I’m thinking of getting a cheap-o relay module from China but thought I’d ask if that’s what I need.
I have an Arduino that runs on 3.3V and I want it to turn on/activate a circuit that’s running at ~12VDC (3 cell Lipo). Can I use the relay modules for that? They are pretty short on documentation 
example: http://www.aliexpress.com/item/Free-Shi … 31471.html
In the feedback section, one fellow says:
Product as described, works with 3,3v. Fast delivery. Would recommend
another says:
Product works ok, but it doesn’t work with 3 volt version arduino
Sorry, it wasn’t the 5V vs 3.3V that I was asking about. It is the 12VDC vs 120VAC. Every single example I’ve come across is about switching on household appliances. I couldn’t find anything about turning on a battery-powered device.
But I’ve since figured it should be OK and that’s what the 28VDC/30VDC markings are about. But I am still confused why it says 240VAC and 30VDC on one side and 120VAC and 28VDC on the other. If that’s an “input” and “output” then the 5V makes no sense. Or does that mean somewhere beween 5V and 28V DC or between 5V and 120V AC to switch it?
For 3.3V being too low… I’m sure I can get that up to 5V if necessary.
My experience with relays says that those ratings are all 10 amp @ any of the voltages specified: 28 or 30VDC or 125 or 250 VAC. Not related to input. Just contact ratings.
The part number has the 5VDC coil voltage in it : SRD-05VDC-SL-C.
you will likely be fine.