best ramps 1.4 headbed mosfet upgrade

Nikki81

best ramps 1.4 headbed mosfet upgrade
June 16, 2015 05:01AM

Registered: 9 years ago
Posts: 198

What is the best mosfet to use to replace the stock one on a ramps 1.4 I have had a good look round the net and found people saying different parts number but ive gone and just confused myself. which one will give me the best performance and reliability ?

thanks Nikki

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o_lampe

Re: best ramps 1.4 headbed mosfet upgrade
June 16, 2015 10:44AM

Registered: 8 years ago
Posts: 5,232

I have two different FETs on my RAMPS:
IRF3205
P55NF06
On first glance, the IRF is better, but they both lack in performance, when the Vgs is lower than 5V.
It is a common problem with arduinos, that their 5V supply is weak. I would try to adress this issue first.
Then even the cheaper FETs are up to the task.
-Olaf

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dc42

Re: best ramps 1.4 headbed mosfet upgrade
June 16, 2015 10:59AM

Registered: 10 years ago
Posts: 14,672

IRLB8743pbf and IRLB3034pbf are good choices. IRF3205 and P55NF06 are bad choices, because they don't have guaranteed performance at 4.5V gate drive.

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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cdru

Re: best ramps 1.4 headbed mosfet upgrade
June 16, 2015 11:34AM

Registered: 10 years ago
Posts: 869

I switched to the IRLB8743pbf a while back for my bed that draws 15amps. I have a fan that blows across the whole RAMPS board and the tab isn't even warm without a heatsink. With the default MOSFET and a heatsink, it would be almost uncomfortably warm to touch even with the fan blowing on it.

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o_lampe

Re: best ramps 1.4 headbed mosfet upgrade
June 16, 2015 11:34AM

Registered: 8 years ago
Posts: 5,232

dc42 is right, there are better choices! thumbs up

But still, if one is shy of soldering:

Would it help to route a 5V wire from a PC-PSU to the RAMPS servo connectors to stabilize arduinos 5V? ( Not the 5V stdby wire )
I also have a 5V/5A UBEC circuit from my RC-multicopter. I can power that by the 12V/30A PSU.
Would I get ground loops then? USB still connectable?
-Olaf

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dc42

Re: best ramps 1.4 headbed mosfet upgrade
June 16, 2015 02:08PM

Registered: 10 years ago
Posts: 14,672

Quote
o_lampe
Would it help to route a 5V wire from a PC-PSU to the RAMPS servo connectors to stabilize arduinos 5V? ( Not the 5V stdby wire )

Running servos form the Arduino Mega's 5V supply is an extremely bad idea. The 5V regulator on the Arduino cannot power servos without overheating. Even powering some LCD displays makes it get too hot.

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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Nikki81

Re: best ramps 1.4 headbed mosfet upgrade
June 16, 2015 04:46PM

Registered: 9 years ago
Posts: 198

Thank You ive just ordered some IRLB3034pbf

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o_lampe

Re: best ramps 1.4 headbed mosfet upgrade
June 17, 2015 05:45AM

Registered: 8 years ago
Posts: 5,232

Quote
dc42

Quote
o_lampe
Would it help to route a 5V wire from a PC-PSU to the RAMPS servo connectors to stabilize arduinos 5V? ( Not the 5V stdby wire )

Running servos form the Arduino Mega's 5V supply is an extremely bad idea. The 5V regulator on the Arduino cannot power servos without overheating. Even powering some LCD displays makes it get too hot.

You are right, but that wasn´t the question.
Please read carefully, what I asked.... smiling smiley

-Olaf

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dc42

Re: best ramps 1.4 headbed mosfet upgrade
June 17, 2015 06:43AM

Registered: 10 years ago
Posts: 14,672

Quote
o_lampe

Quote
dc42

Quote
o_lampe
Would it help to route a 5V wire from a PC-PSU to the RAMPS servo connectors to stabilize arduinos 5V? ( Not the 5V stdby wire )

Running servos form the Arduino Mega's 5V supply is an extremely bad idea. The 5V regulator on the Arduino cannot power servos without overheating. Even powering some LCD displays makes it get too hot.

You are right, but that wasn´t the question.
Please read carefully, what I asked....
-Olaf

OK, so you want to use the 5V servo power pin as an input to feed 5V to the board. Yes that would help. It's probably a good idea to remove the diode that feeds 12V to the Arduino from the RAMPS board if you do that.

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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