Powering Heated Bed?

Hi all,

I just got my heat bed fixed to my prusa mendel v2. I currently have an old laptop charger powering my motors and fans and it seams to be working fine. I am unsure how I power my heated bed? can I use another laptop charger? I am also unsure where this extra power source will plug in. Does it wire into the 11A terminals or does it plug direct into the arduino board.

I currently have the laptop charger wired into the 5A terminals.

Any help would be appreciated.

Thanks,
Adam

Edited 1 time(s). Last edit at 10/18/2013 11:33AM by adamlister.

Your additional power supply would wire into the 11A terminals. This powers only the heated bed. Just make sure that your additional power supply can supply at least 12 amps, preferably 15 amps or more to be safe.

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many lcd tv adapters exist. i have one that is 12v, 12amps. it works ok on one of my heated beds. a laptop supply is likely between 18-24v, and will be too high of a voltage.

The easiest way is to simply buy a PC power supply with 18 or more amps, you can find them pretty cheap (I usually buy them for about $5-10 at a small electronics shop near where I live).

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I just noticed that the red wire from my PSU for the heated bed is getting so hot at the plug input that it starts to melt the plastic and lose contact with the RAMPS board. Is this just because the wire gauge is too narrow to carry the full current, or is there an unusual amount of resistance at the plug? The wires are typical gauge that you find in an ATX PSU but are not as thick as the wires from the RAMPS to the heated bed, so I suspect the wire gauge is the main issue. My PSU is an adjustable LED Strip PSU set at around 12V. The PSU can handle 30A, but I don't think it's pushing that much current at all times, just what the circuit draws. Anyway, obviously current is being wasted as heat with these wires, so I'm going to try a thicker gauge. I used to use an ATX PSU with 12V at 15A but switched a few months ago. I'm not sure this issue popped up with the older PSU, but I guess it couldn't produce as much current as the new PSU.

I'm posting here in this thread since my issue is topical, and this is something we need to watch out for in our bed wiring, either double it up or use a heavier gauge. I suppose this can also be an issue if the point of contact in the plug is too small.

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I recommend minimum 4 standard ATX cable leads for the bed. Per cable... so 4 yellow and 4 black. (20 AWG on myne)

3 maybe be enough if you have some of those high current 4 pin 12v connectors (18AWG on myne)



You dont want those wire to heat up at all, as it will reduce the power getting to your bed.

Also make sure your screw terminals are tight. Cable must not be a loose connection. Loose connections are how fires start

That burned terminal image is a good warning! The wire might just not be making good contact at the screw terminal, and I might want to get a new plug or two anyway, just in case this one melts any more. A heavier gauge of wire will certainly do something, given how it's heating up at the plug. Strangely, this has only been a noticeable issue very recently. For a few months, maybe a dozen prints, I didn't notice it at all. In a way it's lucky the contact started to melt, otherwise it might have gone unnoticed until it burned up.

That's something interesting, that I've noticed; Everyone says you need x length of wire to hook everything up, but no one says what gauge wire you need.

Are there any "official" specs on the wiring harness for these bad boys? I realize that there will be different specs, depending on supply voltage, electronics used, etc. But to have *some* sort of guide to use as a starting place... that would be a big help.