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I'm building an Arduino-controlled Christmas light show. I power my 16-channel relay module with a 5V, 30A supply. It is placed outside the house and I want to place its power supply powering the relays inside.

I will have to run a wire from my workstation (where I set up my controlling PC and Arduino) outside to the spot where I placed my relay module (it needs a 10-12m long wire.)

I'm afraid that if I use an incorrect type of wire unsuitable to handle 5V, 30A, it would burn the wire.

Is there any thin wire that I could run for 10-12m carrying 5V, 30A power? Is there any type of wire that is thinner but still handles the power?

(Edited: I only need it to power the relay module, not the Christmas lights.)

ocrdu
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NF Squad
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    Why 30 amps? What are you powering that needs 30A and that needs relays? – bobflux Nov 22 '21 at 16:34
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    30 amps requires reasonably thick wire, there's no way around that. Using a higher voltage and lower current would allow thinner wire. – Hearth Nov 22 '21 at 16:40
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    Why 5V? With 30A, the loss is "great", considering 5V. Place a transformer near the Christmas lights, and send 48V... I = (5 x 30 x 1.5) / 48 ==> 5A. – jay Nov 22 '21 at 16:41
  • @bobflux, Hi! I'm building a Christmas lights controller using an Arduino to power a 16 channel electromagnetic relay module. I don't have enough options to choose from because I got my power supply from a broken pc. So I chose the one with the highest amp because the other options couldn't be able to power all simultaneously. I also need a longer wire to power the module. – NF Squad Nov 22 '21 at 16:42
  • It's just that I *highly* doubt anything is requiring 30A in that setup – Eugene Sh. Nov 22 '21 at 16:42
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    Do you actually need 30 amps at your load, or are you just looking at the 30 amp rating of the power supply and assuming that's the number you need to use? – Hearth Nov 22 '21 at 16:43
  • Looks like a duplicate of https://electronics.stackexchange.com/questions/34745/choosing-power-supply-how-to-get-the-voltage-and-current-ratings in disguise. – Eugene Sh. Nov 22 '21 at 16:44
  • I just want to add something about it, I'm not powering the Christmas lights themselves with the 30amp. I will only use it to power my relay module and it will control the lights by itself. – NF Squad Nov 22 '21 at 16:44
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    @jay Sounds like this is DC, so a little more complex than a transformer. I would just put multiple lights in series and run them off 48 volts directly. – Hearth Nov 22 '21 at 16:44
  • @NFSquad If you're using 30 amps for the *coil* of a relay, even several relays, you're doing something very wrong. That would only make sense in the context of huge industrial contactors, not tiny relays for christmas lights. – Hearth Nov 22 '21 at 16:47
  • @Hearth , I like that the most! Please post it as an answer... this and that... then "I suggest to do..." – jay Nov 22 '21 at 16:50
  • @jay It would be an answer if the question hadn't been amended to say that they only want to power the *relays* off of the 30 amp supply. In that case, there's no actual problem, since no sensible arrangement of relays for something like this would require more than one or two amps total, in which case any common lamp cord could be used. – Hearth Nov 22 '21 at 16:51
  • @Hearth, oh dud, less challenging.. :-) – jay Nov 22 '21 at 16:54
  • If this were 120 VAC power, then you would need 10 gauge cable for the 30 amps, per NEC guidelines. Even though this (since the voltage is lower) may not fall under electrical code regulations, the 10 gauge cable is a good starting point. – SteveSh Nov 22 '21 at 17:18
  • `I only need it to power the relay module, not the Christmas lights` if this power is only for the relays, you should not use a 30 Amp supply. I assume that the Christmas lights controlled by the relays are normal mains voltage? – Passerby Nov 22 '21 at 17:27
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    Use low-voltage outdoor lighting wire, available in any hardware store. Super durable, UV resistant. Way better than any "lamp cord" or other hookup wire you'll find – Kyle B Nov 22 '21 at 18:44

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If you're using the usual cheap "arduino relay module" it uses 70mA per relay, so 1.1A for 16 relays. So that's the current you'll actually need.

Basically any zipcord/lampcord/whatever wires around 1mm2 or more will do. I'd recommend using the usual "5V 2A" cellphone charger as a power supply. If you really want to use the 30A power supply, then you need to add a fuse on the 5V output so it doesn't melt the wires in case of a short.

That's assuming you're using the 30A power supply because you got it lying around but you're just powering the relay board with it.

bobflux
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  • Thanks for that! I'll try using the lower amp available from the power supply. Btw, I have a follow-up question, Is it okay to run 5v 2A power through a 10-12meters long zipcord wire? – NF Squad Nov 22 '21 at 16:55
  • @NFSquad Depends on the gauge of the wire. Is zipcord wire the same as lamp cord? – Hearth Nov 22 '21 at 16:57
  • Yeah zipcord is fine with 2A. The current through the wire will be only what the load uses (in your case the relays) so if all the relays are off it will be zero, don't mix up maximum power supply current with what your stuff will actually use. – bobflux Nov 22 '21 at 16:57
  • well "zipcord" is not tightly specified, but yeah, the usual 1-1.5mm2 lamp cord will work fine. – bobflux Nov 22 '21 at 16:58