good wire capacity chart?

[gadget-evilusions]

Does anyone have a good chart for allowable loads thru specific gauge wire. Mostly I just want to see the max current at 12vdc for 24, 22, and 18 gauge stranded wire.

[JonnyMac]

Are you looking for max current, or for voltage loss?  You can find voltage loss charts from every vendor that makes wire.

Here's a discussion on calculating volatge loss:
-- http://www.paigewire.com/volt_loss_formulas.htm

And here's a handy calculator that will tell you the wire resistance (plug into Ohm's Law, E = IR):
-- http://www.cirris.com/testing/resistance/wire.html

You don't want to drop more than 5% through the run of wire.  And keep in mind that if your valve is 10 feet from the controller, you actually have 20 feet of wire to calculate the loss for.

Using the resistance calculator you will find that 20 feet of #24 wire has a resistance of 0.513 Ohms.  If you're running a valve that operates at 0.25A then the voltage drop through the wire is:

  E = IR
  E = 0.25 x 0.513
  E = 0.128v

0.128v / 12v = ~1%, so this would be safe -- so long as the wire was mechanically strong enough to handle what you're doing with it.

My rule with wire is the same as with guns on a battlefield: bigger is almost always better!

[gadget-evilusions]

I am calculating for power wire to led arrays. According to those calculators I only have .257 voltage drop over 10' of 24ga wire. I think that is acceptable.

I am looking for max amperage/wattage also. The led lights I am building (and controlled by a prop-1) are going to have 24 ga wire, and I wanted to make sure the wire would safely handle what the ULN can pass if I were to load up one channel in a worse case scenario.

[JonnyMac]

I just posted an update to my original response using 0.25A in the calculations -- this is what the ULN can safely handle when multiple outputs are active.

I just found this chart (Google is my friend):
-- http://www.powerstream.com/Wire_Size.htm

It shows that #24 wire can handle up to 0.577 amps -- I think you're safe, but just barely.  The ULN max current for one output on is 0.5A.

[gadget-evilusions]

Thanks. I have been looking for good info, but up until this point, all of it has differed and I wasn't sure what to trust. Thanks.