1.0 mm diameter copper (AWG 18 ?) - Page 1
Forum section: electronics / beginners

author: made2hack
author_rank: Frequent Contributor
timestamp: February 08, 2014, 01:03:26 pm
content: Hello,I've got to put through around 2000mA (actually 1600mA) but, for argument's sake, 2000mA of 12VDC which is boosted to 40VDC. Final output is 39V @ 1.6A.Is 1.0mm diameter copper flexible (not solid core) wire sufficient? I think this is like AWG 18, but I'm not familiar with the AWG scale.Am I ok using this wire? The lengths is max 50 - 60 cm, no longer than 1m. I think the voltage drop will be ok, but I am concerned for the amperage going through.

author: Monkeh
author_rank: Super Contributor
timestamp: February 08, 2014, 01:56:46 pm
content: Quote from: trs80 on February 08, 2014, 01:03:26 pmNot with 12V 1.6A in, it's not.

author: denelec
author_rank: Regular Contributor
timestamp: February 08, 2014, 03:19:39 pm
content: 1mm diameter is indeed about 18AWG.The resistance will be around 20 ohms/km.It's going to be fine for 1.6A.But if you output 1.6A @ 39V, the current will be much higher at the 12V input.Since P=VI, 39V * 1.6A = 62.4WThe power at the input will be higher than 62.4W since the conversion is non 100% efficient.Assuming a 90% efficiency, the current at 12V will be: I = 62.4W / 12V * 110% = 5.7A.18AWG should also be fine for 5.7A.

author: mariush
author_rank: Super Contributor
timestamp: February 08, 2014, 04:06:24 pm
content: 18 AWG is used by power supplies. A power supply sends 12v up to 150w to a video card through three yellow cables so each of those wires is meant to deliver 4A+ for long periods of time with no problems. 5-6A will be fine.However, follow denelec's post above me. 12v 1.6a in does not mean 39v 1.6a out .. can't raise voltage without lowering current, you can't have higher voltage without raising input current.

author: made2hack
author_rank: Frequent Contributor
timestamp: February 08, 2014, 11:30:20 pm
content: Thanks for the reply. I forgot that the 12V in doesn't provide 1.6A but moreSo, my project is essentially to 6 LEDs from a 650W PC PSU, like the one here:Now, mine is the 650W version but the power rail is the same, 12V / 18A / 450W. Does anyone know exactly what that means? I mean does it mean that every Molex connector can output 12V @ 18A? Because that would be 216W x 4 = 864W on the 12V Rail. Which doesn't make sense. Or is it that each rail can supply a maximum of 18A ? If I were to divide the 450W / 4, it would mean that max that each rail can give is 112W @ 12V (or about 9A)?Say that I want to drive 2 LEDs on 1 rail, so as per #denelec's efficiency of 90% I would use 12V @ 10.4. Can I then use another rail to do the same: another 10.4A? And finally a third?So 3 rails, using 10.4A each, for a total of 31.2A @ 12V or 374.4 W ?? Or is the PSU going to die after 18A? Or does my PSU reasoning not work? Is the current split some other way?

author: Psi
author_rank: Super Contributor
timestamp: February 08, 2014, 11:35:29 pm
content: It means each rail can supply a max of 18A but the total power over all 4 outputs can't be higher than 450W.The 3 separate black lines you can see on the label show which outputs share their power and which are seporate.That psu likely has 3 separate transformers inside.Assuming the label isn't lying about the specs yes, drawing 9A from each of the 4x 12V rails at the same time would push the psu to its 450W limit. (You could still draw more from the 3.3V 5V -12V and +5VSB outputs though)In reality most computer powersupplys cannot handle what they say.If you try they protect themselves and switch off, then you have to unplug them from the wall and wait a few minutes for the caps inside to discharge so that the chip resets itself.

author: made2hack
author_rank: Frequent Contributor
timestamp: February 08, 2014, 11:53:52 pm
content: So if I'm drawing 31.2A (10.4) from 3 of the 4, I should be ok? Since 320W out of the 450 is good enough head room?I added a link to the manufacturer:http://www.inter-tech.de/index.php?option=com_content&view=article&id=615%3Aenergon-eps-650w&catid=125%3Aausland-atx-netzteile&Itemid=542&lang=en

author: mariush
author_rank: Super Contributor
timestamp: February 08, 2014, 11:54:21 pm
content: The label is fake on that power supply.For continous use, I would give it maybe 12-14A at 3.3v (30-40w), 10-12A at 5v (50-70w) and maybe 350w at 12v (about 30a).The power supplysaysit has 3 rails, each can do up to 18a but can't all stay at 18a at same time. Ideally, one rail is dedicated to the ATX 24 pin connector + a 4-8 pin cpu power connector, one rail is dedicated to the PCI Express 6 pin or 8 pin connectors, and the third rail is dedicated to sata and molex connectors.In practice, it would be best to open the power supply and post some pictures here with the front and back of the pcb because a lot of such crappier power supplies aren't really split on 3 rails but rather have just one chunky rail capable of doing those 30 amps. They're just lying on the label about the rails being split.In this is the case, then you don't have to worry and you can just cut the connectors off and use the yellow wires to drive your leds.

author: made2hack
author_rank: Frequent Contributor
timestamp: February 16, 2014, 03:01:08 pm
content: I have uploaded pictures to this new thread:https://www.eevblog.com/forum/beginners/am-i-getting-18a-from-this-psu/if anyone has any ideas, can we move the conversation to that new thread?Thank you!!!