My project uses a 1.5V glowplug, which draws quite some amps to get as hot as it needs to be. I don't know how much, but the RC plane guys told me they often use a special battery (3300 mAh) to provide the amps. They need need to keep it going for quite a while, me a few seconds. I'm wondering how to decide what to use, a relay, a mosfet or an optocoupler. I'm not a hardware guy, and they all seem very similar to me. I understand that a relay can handle about any kind of current, where a mosfet is more limited, but what is more? Also the mosfet examples I see all use the same power source, whereas I'll use a separate power source for the Neo and the glowplug. Then again there is also the OptoCoupler, which is nice small instead of the big relay. What would be the limitations of this? And as the Neo provides 3.3v I see a lot of relays (all?) requiring 5v. The relay I tried did indeed not work on the Neo, but did on a Uno.
Forget the opto, unless you add more circuitry. It won't handle the current by itself. At 3 Amps, the MOSFET is a good candidate. The relay will need driver and protection circuitry(transistor driver, and a protection diode). There is also the "solid state relay" which you didn't mention. Probably more expensive, but easy to interface! I'm an electronics technician by profession...
Thanks for the info. I'll check out the mosfet. A solid state relay seems quite some overkill, if I look at the device. I need my glow plug to be heated for a short time. In my current experiments a standard AA battery did the trick.
