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0.7 Ohm 12V Heatbed? Mk3

Posted by WesBrooks 
0.7 Ohm 12V Heatbed? Mk3
January 04, 2019 03:44AM

Had many troubles with a kit I purchased early december. This is a P3Steel based kit with RAMPs. Just soldered the 14awg heatbed wires on and checked resistance. I'm only seeing 0.7Ohm? I thought this was a short but nothing visible and no shorts to the aluminium. Checked the expected load and wattage and it is neatly 200W (allowing for errors) and would draw 17A. The neatness to 200W leaves me suspecting this is as designed and the tracks do seem wider than my other secind hand mk3 bed.

Any one else seen these high current 12V beds?

I'll raise the issue with the supplier too.
Re: 0.7 Ohm 12V Heatbed? Mk3
January 04, 2019 04:11AM
The tracks are just resistance, if you have thinner thickness copper in the Z direction you can have the wider tracks

Are you sure your meter reads resistance correctly when that low? most don't.
Re: 0.7 Ohm 12V Heatbed? Mk3
January 04, 2019 04:33AM
Yeah, big margin of error, but the other plate I have measures near double the resistance.

I expect this is an aliexpress style job. Manufacturer isn't obvious.
Re: 0.7 Ohm 12V Heatbed? Mk3
January 12, 2019 05:14PM
System now running with a 20A fuse and a 30A MOSFET from a 25A power supply through 14awg silicone insulated wire. All seems fine and completed a few autotune cycles with no issue. Build trials next week and I'll try to figure out a 20A+ thermal snap switch for 130C ish.

Doubt all would have been fine if I'd built the kit with the sub 14awg wire, no fuse or mosfet.
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