Smooth start of the grinder on accessible parts
People who often use power tools sometimes have the following problem: the engine, be it a grinder, a circular saw, a planer 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 the best effect on the wiring, secondly, a sharp start of the engine quickly wears out the mechanical parts of the tool, thirdly, ease of use decreases; 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.Smooth start will significantly reduce the ability of the bulb to quickly burn out.The Internet often meets a soft start circuit, built on a fairly rare domestic chip K1182PM1R, which it is not always easy to get now. That's why I propose to the assembly no less effective scheme, the key element of which is the available TL072 chip, instead of it it is also possible to put LM358. The time for which the engine is gaining full revolutions is set by the capacitor C1. The larger its capacity, the longer it will take to accelerate, the best option is 2.2 microfarads. 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, any low-power transistors can be used, T1, T2, T4 have an n-p-n structure, BC457 or domestic KT3102 can be used, T4 has a p-n-p structure, BC557 or KT3107. T5 - any suitable for the power and voltage of the sevenistor, for example, BTA12 or TC-122. "
Making a soft startThe circuit is assembled on a printed circuit board with dimensions of 45 x 35 mm, the board is as compact as possible to its could 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 fee is carried out using the LUT method, photographs of the process are presented below. Download fee: It is desirable to zip the tracks before soldering the parts, so 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 start-up and testingAfter the board is fully prepared, 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 continued operation, the seven-watt may be slightly heated - this is okay. In the presence of free space it does not hurt to install on the radiator. There is dangerous mains voltage on the board during operation, so 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, then even moisture will not be afraid of it. Successful build!
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