Smooth start grinders on the available parts
People who often use power tools sometimes face the following problem: the engine, whether it is a Bulgarian, a circular saw, a plane or other equipment, starts very abruptly. Such a sharp start is fraught with a lot of trouble: first, there is a high starting current, which does not have a good effect on wiring; secondly, the sudden start of the engine quickly wears out the mechanical parts of the tool; third, the usability is reduced; I have to hold tight, she tries to break out of her hands. The expensive models have a built-in soft start system that easily copes with all these troubles. But what if there is no such system? The way out is to assemble a soft start circuit yourself. In addition, it can be used with incandescent bulbs, because most often they burn out at the moment of switching on. The smooth start-up will significantly reduce the light bulb's ability to quickly burn out.
On the Internet, there is often a soft start circuit built on a rather rare domestic K1182PM1R microcircuit, which is not always easy to get. That is why I propose to build at least an effective circuit, the key element of which is the available chip TL072, instead you can also put LM358. The time for which the engine is gaining full revolutions is set by the capacitor C1. The larger its capacity, the more time it takes to overclock, the most optimal option is 2.2 μF. Capacitors C1 and C2 must be rated for at least 50 volts. Capacitor 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 circuit, you can use any low-power transistors, T1, T2, T4 have n-p-n structure, you can use BC457 or domestic KT3102, T4 has p-n-p structure, BC557 or KT3107 will fit in its place. T5 - any suitable for power and voltage semistrore, for example, BTA12 or TS-122.
Soft start making
The circuit is assembled on a printed circuit board with dimensions of 45 x 35 mm, the board is divorced as compact as possible so that it can be embedded inside the tool body, which requires a smooth start.It is better to solder the power wires directly to the board, but if the load power is small, you can install the terminal blocks, as I did. The payment is performed by the LUT method, the process photos are presented below.
It is desirable to tread the tracks before soldering parts, so to improve their conductivity. The microcircuit can be installed in the socket, then it can be removed from the board without any problems. First, resistors, diodes, small capacitors are sealed, and later the largest components. After completing the assembly of its board, it is imperative to check for correct installation, ring the tracks, wash the remaining flux.
First run and test
After the board is completely ready, you can check it for operability. First of all, you need to find a low-power light bulb for 5-10 watts and through it to include in the board a network of 220 volts. Those. the board and the light bulb are connected to the network in series, and the OUT output remains unconnected. If nothing is burned on the board, and the light is not lit, you can turn on the circuit directly to the network. The same low-power light bulb can be connected to the OUT output for testing. When connected, it should smoothly pick up the brightness to the maximum. If the circuit is working properly, you can connect more powerful appliances.With prolonged operation, the semistor may heat up slightly - there is nothing to worry about. In the presence of free space it does not hurt to install on the radiator.
On the board, during operation, there is dangerous mains voltage, therefore precautions must be taken. In no case should you touch the details of the board when it is connected to the network. Before switching on, make sure that the board is securely fastened and metal objects that could lead to a short circuit will not fall on it. For reliability it is recommended to fill the board with varnish or epoxy resin, then it will not be afraid even of moisture. Successful build!