Lab power supply with PIC microcontroller (4)
November 9, 2013
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I made some small changes to the schematic. I added a zener to protect the voltage feedback into Vloop opamp.
Also I changed the way the current limitation loop take over the voltage loop. Previously I was thinking to lower the REF voltage when the ILIM is reached. I think a better way is to use 2wo diodes ( 1N4148) and a 5K resistor to make a OR function. This works better and the transition is smooth. I was looking also at similar power supply from big brands ( Agilent, HP) and they do the same thing.
The new version is 3.1:
I made also an experiment to see hot the etching process works and how good are the tracks. I am disappointed somehow since I did not used a toner transfer but a simple permanent marker. The copper was partially etched on the areas where the marker was thin only. Where it was thick it is ok. To etch I used hydrochloric acid (HCL 25%) and oxygenated water (H2O2 10%)
I didn’t had access to a laser printer but I hope so make a full size experiment soon with toner on the real PCB.