I2C switch / output expander with Open Drain

.... another thought. In this set-up, would it make sense to not use the open collector P0 of the extender (there's only one - we may have a better use for it later) and use one of the push-pulls?

btw, just simply leaving it disconnected will allow the system to work, it won't drive the output on if either of the other two connections are still low

It was not transients in my little mishap, it was a gross overloading of the FET that then cause the shunt resistor to fail (A rather expensive one I might add ) and consiquently feeding the source voltage right into the OPAMP inputs, grossly exceeding their input protection limits.

, its great to win a contest and upgrade your lab, then sell the old stuff to add even more coolness to the bench

You definitely deserved to win that one btw...

I sold my previous soldering station last week - a decent one but a few steps down from the one I won (it was also several steps down in $$).

The great thing is that both me as the seller and the person who bought it were delighted with the deal. And it gets me some budget to throw towards the DC load.

Yes, use one of the push-pull outputs.

OK, understood. But the question was do you need Jan to add anything for protection purposes that can't be dealt with just by the processor shutting the MOSFET down? If not, Jan can have a go at a first draft of the board.

Jon Clift wrote:

...

 

Love that PSU. Why aren't you using it?

Also: this was the first supply that I had that was able to run in constant current mode. The other ones I had either blew a fuse or (the self-modded one based on an Oppermann kit in 1982 or 3? and my first commercial supply) switch off at over current.

I like the maximum current future more than the ones that just switch off. Even worse, I have a commercial one that goes to -0.7 V when current exceeds the set point. That's Not Funny.

I dont think anything more than we already have, all the op-amps have suitably high resistors to protect them and a diode off board should be across the sense resistor, maybe two could be there (Back to back), the FET already has one and as already suggested, a fuse should also help. we just dont want too much in the power path in order to still handle high currents with low voltage