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geekhack Projects => Making Stuff Together! => Topic started by: Manroop on Tue, 21 September 2021, 17:50:34
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I have been trying to get into making some DIY coiled cables and have seen that people typically use 28 AWG shielded 4 core with one 28 AWG twisted pair for the data lines, are these important? The only one I was able to source in Canada cost 68$ (CAD for 100ft while the One on Ali express only cost 22.76$ (CAD) for 100ft except no twisted pair, is it important that there is a twisted pair for the data lines?
https://ca-en.alliedelec.com/product/l-com/cbl-usb2-2828-100/70455149/?
https://www.aliexpress.com/item/4000564519029.html?spm=a2g0o.cart.0.0.211d3c00ozlEsd&mp=1
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So, the AWG is related to how many amps you need to run through the cable and the shielded core is mainly a hazard prevention measure.
if you want to know more about AWG, here's a url https://www.techtarget.com/searchnetworking/definition/American-Wire-Gauge (https://www.techtarget.com/searchnetworking/definition/American-Wire-Gauge)
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AWG is to handle amps, but on lower voltages it's also needed to prevent voltage drop.
You aren't going to cause a wire to melt at USB amp/watts/volts but you may not have enough current to actually power the device by the end of that wire.
And yes, wire is expensive, copper is actually rather expensive and it weighs a lot so it costs a lot to ship as well.
Running it through a wire calculator.
For full USB Type A (2.7amps) with a 5% voltage drop:
For 6 feet you ideally need 15AWG, which is WAAAAAY beyond what you actually find in any of them.
3 feet - 20 AWG.
But for a keyboard you really only need .5 or 1 amp, so... (USB 2.0 is 0.9amps?)
1 amp 6 feet - 20awg
1 amp 3 feet - 23awg
For 0.5 amp
6 feet - 23 AWG
3 feet - 25 AWG
Again, few cables actually meet this spec because wire is expensive and it's not like it will catch fire.