive, I ordered this device and did not regret it for a second.

Here is what the seller says about him:
Soft start power supply for class A amplifier, promising: 4 kW of power and 40 A through relay contacts at AC voltage from 150 V to 280 V. Size 67 mm x 61 mm x 30 mm, the seller calls it ultra-small - a-ha -Ha. As if my current milling cutter falls into the frame, even if we divide the Chinese amps by two, but in this size the board is not pushed inside the tool case.
And yes, it's a constructor. Need to solder!

The product arrived in this form, plus, for better preservation, it was wrapped in a piece of newspaper in Chinese / Korean / Japanese, which disappeared, a survey of household members and numerous servants did not clarify who and for what needs this piece was needed, so there is no photo of the newspaper, On top was another bag without any bubbles.
Soldering is easy - everything is drawn and signed.

Fee - may be useful to someone

Soldered:

back side

sketched out the concept

How it works: when turned on, R2 has a large resistance, the voltage at the load is less than 220 V, the thermistor heats up, its resistance tends to zero, and the voltage at the load reaches 220 V. Accordingly, the engine picks up speed.

At the same time, the rectified and stabilized VD2 voltage (24 V, although according to the first datasheet that came across should be 25, but volts there, volts here ...) feeds the relay switching circuit. Capacitor C3 is charged through R1, the capacitance of which determines the response time of the relay. After 5 seconds, the transistor VT2 opens, the relay contacts shunt the thermistor R2 and the engine runs at maximum power.
It was smooth on paper ... In reality, connecting this device does not provide any soft start to the engine, the thermistor heats up instantly, the motor immediately threshes for nothing, only the relay mockingly clicks after 5 seconds. I tried a 150 W motor - the same effect.

Blah bpa blah

Scolded what the world is worth a Chinese merchant. Pets, preschool children and accustomers, who were watching the experiment, fled and hid in dark corners, the mother-in-law, just in case, took a pestle out of her sleeve. But do not mislead gullible Russian buyers. He finished his drink from the bottle left over from the coronation before last, ate a cold kulebyakoy, calmed down ... He took out a payment from the garbage can, robbed the sunflower husks from it.

“If the job fails, then any attempt to save it will worsen the matter,” says Edward Murphy. “Too many people break down without even knowing how close to success they were at the moment when they lost heart,” Thomas Edison argues with him. These two quotes have nothing to do with the matter, they are given here to show that the author of the report is not just a freebie hunter and a stupid consumer of Chinese goods, but a well-read, pleasant conversationalist and intellectual. Figley. But to the point.
There were a couple of K1182PM1R microcircuits lying around in my closet on the mezzanine in a hat box.

Extract from the datasheet:

The direct application of the IC is for smoothly turning on and off electric incandescent lamps or adjusting their brightness. IS can also be successfully applied for adjusting the speed of rotation of electric motors up to 150 W(e.g. fans) and to control more powerful power devices (thyristors).

On one of them, I assembled a soft starter, which is not without flaws, but works as it should.

C1 sets the soft start time, R1 sets the voltage on the load. I got the maximum voltage at 120 ohms. At C1 100 uF, the acceleration time is about 2 seconds. By changing R1 to a variable, you can adjust the speed of the collector motor, without feedback, of course (although this is implemented on the vast majority of sold power tools). Triac VS1 any found, suitable for power. I have a BTA16 600B lying around.

back side

Everything is working.

Now it remains to cross two devices that complement each other, nullifying the shortcomings inherent in each individually.

Blah blah blah

In principle, the task is not difficult for a lively, inquisitive mind. I soldered the thermistor, and threw it away and hid it until better times, in its place I soldered two wires coming from the cathode and anode of the triac of the second board. I reduced the capacitance C3 on the first board to 22 uF, so that the relay would close the cathode and anode of the triac not after 5 seconds, but after about two.

At an air temperature of 30 degrees. With the temperature of the diode bridge 50 degrees, the zener diode 65 degrees, the relay 40 degrees.
Everything - the alteration is completed.

Blah blah blah

Another, less confident in his abilities, would have been delighted with the result, would have thrown a feast with a mountain, would have arranged a holiday with bears and gypsies. I just opened a bottle of champagne, made the girls dance round dances in the yard and canceled the Saturday spanking.

It remains only to arrange it all in the case, I already wanted to, but something at home does not have a metal plate with which the case will be attached to the table. Everything will look something like this:

My conclusions are ambiguous, estimates are biased, recommendations are dubious.
Everyone was tired, even these cats climbed into the frame all the time - they were tired of chasing. I plan to buy +21 Add to favorites Liked the review +92 +163

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

Drills, screwdrivers, rotary hammers, milling cutters are necessarily equipped with a speed dial regulator. Some so-called calibration grinders are also equipped with a regulator, and ordinary grinders have only a power button.

