[Deetman]

Originally Posted by techhelpbb

That's about right. You shouldn't need the transistors at all.
I wanted to make sure to lower the coupling ratio...so I used the minimum.

I have the surface mount and the through hole version of the PS2501-4 and basically all the surface mount version is, is just the leads bent parallel to the surface, so no real weight savings.

The schematic I was working on had an extra trick, in that it was designed so you could test the circuit end to end without any tools. Figured we had enough people nervous about going this route that making it 'self test' was a the best solution to calm the nerves.

Thanks for the taking the time to review the schematic. Second sets of eyes never hurt.

I'll take a look again at the diode current. I didn't consider the coupling ratio since I haven't really used opto-isolators before.

I noticed that too about the surface mount version of the PS2501-4 which surprised me. Other than automated manufacturing the benefits of going with the surface mount version are pretty small.

Also a great concept on the self test circuitry... I didn't really think of doing that since theoretically this has already been "proven" to work. I'll probably take the board into work once I get it and run a pulse generator on it to test the board.