Recommended DIY wire/cable material for PSU - Page 1
Forum section: electronics / general

author: kalel
author_rank: Frequent Contributor
timestamp: January 12, 2018, 01:32:52 am
content: I couldn't find an affordable standard quality cable for an adjustable PSU locally, so I would like to build one that is as affordable as it can be while satisfying the basic requirements.My question is about the recommended cable/wire to use for this. It needs to endure up to 5A and/or 30V without internal melting.There's no need for it to be very long (I assume around 1M-1.5M is fine for this, give or take a little).I assume stranded is the only option here. PVC and similar insulation is much cheaper than rubber/silicone etc, but if those are crucial according to your recommendations, I will check if there is an affordable solution with that type of insulation.A lot of the wire size calculators seem to target AC and minimum voltages of 110V, but I found this:http://www.solar-wind.co.uk/cable-sizing-DC-cables.htmlWhen I type in 1% acceptable loss, 30 VDC, 5Amps, 1.5Meters, I get: 1.5mm² / AWG 17 (11A max).11A max seems a lot more than 5A however and too much thickness will hinder flexibility. But, perhaps this extra amperage capability is necessary for some reason? To handle some peaks? When I type in 1A, it recommends 0.5mm^2/24AWG (5A max).

author: thermistor-guy
author_rank: Frequent Contributor
timestamp: January 12, 2018, 02:55:05 am
content: For low-voltage power wiring and prototypes, I scavenge the insulated conductors from the mains cords of newly failed appliances. The cord has the electrical ratings and regulatory approvals printed on the outer jacket, so you can tell if it's fit for purpose. And it's free.I add a small length of coloured heatshink tubing near both ends of the conductor (just before installation), to identify it as not carrying mains.Need to carry more than rated current? Parallel them up.

author: Muttley Snickers
author_rank: Unknown
timestamp: January 12, 2018, 03:56:53 am
content: One of my customers builds truck trailers so I have a good supply of multi-coloured heavy gauge trailer cable whenever I need it, I always keep a roll handy just in case.Narva Cables.http://www.narva.com.au/products/browse/cables

author: sleemanj
author_rank: Super Contributor
timestamp: January 12, 2018, 04:21:22 am
content: If your bus voltage is 30v, and you can tolerate a 1% loss at 5A, then...30*0.01 = 5 * R.3 / 5 = R0.06 = Rthe total resistance of your cable "there and back" need to be 60 milliohms or less, if total wire length is therefore 3m, you need a resistance under 20 milliohm/M or less.https://en.wikipedia.org/wiki/American_wire_gauge#Tables_of_AWG_wire_sizesConsulting the AWG chart at wikipedia above ( for copper wire ) that's going to be in the AWG 17 - 18Over that 3m, you will at the rated current of 5A be dissipating W = 5 * 0.3 = 1.5W, not exactly a massive amount of energy spread out over 3 meters of copper wire.That gauge of wire will at a minimum handle 10A according to the wikipedia table, so you can see that your limitation is not the "ampacity" but the losses you have specified (and length of wire).

author: BravoV
author_rank: Super Contributor
timestamp: January 12, 2018, 04:30:50 am
content: On a few occasions in the past, I used car booster cables, as they're quite long and cut to suitable length.Even the cheap one is still not bad as they have the silicone type insulation and not stiff at all as it uses stranded wires inside.Random image grabbed from Google

author: kalel
author_rank: Frequent Contributor
timestamp: January 12, 2018, 04:52:49 am
content: Quote from: sleemanj on January 12, 2018, 04:21:22 amMakes a lot of sense, thanks.

author: ez24
author_rank: Super Contributor
timestamp: January 12, 2018, 05:17:11 am
content: I am also wiring up a PSU and I have chosen 18 ga stranded. 16 was too big to solder small parts to and I just felt that 20 was too small. So 18 was a compromise for me. Another thing is if I get "bad" wire that is really 20ga then it won't hurt.I also bit the bullet and ordered some shielded Belden wire.