I'm trying to translate a circuit I made from breadboard to PCB and need some help finding out what components I should be looking for.
Basically, so far I have a very simple circuit running 12V AC, at about 10-20A using a relay.
I'm controlling this relay with an arduino, so if I give 0v the circuit flows towards circuit A, and if I give 5v, the relay switches the flow to circuit B.
My issue is that the relay is too big for my application, I need something smaller, that I can fit in to a smaller chip.
From my research FET's is what I should be using, but are there other easier components I can use? With FET's, I will need to use an optocoupler to drive them from the arduino correct? Are there simpler ways?
Best Answer
SOME FETS around that size are usable.
You will need two in series with opposed polarity for AC.
Join Gates.
Join Sources.
Two Drains are an AC switch terminals.
Drive gate to source with floating voltage (details if needed).
BUT with say 5 milliOhm FETS your dissipation is
I^2 x R = 20 x 20 x 5/1000 = 2 Watts per FET.
With 1 milliOhm FETS that's 0.4 Watts/ FET. 1 mO FET is "special but doable".
Careful design and heatsinking needed.
What are your size constraints and why?
Slightly larger. Just.
5mm x 6mm x 1mm.
30V 100A+.
Under 1 milliOhm so eg say ~ 0.5W at 20A.
In stock Digikey $1.98/1 http://www.digikey.com/product-detail/en/PSMN0R9-30YLDX/568-11554-1-ND/4965575
Datasheet here
Heatsink well enough and they will work well.
Need not be "large" but must be adequate.
Larger version ofdiagram here
Added:
I just found this earlier SA Q&A
What transistor or combination of transistors should I use to make a fully controllable AC switch?
Diagram below from Andy's answer matches what I described above.
Isolated gate drive need not actually be truly isolated - ask.