Big Mosfet Question

Controllers Smoothie
1

Please excuse my ignorance, but is it possible to share a load between 2 big mosefts? I am looking at heated bed options for my printer and the one I would like to get has a resistance of 1Ω… Running at 12V, it’s right on the 12A current limit of the connectors. If it’s a no go, is it possible to get higher rated connectors? The mosfets are rated at 20A but what about the PCB?

I have ordered a cheapo SSR (SSR-40 DD) but read that these drop about 1.6V and could run very hot.

Just to clarify, I don’t want a mains voltage heated bed, it has to be 12V.

Regards,

Les

Imported from wikidot

2

This doesn’t answer your question, but I suggest you consider running the heated bed at 24V. You can run the big Mosfet at 24V and continue to use your current 12V elsewhere.

3

Hey.

You definitely can’t use the two mosfets together, and definitely want to use a SSR in this case.

Cheers.

4

Thanks for the reply.

Sorry for more stupid questions, I just like to know why.

Is it because it’s not electrically possible or because of a firmware limitation?

Regards,

Les

5

It’s not electrically possible, it was not designed for this, the traces are not thick enough, etc.

6

Thank you for the clarification. :slight_smile:

7

I ordered this very big MOSfet for my 400W bed, it works well for me:
I can’t put a link, so google:
“3D printer parts heating-controller MKS MOSFET for heat bed/extruder MOS module exceed 30A support big current”
It has opto-coupler so you can use it at different voltages and it is <10$
SSR are better for much higher voltages (>100V)

8

I was kinda thinking of doing the same thing. I have some VBFM (very big friggin mosfets) i was using to build monsterous ECig mods at extremely high amperage, was considering hooking up one of those. (should EASILY support 24v at 20 amps (can take truly massive amps without heatsink). Much cheaper than a 30 dollar SSR.

Might be a little overkill… but I really want the spindle controllable via smoothie. Think the hardest thing is gonna be figuring out how to wire it up and what size resistor I need on the legs to drain it when switched off.