MK2B Heat Bed, 12V 30A power, ramps burn

Hi;

I have ramps1.4, 12V 30A power, my heat bed is 1-1.2ohm. When I heat the bed its drawing too much current and ramps burns. I dont have any external Mosfet. Is there any option to controld the current for the heat bed with Repetier or Marlin?

How much current do I need for heating my bed?

I have burned 3 ramps and 1 arduino mega because of this problem. Is here any way ro fix my ramps? Only mosfet has burned.

Buy an external mosfet, or change ramps bed mosfet for something better than the low quality one provided. eg IRLB8743 IRLB3813

Quote
Dust
Buy an external mosfet, or change ramps bed mosfet for something better than the low quality one provided. eg IRLB8743 IRLB3813

Very useful, I didn't know about these ones. Are they drop-in replacements? In that case I'll order a bunch to replace some on my old Ramps boards

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http://www.marinusdebeer.nl/

Read a lot about the mosfet's and decided to go with the IRLB8743! I'll update how it goes once it's installed

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http://www.marinusdebeer.nl/

I had a similar problem with my ramps compatible controller.
What came to my mine was a heat sink for the mosfet, I decided on straight bar aluminum and mounted it to all four mosfets using transistor mounting kits.




I also designed a controller case an added a cooling fan to ensure my mosfets stayed cool.
It is now going on the 4 year and have never felt the mosfet hot and have 3D Printed 7 hours models.
My 3D Printer is in an temperature controlled enclosure so I can get better layer adhesion results when 3D Printing ABS.

Sample ABS 5+ Hour printed Model

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Computer Programmer / Electronics Technician

Ramps mosfets are unfortunately not in a line... and tightly packed... difficult to add any substantial heatsinks. Better to not produce the heat in the first place.

Another easy solution is to run the power to the head bed through a relay. These automotive cube type relays are rated for millions of cycles and
are relatively quite when activated. You would need to enable Bang-Bang mode in the firmware and it never hurts to add a fly back diode across the relay coil.
The wires to the relay coil are hooked up to the terminals on the controller that you would normally power the heat bed with.

And add a inline fuse holder and fuse.

Edited 2 time(s). Last edit at 08/30/2020 06:43AM by Shank man.

The Ramps 1.6 mosfets are in a straight line.

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Computer Programmer / Electronics Technician

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