Simple adjustable power supply
When you collect any electronic home-made, then you need a power supply to check it. There is a wide variety of ready-made solutions on the market. Beautifully decorated, have many features. Also a lot of kit-kits for self-production. I'm not talking about the Chinese with their trading platforms. I bought on Aliekspress board modules down-converter, here on it and decided to do. The voltage is regulated, there is enough current. The unit basically has a module from China, as well as the radio components that I had in my workshop (they had been waiting for their time for a long time). It regulates the unit from 1.5 volts to the maximum (it all depends on the rectifier used up to the adjustment board).
Description of components
I have a 17.9 Volt transformer and a current of 1.7 Ampere. It is installed in the case, it means it is not necessary to select the latter. The winding is quite thick, I think, and 2 Ampere will pull. Instead of a transformer, you can use a pulsed power supply unit for a laptop, but then you also need a case for the other components.
The rectifier of alternating current, there will be a diode bridge, can be assembled from four diodes. Smooth pulsations will be an electrolytic capacitor, I have 2200 microfarads and a working voltage of 35 volts. Used second-hand, was in stock.
Adjust the output voltage will be the Chinese module. There are a lot of them on the market. It provides good stabilization and is quite reliable.
For a comfortable adjustment of the output voltage I will use a 4.7 kΩ adjustment resistor. The board has 10 kΩ installed, but I have what I put it on. The resistor is still the beginning of the 90s. With this rating, the adjustment is provided smoothly. I also picked up a pen on him, also shaggy.
The output voltage indicator is a voltmeter from China. He has three wires. Two wires are powered by a voltmeter (red and black), and the third (blue) is measuring. You can combine red and blue together. Then the voltmeter will be powered from the output voltage of the unit, that is, the indication from 4 volts will light up. Agree not convenient, so I will feed it separately, more on that later.
To power a voltmeter, I will apply a domestic microcircuit of a voltage regulator for 12 volts.This will ensure that the indicator-voltmeter works from a minimum. The voltmeter is powered by a red plus and black minus. The measurement is carried out through the black minus and blue plus the output of the block.
My terminals are domestic. They have openings for banana plugs and openings for clamping wires. Similar can be bought in China. Also picked up the wires with lugs.
Power supply assembly
Everything is going on a simple sketched pattern.
The diode bridge must be soldered to the transformer. I arched it for a comfortable installation. The condenser was soldered to the output of the bridge. It turned out not to go beyond the height.
The power supply to the voltmeter was screwed to the transformer. In principle, it is not heated, and so it stands in its place and does not bother anyone.
On the regulator board, a resistor was dropped and two wires were soldered under the external resistor. Also soldered wires to the output terminals.
On the case marking the holes for everything that will be on the front panel. Cut out the holes for the voltmeter and one terminal. The resistor and the second terminal set at the junction box. When assembling the box, everything is fixed by squeezing both halves.
The terminal and the voltmeter are installed.
So it turned out to install a second terminal and an adjusting resistor. A resistor made a cut-out under the key.
Cut the window under the switch. The body is assembled and closed. It remains only to unsolder the switch and the regulated power supply is ready for use.
The power supply adjusts the voltage from 1.23 Volts.
The maximum voltage is 19 volts.
Displays the voltmeter fairly accurately. 20-30 millivolts do not consider such a strong deviation.
I connected a motor. Voltage does not sag.
This power supply is simple and does not display the load current. Maybe this is a minus, but this case would not accommodate another ammeter and current adjustment is not provided. So I coped with the task.