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• posted on August 24, 2008, 4:24 pm

I soldered everything together like in the picture. The relay works as it should but having it on it gets really hot. What could be wrong? I can't think of anything but a short circuit since the copper wire is seems to be the culprit.

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• posted on August 24, 2008, 9:32 pm
John Smith wrote:

Hot is okay. Melt is bad.
If the latter, use bigger wire.

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• posted on August 24, 2008, 10:12 pm
wrote:

Also remember that things like motors -both ac and dc - are basic coils of wire, also transformers - ac- are just two coils of wire next to each other.( Most have an iron core between them to help the magnetic lines of flux I think, it's been a long time here also !!!)

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• posted on August 24, 2008, 10:41 pm
On Sun, 24 Aug 2008 17:12:37 -0500, "Mark H" <nomail> wrote:
[snip]

BTW, there's no such thing as a DC transformer. Only a changing magnetic field (as from a changing current, AC) will generate current in the secondary. Consider that if a transformer could work on DC, you could substitute a permanent magnet for the core (and eliminate the primary). You would now be getting something secondary current) for nothing, an obvious impossibility.

An iron core is used at normal power supply frequencies. It's made of multiple thin layers shaped like the letters E and I.
--
Mark Lloyd
http://notstupid.laughingsquid.com

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• posted on August 24, 2008, 11:09 pm

Almost all wire is copper. Plus I think you're misunderstanding short circuit. A short circuit is one in which some part of the circuit, usually the load, is bypassed completely or partially.
Plainly your relay (the load) isn't being bypassed completely, because if it were, it wouldn't be hot.
Do you think there is a short circuit between windings inside the relay coil? That's rare, and it takes some abuse of the coil to make it happen. Was this a new relay, one from surplus (working correctly when it goes out of use), or one from junk which wasn't working right when it went out of use? If the relay was good when you go it and you haven't used substantially more voltage than it's rated for, the odds are very high its still good.
I think it's time you told us more about the device. What are you using for both sources of power? What are you trying to control with the relay? What determines if the relay closes or not?

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• posted on August 25, 2008, 2:44 am
wrote:

Since it is relatively fine the wire in the relay has quite a bit of resistance and thus does not make a "short circuit". If the relay is actually overheating then either the voltage is too high or else you have an AC relay and your "transformer" puts out DC because it includes a rectifier. Your "transformer" might also put out more voltage than it says because it is intended for a higher current load. In other words, your relay and power source are not compatible. You probably could add a resistor in your circuit to solve the problem but you have not given enough information to calculate its value. If you post the information on the relay and the "transformer" someone could help more.
Don Young

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• posted on August 25, 2008, 4:29 pm

Almost too hot to touch is too hot; means the voltage to it is wrong. Coil windings lifetime will be shortened considerable and it could become a fire hazard as the coil wire coatings begin to melt and short out. Wrong voltage.