Power Supply Requesites

Hi,

I'm mounting a reprap prusa i2 with a PCB Heatbed MK2a, but I've heard that some power supplies don't have enough power to heat this hotbed and make the rest of the electronics work. I would like to know if my power source will work properly or it will break.

My PC power source is an AT 300W.

Since then, thanks.

Well the rule of thumb is leave 10Amps for the heatbed. That is 120W.

The most recommended one is 29-30A PSU which is 360W. I am using a 450W PSU from an old computer. Ebay sells them for like 30 bucks or so

The best thing to do would be to just try using your PSU. And if your PSU trips then you know you need to buy a bigger one. Most PSU will reset once they have tripped. So dw about damaging it.

I would make sure the Heatbed has a good resistance value as well. I forgot the value but you can find it on the internet somewhere. My heatbed was 0.01 ohms and was clearly faulty. So when I plugged it in without measuring, my PSU kept tripping.

You need at least 16A on the 12V rail to run a heated bed with the rest of the electronics. Look at the sticker on your power supply, and make sure that the 12V rail can supply at least 16A. A 300W AT power supply may not provide enough 12V power.

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Get a good power supply, like the ones here: [www.trcelectronics.com]

ATX power supplies are not really designed to only have the 12v used, they usually need a load on the 5v for the 12v to regulate properly.

Quote
stephenrc
Get a good power supply, like the ones here: [www.trcelectronics.com]

ATX power supplies are not really designed to only have the 12v used, they usually need a load on the 5v for the 12v to regulate properly.

I second that. The Meanwell supplies are well-made and inexpensive. At $43.60 (+shipping) if you are in the US, it's a great deal. If you aren't in the US, you should be able to find a supplier in your country. You can use knock-off Chinese 12V supplies that are about half the cost, but those are really hit-and miss, and usually don't include proper protection circuitry.

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Hi again!

I've measured the Hotbed resistence, it's 1.6Ohms, is it's ok? The informartion I've found say's that the value is bettwen 1.0 and 1.2 ohms.
And I've mesured the amperage of my 12V rail, it was 12A, seems that I will need to change my power supply, but still I've got some questions. How to avoid problems between my Hotbed and the power supply? Is there any special circuit necessary for it work properly? I ordered a 400W ATX power supply, it didn't arrived yet, but it is very different from my previous one...