Hello, I bought 2 relays and usually you select the voltage before buying (5V, 12V or 24V) but for this one it's indicated between 5V and 30V.
The first one is connected to 9V and still working fine.
The second one burned quiclky on 12V.
Can you confirm this relay works between 5V and 30V or only 5V? In this case why the second didn't burn? Otherwise the problem could be a defective relay or my 12V adapter not good.
Thanks
The photo is small, but looks like 5V operation to me. There will be a tolerance on this , of course, for that you will need to search for the data sheet. If it is a 5V operating relay then 30 V is 6 x the voltage so 36 x the power will be dissipated in the coil. Very likely to burn it out.
In changed by a bigger photo and yes, it is writtend 5VDC it's why I don't undersand the description of the product which seems not correct 
So, the second one, now I wonder how long it will work at 9V !
Coil voltage is 5V, so you're likely reducing the life of the one you're running at 9V.
The other numbers on the relay are telling you how much power you can run through the NC NO and common connections on the other side of the relay.
For NC NO COM it could be 250VAC or 30VDC as I can read
Indeed, but it seems to be the 10A value that really matters, although I suspect that's aspirational. Those relays aren't known for their longevity - take the fried one apart and look at how small the relay contacts are.
Ok, thanks for your help!
It is not safe to run a relay on almost 2 times the rated voltage. It will dissipate almost 4 times more heat than it was designed for. It may emit toxic gasses, catch fire...
It is a 5VDC coil, I think everything else is related to the contacts.
Yes ,the 30V spec is in regard to the contact rating. On AC voltage the power passes through zero to extinguish the switching arc. In a DC setting the arc is maintained longer hence the lower voltage number.
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