How much AWG do I need for my circuit wires knowing that the current can vary 10 to 20A with 12V supply
And what is the cheapest and safest way to join 2 wires together ?
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1This took about 1 second to google, http://circuitcalculator.com/wordpress/2007/09/20/wire-parameter-calculator/ . I set the wire gauge to 12 AWG and it showed 23 Amp current handling. Usually these are calculated to give 10 Degree Celsius rise in temp from ambient ( i had that set to 25 degrees Celsius) – KyranF Oct 12 '14 at 11:02
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as for joining wires, using a screw socket terminal strip is pretty good! Maybe some shrink wrap to keep contacts from touching – KyranF Oct 12 '14 at 11:02
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- it depends on the length of the wire, the voltage drop you can tolerate, and the temperature you can stand.
– EM Fields Oct 12 '14 at 11:11 -
AWG rating Relates to current http://www.powerstream.com/Wire_Size.htm – Sanjeev Kumar Oct 12 '14 at 11:18
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EM Fields is right about the voltage drop, be careful about the estimated cable resistance and use Ohms law with the current you want, to estimate the voltage drop. If it's not acceptable, try larger wires or stop having things so far away ;). Or of course use a much higher voltage and step down later on, this is what electrical transmission grids do. – KyranF Oct 12 '14 at 11:22
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@KyranF I wish your answer was an answer, instead of spread over 3 comments. :) – Ben Miller Oct 12 '14 at 12:24
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@BenMiller aww, mate i'll make it an answer then. – KyranF Oct 12 '14 at 12:29
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Using an online calculator which is based off some MIL standard for current carrying capacity of copper wires, given some parameters, I came up with 12AWG as the suitable wire gauge. This is approximately 2mm diameter core if you use metric system. This, given a 25 degrees Celsius ambient temperature and a wire length of 1 meter (2.5 feet) as some parameters, resulted in 23 Amp current carrying capacity.
These values are for a 10 degree Celcius rise in temperature in the conductor, and are part of the fitted curve of empirical test data some people took a long time ago for this sort of information which later went into the MIL Standard current carrying wire gauge charts.
If you can afford more temperature rise, you can get away with smaller cores, also if your peak current is only 20A, and not continuous.
If your application is sensitive to voltage drop - for example if you have a 10V regulator you really don't have much spare voltage headroom, every 100mV dropped can be bad for your 10V output. Be careful about the estimated cable resistance (given by the nice online calculator) and use Ohms law with the current you want, to estimate the voltage drop. If it's not acceptable, try larger wires or stop having things so far away ;). Or of course use a much higher voltage and step down later on, this is what electrical transmission grids do.
As for joining wires, using a screw socket terminal strip is pretty good! Maybe some shrink wrap to keep contacts from touching. This solution is very cheap, and can be found from almost any automotive supplies store (people often do this stuff for auto wiring, like trailer light harnesses etc) or hobby electronics shop.
KyranF
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Cheapest and safest don't usually converge.
I prefer a nice gas-tight butt splice using AMP FASTON barrel splices and a good crimper:
EM Fields
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But the ones in your photo are Thomas and Betts. What's that about? Lol – Spehro Pefhany Oct 12 '14 at 13:42
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