Wire Amperage Rating?

[Falcon69]

Okay, so I have like 1500ft of 26 conductor 28AWG stranded ribbon cable.

I have a project that will see a total amount of about 375mA at no more than 5.2volts.

Would it be okay to use this wire for board to board connection.  Each Ribbon cable would be cut to 18 inches with necessary connectors (IDC) on the ends to connect to the boards.

I'm a bit confused by what this site says: http://www.powerstream.com/Wire_Size.htm

It says for chassis wiring 28AWG is good for 1.4A and power transmission of 226mA.  What's the difference between those two? Also, are they rating that at 1000ft?

Thanks in Advance!

[Falcon69]

Hmm,

Wiki says 830mA in enclosed air, 1.4A in free air.

The wire I have is Belden 105c 300v http://www.belden.com/techdatas/english/9L28026.pdf

That chart shows 1A max at 20 celsius.  That seems alot for such a small wire.  SO, based on that, I should be okay then?

[Rufus]

It says for chassis wiring 28AWG is good for 1.4A and power transmission of 226mA.  What's the difference between those two?

They are talking about acceptable dissipation in the wire regardless of length. What is considered acceptable varies widely with application and is pretty arbitrary anyway.

The more important issue for wires of significant length is voltage drop. Try this http://www.rapidtables.com/calc/wire/voltage-drop-calculator.htm

[Falcon69]

Awesome, thank you Rufus.  I'm bookmarking that page.

at 375mA, 5.2v, 18inches, the voltage drop is only 0.0728v.

I can work with that.

[Paul Moir]

There's nothing wrong with using a pair or more wires to lower your voltage drop if you have some to spare.

[Falcon69]

I thought about that Paul.  I have 1 extra pin on the connector.  I would need two, one for power, one for ground to double up on the amp rating of wire, correct? So 2 and 2?  If that's the case, it won't work, but, I think the wire should be fine. If it's rated for 1A at 20 celsius or 830mA continuous like Wiki says, should be okay.  I'm at a max of 375mA through it. (not all the time mind you)

[Paul Moir]

No prob.

You can use three and get 3/4 the voltage drop.  If you double up the grounds, half the voltage drop will be on the supply and you'll get half of that half returning on the ground.  (PS it looks like that calculator does "round trip" voltage drops, so the return has been accounted for in it.  Check for yourself if you're worried.)

I would be very surprised if you had any trouble at .375A on a single conductor.  1A would be pushing your luck.

[Falcon69]

sounds good.  I will stay with the 28awg then.  Thanks

[jesperscott]

The more important issue for wires of significant length is voltage drop i used this calculator http://www.calculatorology.com/voltage-drop-calculator/ at 375mA, 5.2v, 18inches, the voltage drop is only 0.0728v.