Heatsink for Mosfet

Fizpok

Heatsink for Mosfet
December 18, 2016 12:51PM

Registered: 9 years ago
Posts: 120

Hi,
As I understand, I need a heatsink for D8 mosfet. What kind should I use?
For example, if you look at ru.aliexpress.com for heatsink for mosfet, you get different sizes, plus some of them use bolt and some - a sticker.
Anyway, suggestions, comments or a direct link at Ali are welcome.
Thank you.

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dc42

Re: Heatsink for Mosfet
December 18, 2016 04:28PM

Registered: 10 years ago
Posts: 14,672

If your bed heater mosfet is getting hot, a much better solution is to replace be MOSFET with a better one. The MOSFET specified in the ramps documentation is a terrible choice. A few of the more expensive ramps boards are built with better MOSFETs, such as IRLB8743.

Better still, if you can afford it, ditch the Arduino/ramps and get a modern properly-designed 32-bit contoller board.

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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Fizpok

Re: Heatsink for Mosfet
December 19, 2016 01:27AM

Registered: 9 years ago
Posts: 120

Which mosfet should I use and which 32 bit board?

Quote
dc42
If your bed heater mosfet is getting hot, a much better solution is to replace be MOSFET with a better one. The MOSFET specified in the ramps documentation is a terrible choice. A few of the more expensive ramps boards are built with better MOSFETs, such as IRLB8743.

Better still, if you can afford it, ditch the Arduino/ramps and get a modern properly-designed 32-bit contoller board.

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dc42

Re: Heatsink for Mosfet
December 19, 2016 03:07AM

Registered: 10 years ago
Posts: 14,672

Good MOSFETs to use on a RAMPS include IRLB8743pbf and IRLB3034pbf.

As for 32 bit controller electronics, I'm biased but I recommend the Duet WiFi for its high current 256x microstepping stepper drivers, built in web interface, and its high processing power and large ram which means is has the capacity for new firmware features.

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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Fizpok

Re: Heatsink for Mosfet
December 19, 2016 05:42AM

Registered: 9 years ago
Posts: 120

I'll try mosfets. As for Duet WiFi and likes, the only problem is that I already have figured out everything about Arduino-RAMPS smiling smiley

As for my case: what else should I check if D8 not working? I mean, before changing the mosfet? What else can burn: resistors, wires on RAMPS, Arduino's pins - and how to test it?

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dc42

Re: Heatsink for Mosfet
December 19, 2016 03:18PM

Registered: 10 years ago
Posts: 14,672

You could use a multimeter to measure the voltage between the gate and source terminals of the MOSFET. That's the two outer terminals. It should be 5V when the bed heater is supposed to be on, and 0V when it is supposed to be off.

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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Fizpok

Re: Heatsink for Mosfet
December 21, 2016 12:31AM

Registered: 9 years ago
Posts: 120

0V in both cases. What does it mean?

Quote
dc42
You could use a multimeter to measure the voltage between the gate and source terminals of the MOSFET. That's the two outer terminals. It should be 5V when the bed heater is supposed to be on, and 0V when it is supposed to be off.

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dc42

Re: Heatsink for Mosfet
December 21, 2016 03:13AM

Registered: 10 years ago
Posts: 14,672

It looks like either the Arduino D8 output is no longer working, or you have a bad connection somewhere between the pin on the microcontroller on the Arduino and the MOSFET gate pin. But also check for continuity between the MOSFET source pin and ground.

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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