Manufacturers do not deliberately complicate low-power angle 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 angle grinder can be upgraded so that the gearbox and armature winding wires will no longer be damaged. These troubles mainly occur during a sharp, in other words, shock start of the grinder.

All modernization consists only in assembling the electronic circuit and fixing it in the box. In a separate box, because there is very little space in the handle of the grinder.

A tested, working circuit is laid out below. It was originally intended to adjust the incandescence of lamps, that is, to work on an active load. Her main asset? simplicity.

The highlight of the soft starter, the schematic diagram of which you see, is the K1182PM1R chip. This microcircuit is highly specialized, of domestic production.
The acceleration time can be increased by choosing a larger capacitor C3. While this capacitor is being charged, the electric motor speeds up to maximum.
No need to replace the resistor R1 variable resistance. The 68 kΩ resistor is optimally matched for this circuit. With this setting, you can smoothly start the grinder with a power of 600 to 1500 watts.
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 kΩ or more does not lower the output voltage. By short-circuiting the legs of the microcircuit, you can completely turn off the connected angle grinder.
By inserting a TS-122-25 semistor VS1 into the power circuit, that is, at 25A, you can smoothly start almost any grinder available for sale, with power from 600 to 2700 watts. And there is a large margin of power in case the grinder jams. To connect grinders with a power of up to 1500 W, imported seven-stores BT139, BT140 are enough. These less powerful electronic keys are cheaper.

The triac in the above circuit does not fully open, it cuts off about 15V of the mains voltage. Such a voltage drop does not affect the work of the grinder. But when the sevenstor is heated, the speed of the connected tool is greatly reduced. This problem is solved by installing a radiator.

This simple circuit has another drawback - its incompatibility with the speed controller installed in the tool.

The assembled circuit must be hidden in plastic boxes. The housing made of insulating material is important, because you need to protect yourself from mains voltage. You can buy a junction box at an electrical supply store.

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 XS-12 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 tuning resistor of 100 kOhm is installed, and a control resistor of 50 kOhm is installed. Or you can simply and roughly introduce a 470 kΩ variable between a 47 kΩ resistor and a diode.

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

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

Whatever soft starter you build, never turn on the tool connected to it under load. Any soft start can be burned if you rush. Wait for the grinder to unwind, and then work.

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Smooth start grinder the circuit, which is built on the KR1182PM1 microcircuit (phase control microcircuit), allows you to smoothly and safely start not only the grinder, but also any powerful power tool. The soft start circuit is quite simple and does not require any configuration.

It is possible to turn on any power tool that runs on a 220-volt power supply to the circuit without any change. Starting and turning off the electric motor of the angle grinder is carried out by the electric button of the power tool itself.

The soft start diagram for the grinder is shown in the figure below. The XP1 connector is connected to a 220-volt power outlet, and a grinder plug is plugged into the XS1 (socket). It is possible to install and connect in parallel several sockets for power tools operating alternately.

When the power tool button is pressed, the circuit closes and DA1 (phase regulator) is supplied with power. In this case, the capacitor C2 begins to charge, which leads to a smooth increase in voltage across it. The result of this is a delay in the opening of the thyristors (inside) of the regulator, and with them the triac VSI. The delay decreases in each half-cycle of the mains voltage, as a result of which the voltage flowing through the electric motor of the angle grinder increases smoothly and, consequently, its revolutions also gradually increase.

With the value of the capacitance of the capacitor C2, which is indicated in this diagram, a smooth increase in speed from the minimum amount to the nominal takes about 2 seconds, which is quite enough to protect the power tool from dynamic and thermal shock, and at the same time ensure comfortable work with the angle grinder.

After turning off the electric motor of the grinder, the capacitance C2 is discharged through the resistance R1 and after 3 seconds the soft start circuit of the grinder is ready for a new start. By replacing the constant resistance R1 with variables, it is possible to smoothly change the power supplied to the electric motor. The resistance R2 reduces the current flowing through the control electrode of the triac, and the capacitances C1 and SZ are the radio components of a typical circuit for connecting the KR1182PM1 microcircuit.
All resistances and capacitances are soldered directly to the terminals of the KR1182PM1 microcircuit.

It is possible to use any triac, with a maximum operating voltage of more than 400 V and with a maximum current of at least 25 amperes (depending on the power of the angle grinder). Due to the smooth start of the electric motor of the angle grinder, its starting current is not more than the rated current. The current margin is needed only in case of jamming of the power tool.
The soft start circuit has been tested with tools up to 2.2 kW. Since the KR1182PM1 chip guarantees the flow of current in the electrode circuit of the (control) triac VS1 during the entire active phase of the half-cycle, there are no restrictions on the minimum power of the connected load.