Hello guys! I stumbled upon Peter Oakes' DIY PSU on element14's website and eventually on his YouTube channel. I thought this would be a good project to work on as it's a nice opportunity to learn how stuff works hands on. I watched all the video series and I'm confident I can get something along those lines working. Checked my parts bin and found a couple of op-amps and the other passives required to build the PSU. Before going all-in and etching/ordering a PCB, I decided to test on the breadboard what I had. Here is my version:
Then the suggested basic psu
and then the final iteration of the psu.
I have deviated a bit from the suggested layout by:
- using no differential measurement (using a 1R sense resistor) as I don't have a precision op-amp.
- not using a voltage reference: I have a couple of TL431s around and can replace them to the I&V-set pots.
Otherwise:
- the zener diode is a 6V zener
- V+ is filtered DC input, for now from a power brick but later I will be using a 24V transformer.
- I'm aiming for 0-3A and 0-15V ( eventually 0-24V) on the output
- precision is not my topmost priority. This is going to be a proof of concept and if it works, V2..etc will aim for precision and/or accuracy and also possibly digital control.
So now I have everything on the breadboard but if I float the "analogue" ground on the V_OUT rail, it just doesn't work: zero volts on output, zero milliamps. But when I do join both "analogue" and V_RAW ground, the circuit works as intended but the current goes only to about 4mV on the output even if I turn the pots all the way down.
Now I actually don't know why the "analogue" ground floated doesn't work but with common ground all works. Any hints or gotchas (a.ka. traps for the young players
) I missed?
p.s. The images Basic+PSU.png and PSU+MkII+RPO+fixed.png are all properties of Peter Oakes hosted on element14.com.