For the new tinker system I started on I wanted to add a small bench power supply that is variable from 0 to 12 volts. Since the power supply is mostly intended to power up sensors and modules for Arduino shields and Raspberry Pi hats I slapped together a small supply. I wanted to use a LM317 but I got a ton of LM7812s laying around so I came up with this.
Basically it’s a bunch of junk parts I have laying around. The LM7812 is more of a reference voltage and the LM358 and both BC537s in a Darlington array is doing the work. I might switch out the BC537s for a 2n3055. I still need to add a couple of options such as a power light indicator and a output relay so I can turn the output on and off. Maybe I could get rid of the pot and drive the thing via PWM and control it with the Pi.