16 volts too much for 12-volt relays?

[Hogarth]

Hi chaps. I've got some 12v relays in my control panel and I'm powering them with an old 12v DC adapter. At least, that's what it says it is, but I'm getting a reading of 16V across the terminals when the relay is switched on. Is this going to knacker the relay coil. If so, how can I get the voltage down? Cheers!

[lord groan]

1st thing I'd do is check the manufacturers specs for the relays, they've often got a voltage range they'll work at and 16v may well be within range. If they do need 12v then I'd deinitely stop using that dodgy adaptor, I suspect adjusting the voltage will be practically impossible. For my 'tiny brewshed' build I needed 12v for the steam extraction fans and for the IC water pump. My solution was an old pc power supply, they provide a very accurate 12v with a high current capability, mind you they come with way too many wires. For mine I opened the case and very carefully cut off all the surplus wires just leaving one 12v and one ground, insulation tape around the cut ends and closed up the case. Result = a rock steady 12v with lots of amps available to drive all sorts of things. BTW you also need to find the wire that the pc power button connects to and short that straight to earth (the purple one in the big connector iirc but google it to make sure won't you) so that it swiches on whenever you connect the mains
BEWARE If you open the case on one of these be very careful, the big capacitors store 240v for some time after switching off and unplugging. If your finger touches the terminals it has enough ooomph to vaporise a small hole in your finger, voice of experience here!

[themadhippy]

sounds like your using an unregulated psu, quick n dirty method would be an extra bit of load ,for example 12v 5w lamp,or a resistor either as a load or in series to drop the voltage ,more expensive and slightly over kill would be a 7812 voltage regulator.

[Hogarth]

1st thing I'd do is check the manufacturers specs for the relays

Ah, good call. They're rated at 9.6 - 13.2 volts, so I guess 16v is overdoing it.

,more expensive and slightly over kill would be a 7812 voltage regulator.

Thanks, Hippy. Could I use a voltage regulator like this? As well as a couple of relays I'll also be driving a brushless computer fan if that makes a difference.

[themadhippy]

Maybe,all depends on what the voltage drops too when youve everything running.

[BenB]

Or just use some inline diodes to drop the voltage - only the + wire needs cutting then.

[Hogarth]

Thanks guys. I'll give the voltage regulator a pop — it's only £2.99.

[Hogarth]

That seems to have done the trick.



Thanks Hippy. Now I just have to find a way to fix it.