Power supply [1.2 - 25V, LM317] ~ Electronic & Computer

Sunday, February 2, 2014

Power supply [1.2 - 25V, LM317]

2:03 PM 1 comment

After a quite a while, finally, I'm coming with new project. It's about simple power supply which anyone can make at home for really cheap price ($10) without transformer. It gives max 25V with 2A. Why can't give more than 2A? It's because LM317 can max handle 2A (TO-220 package), but i predicted that maybe it won't be enough so i made PCB board which can handle at least 5-8A of course without LM317. If i want more power, with output of 5A i can easily remove LM317 and replace 2N3055 (TO3 package) but then you need bigger cooler, but everything will working perfect. Also LM317 can handle up to 37V. That's not everything i assumed, also there is Volt,Amp meter integrated on board and stable +5V (LM7805) I'll show it below

Parts:

2 - Electrolytic capacitor - 2200uF/35V
4 - Block capacitor - 100nF
2 - Bridge rectifier - 2W10
1 - Green LED
1 - LM317
1 - LM7805
1 - Resistor - 1k5
1 - Potentiometer -10k
1 - Resistor - 460Ohm
4 - Terminal connector -1x2 (you can use them or you can solder wire direct to PCB)
2 - Header - 1x2 (Amp, Voltmeter again you can use them but you don't have to, It's up to you)

What you MUST consider before you make it

First some general knowledge, when you connect 120AC[US] or 230AC[EU] to appropriate transformer you will get 12, 15, 18, 24AC etc. on secondary, it's variable, depends of transformer. When you finish the rectification (AC to DC) you don't have 12, 15, 18, 24DC anymore. Actually you have the nominal secondary voltage multiplied with square root of 2. So it looks like 12*√2=17V, 15*√2=21V, 18*√2=25V, 24*√2=34V. Therefore you have to be aware of this, example: if you want 12V power supply and you have transformer with 12V AC on secondary, let's say you put 1000uF/16V Capacitor but your DC is 17V so when you connect this to city network, your capacitor is dead.

Second, YOU MUST BE CAREFUL when you working with 120AC or 230AC it can kill you instantly.

Schematic