Hello everyone,
I need to build a small 3 rail PSU with the following requirements:
24V @ ~ 100mA (OpAmps supply)
12V @ ~ 200mA (2x Cooling fans)
5V @ ~ 500mA (Logic and other circuitry).
I have a transformer 15-0-15 transformer that can be wired either in serie or in parallel. I have a feeling that if I power up the attached design, magic smoke will show up, if not worse. My concern, here, is the grounds are not tied to the same point on the transformer. Is my first impression correct?
I could drive the 7812 from the 7824, but it will quadruple the heat dissipation from ~2.1W to ~8.4W. I want to avoid using a switch mode regulator to avoid noise on the opamps because I need as much precision as possible out of those. Any suggestion for improvements?
Many thanks
EDIT:
Filter caps were intentionally left out for clarity. -- Thanks MosherIV for pointing that out.
The OpAmps inputs are fed with a 0-20V signal. I'm not sure how to deal with it if I use a split ±12V supply, as many have suggested. The OpAmps are LM324 and unless I missed something in the datasheet, the input cannot exceed the power rails. Ideally, no current should be drawn from the input signal, although I can live with a few microamps.