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3d printer unable to power the heatbed and the hot end simultaneously.

Posted by MMS 
MMS
3d printer unable to power the heatbed and the hot end simultaneously.
September 04, 2017 01:23AM
Hi, Long time lurker first time poster. I'm having some difficulty with powering the heatbed and hot end at the same time. I can power the heat bed up to temperature independently and the hot end independently. However, when I try to power both for a print the RAMPS and Arduino both suddenly turn off. Setup:
- Prusa i3 clone
- RAMPS 1.4
- Arduino MEGA OEM
- A4988 drivers for X,Y, Z
- DR8825 for the extruder
- 12v 20A PSU
When it happend the RAMPS and Mega turn off but the PSU remains on. The MEGA stays off and the computer can't read it through the USB until I heard a click 10 minutes later and then it would recognize.

When i first wired up the RAMPS and turned on the heatbed the stock mosfet on the board started smoking and completely fried. So I upgraded that mosfet for the heatbed at D8 with a IRLB8734Pbf which didn't provide any power to the bed at all. I figured the ramps must have been damaged and replaced it with a brand spanking new one and soldered a new IRL8734Pbf onto it.

Then I found that the new power supply had no problem powering the motors but as soon as I tried powering the heatbed, the PSU would start switching off and on every second. When I checked the voltage across the bed I was seeing intermittent spikes of voltage ~0.5-5v. So then I swapped the new PSU with an older working one from another printer which finally heated the bed up to temperature. But as soon as I try to run the hot end as well the mega shuts off (the PSU remains on). I'm thinking it may have something to do with the 5v pinout from the mega but I'm at a bit of a loss as to what to do next and how to fix it. Any help would be greatly appreciated.

Edited 2 time(s). Last edit at 09/04/2017 03:12PM by MMS.
Re: 3d printer unable to power the heatbed and the hot end simultaneously.
September 04, 2017 03:45AM
GET A BIGGER POWER SUPPLY!!!

12v 15A is pathetic.

most 200x200 12v beds are about 11amp, the rest is 5amp. That is 16 real amps.. since most power supplies are lucky to get %75 of rated capacity.
Need at least a 20amp supply, preferably 30amp

Edited 1 time(s). Last edit at 09/04/2017 03:50AM by Dust.
MMS
Re: 3d printer unable to power the heatbed and the hot end simultaneously.
September 04, 2017 03:10PM
Sorry the PSU that I'm using now is 20A. I swapped out the 15A one that didn't work. Also, I'm concerned about the Arduino MEGA I'm reluctant to get a more powerful PSU and completely fry the mega.

Edited 1 time(s). Last edit at 09/04/2017 03:47PM by MMS.
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