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Thread: stupid relay question please help

  1. #1
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    stupid relay question please help

    ok ive searched all over for this answer and i think i already know it but i just wanna make sure. everyone knows that when you connect the positive lead of a battery to the negative or ground it shorts the battery and that's bad. well when using a relay, if you run a wire from the + terminal to the coil of the relay, and then just ground it doesn't that short it out? in every post ive seen this is what people do. it just seems to me this would short out the battery unless the relay coil had some sort of resistance or votage usage. will someone please explain this to me. any help is appreciated. thanks.

  2. #2
    Variable Bitrate numbers's Avatar
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    The relay coil does have resistance. Look at the specs for your relay and it will say that is uses something like 50ma at 12v.

  3. #3
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    so you can run it straight out of the battery and right back in without worrying about shorting it?

    here are the specs for the one i am using. http://support.radioshack.com/suppor...oc38/38002.htm

  4. #4
    Variable Bitrate numbers's Avatar
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    Yeah you can.

  5. #5
    Newbie Cocoman's Avatar
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    By that logic even light bulbs would cause short circuits since they are also coils and involve connecting +ve to -ve. Obviously this is not a problem because they do not blow fuses in your house everytime they are turned on. As numbers mentioned, it does have some resistance so its not the same as hooking up the the +ve lead to the -ve lead directly.

  6. #6
    Variable Bitrate 84RegalRider's Avatar
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    be careful though. Make sure you run the wires to the coil and not the Normally Closed contacts, or you will see sparks fly. But a fuse inline just in case like always

  7. #7
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    where should i put the fuse? before the coil or before the switching side?

  8. #8
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    Bugbyte's Avatar
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    Put it between the +12 and the coil. Before the coil.
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