Welcome! Log In Create A New Profile


Mosfet Burn

Posted by RicardoGA 
Mosfet Burn
May 25, 2013 03:01AM
hi my ramps 1.4 have a mosfet burn (heatbead) but in my city is hard to find electronic parts i dont know much about electronics so i want to ask if this mosfet can be use insted of the stock of ramps

Stock IRF512

4.9A, and 5.6A, 80V and 100V, 0.54 and 0.74 Ohm

Replacement IRF640

N - CHANNEL 200V - 0.150Ω - 18A

Thanks in advance
Re: Mosfet Burn
May 27, 2013 04:53AM
How much current does your heatbed draw?
Re: Mosfet Burn
May 27, 2013 02:04PM
12V 10 amp the heatbed is mk2b
Re: Mosfet Burn
May 27, 2013 05:27PM
Ok then it's no suprise for me that the IRF512 damaged. You need a very big heatsink to handle 10A.

For the IRF640 you will need also a quite large heatsink: at least around 6K/W.

Try getting a Mosfet with a RDS(ON) smaller or equal than 0,018 like the STP55NF06 which is used in the most Ramps boards. This one should work, even without a heatsink. But you can add a small 27K/W one just to be safe.
An alternative Mosfet would be the IRL3803 with a RDS(ON) of 0.006.

Edited 1 time(s). Last edit at 05/27/2013 05:41PM by johni85.
Re: Mosfet Burn
May 28, 2013 05:34AM
ok thanks for the assintence i found this irf 3205with rdson .008 and work great in the hotend and the fan the but with the heatbed i have a problen as soon as i turn on the heatbed the power supply (power switching (led) 12v 30 A) shut down the power and when i disconnect and connect the power supply to restablish the power the mosfet is blowed i tried dierent mosfet like irf 3205, irfz44n, p60n06 with the same problem i dont know what could be
Re: Mosfet Burn
May 28, 2013 06:46AM
That looks lika a shortcut. What is the resistance of your heatbed? I had a similar problem with a new heatbed which has a too low resistance. But it only killed my mosfet. The power supply was strong enough. You can also try to connect for example a fan to the heatbed connector to test if somethimg is wrong with the Ramps board.
Re: Mosfet Burn
May 28, 2013 11:28AM
i put a heater cartridge and work without a problem dont kill the mosfet and the cartdige heat normal the resistance in the heatbead is 1.4ohms
Re: Mosfet Burn
May 28, 2013 05:17PM
also i connect the fan and work ok but as soon as i try withthe heatbed the problem appear again the power shut down and the mosfet blow
Re: Mosfet Burn
May 28, 2013 09:11PM
Found the problem and solved
The problem was the pcb Heatbed this has a short the solutions has changed the pcb heatbed
Sorry, only registered users may post in this forum.

Click here to login