This lm317 variable power supply can supply a voltages from 1.2V to 30V with a current 3 amperes, just as the title of this series based on LM317T voltage regulator, the LM317T regulator provide around 1.5 amperes on the heatsink, so by installing a parallel two or three of them will get a voltage source capable of providing 3 amperes. Obviously this also depends on the transformer used.
TheLM317T regulators are able to withstand short circuit at the output of the source and not so easily destroyed like LM350K or LM338K regulators, the regulator IC used in this circuit using ST manufacturing company and have shown positive result.
Note before assembling:
- Make sure the transformer is to provide currents as on the label.
- Regulators should be installed on aluminum heatsink very nicely.
- Although the source has a short-circuit protection and over-consumption, it depends on the size of the heatsink, because when this error occurs, the temperature emerges, and it is best not to give short for fun.
- When a short circuit occurs Power LED will be slightly decreased in brightness, but the best thing would have a voltmeter to display these errors.
Could someone propose a heatsink suitable for this supply. I have paralled two Radio Shack transformers which give me 12.5 and 25 v ac at 4 amps which could be used for input. I am looking for 20 vdc at 3.5 amps max for only one particular application. Other voltages and amps would only be frosting on the cake and nice to have. Thanks in advance
Wrong way to do it, see the data sheet for the right way.