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Automotive relay
mgb:
Good point on the ac or dc switching. But it really comes down to what the contacts are rated for and these appear to rated for 30A, assumably with 12 volt. The 12 or 24 volt mentioned are just what the coil takes.
I was under the impression he will be switching 12 volt dc for the amp power.
Mysterioii:
I believe some (most? all?) solid state relays only conduct in one direction, in which case AC might come out half-wave rectified... You are justified in your concern that there might be additional damage if the relay burns out though... I had a relay on the controller board for my upstairs furnace/air conditioner burn out last year when it couldn't cool the second floor enough and basically ran all the time. It scorched about an inch radius all around the relay and burnt a small hole through the circuit board including burning some traces. Replacing the relay wasn't an option at that point and I had to buy a replacement board online for $130 (which would have cost me more if I got it through an AC guy and paid him to put it in). However, any electronics COULD burn if a failure happens so just be careful and position things away from flammable materials, use standoffs, etc.
kwijibo007:
I have a power brick that I scavenged from an old modem/router. It takes 240v in (I'm from Australia) and 12v DC out.
The power brick is always powered, even if the PC is off, as it also powers a small garage door opener circuit board that I bought of the net for $20. The garage door opener circuit board has a remote (the type you use to unlock your car). The remote has four buttons which correspond to four built in relays (nothing to do with the relay in question) on the board. I use one button to power on the PC and one to add Mame credits. I have a coin mech and internal power button also... It's just that access to the pysical power button is reached when unlocking the coin mech door. The idea was so that I can power on the PC without unlocking the door and I can add credits without inserting a coin.
The DIY relay is attached on the 12v DC side of the power brick. Is the relay ok given mgb's diode advice? Or should I re-think?
mgb:
Why not give it a shot, the worst thing that would more than likely happen is the relay burns out. This doesn't mean it catches fire, it just ceases to work.
I will say however though that the relay you got is not really rated for continuous duty but for extended duty. I thinks its more for air horns and that kinda thing but again the worst thing is that relay may die and if that happens just swap it with something hardier.
Mysterioii:
--- Quote from: mgb on August 20, 2012, 11:16:52 pm ---Why not give it a shot, the worst thing that would more than likely happen is the relay burns out. This doesn't mean it catches fire, it just ceases to work.
--- End quote ---
Well, some times they catch fire. I could show you a furnace control board where it did. I've seen it happen elsewhere. Happens sometimes, just think things through and don't put them behind the curtains. I agree though, it is more likely that they will simply be stuck off or stuck on.
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