I'm a mechanical engineer who's recently gotten into electronics, and I'm a tad stuck with this new design I'm working on.
The idea is to have two separate batteries powering two separate lines, but if one battery were to cut out, the other would take up the supply of both loads. (Table in image with L A and L B being loads A, B).
The circuit I have now is using depletion MOSFETS for their normally open mode of operation. I've been having trouble finding good info on depletion MOSFETS, and have a feeling that my circuit isn't quite right. The resistors might not have to be there, and may actually have to pull to ground, but again, my understanding of depletion MOSFETS is shaky.
The idea behind the circuit is that when the battery is active (let's say B2), it turns off the normally open MOSFET, and supplies it's own power to load B. But if B1 is off, Q1 is open, so power can flow from B2 to Load A.
Another question I had was with grounding this circuit, I should just tie both negative terminals together, as well as the load lines's ground right?
Nominal conditions are 2S lipos or 9V batteries for power, with nominal loads of 200 ma, with possible 1-4 A spikes for ~ 2-20 ms every now and then (9V batteries themselves are able to handle those spikes very well).
Current parts are: MOSFET - Digikey Diode - 1N5817-TP
(MOSFET very subject to change, just one that I found in a TO-220 package with ~1A current capacity (800ma)).
Any help would be appreciated, Thanks