Simple 12V DC power supply
Do you want to build in instant a simple, cheap and efficient 12V DC power supply? Then this project is perfect for you! ;) The whole setup contains:
- main toroidal transformer, AC voltage output 19V, several tens of watts
- rectify bridge or four diodes connected in Graetz bridge
- LM7812 voltage regulator (datasheet)
- 10 000µF 35V electrolytic capacitor (although it doesn't have to have such big capacitance, 2200µF is enough)
How it does work? Main transformer converts 230V AC from mains to lower voltage AC 19V. Next current is rectified by rectify bridge and thanks to that, current becomes a DC with voltage equaled to input voltage multiplied by squ. Then, current is smoothed by capacitor and voltage is lowered by LM7812 voltage regulator. Keep in mind that voltage drop which occurs in regulator, causes additional dissipated heat. Furthermore, regulator has, according to datasheet, own voltage drops to amount to 2V and it's independented of input voltage. To estimate heat value, you have to multiply total voltage drop (it's enough to measure Input and Output with voltmeter) with current flowing through regulator. So, the lower voltage drop is, or bigger heatsink, the better. The most reasonable option would be using main transformer with AC output 9V (after rectifing, it would be 13V and voltage drop equals to humbly 1V). Between ground a regulator's output we have DC 12V. Now, it's about time for photos:
Transformer:
Soldered and ready:
