I found the current limiting circuit on the web, I'am powering this circuit from a 12V 20A switching lab power supply. The problem that i have is that current regulation doesn't work, voltage regulation works fine. but when i adjust the current (above 1 amp usually) the circuit completly shuts down. the 2n3055 transistors are a bit warm but that should not matter since i only wanna test if it's capable of 2 - 3 amps for maybe 2 seconds. But the circuit just dies.
If i leave it like that (dead) but still plugged in, it comes back on again after maybe 10 seconds, then shuts down again etc.
My first thought is that the LM317 overcurrent protection is kicking in, but since the transistor is taking most of the load that shouldn't matter right?
The LM317 is very cold btw. Not hot at all. My guess is that i simply forgot to add something but i can't figure out what..
I don't have any capacitors in this circuit on the breadboard, could that be the cause of the problem?
Thanks for any help in advance!
LM317 datasheet: http://www.ti.com/lit/ds/symlink/lm317.pdf
2N3055 datasheet: http://www.onsemi.com/pub_link/Collateral/2N3055-D.PDF
Update: I just noticed that current changes when i put a finger on the current regulation pot.. if it shows like 300 mA and i put my finger on it, it goes down to maybe 150 mA and jumps around until i remove the finger.. (Tried to change the pot but same problem occured)