Hi,

Other than the power-input I provide to the mosfets, is there a max DC current that i can run through them?

“Todd Mitchell”



Ray Kholodovsky (Cohesion3D) December 14, 2017 19:25

Motor drivers are rated ~35v, voltage regulator and mosfets are 40V rated.

In general I do not recommend putting more than 30v anywhere.

If you need higher values, why? and then you will probably want a different solution.


Todd Mitchell December 14, 2017 19:33

Just looking at options for what I can control digitally rather than a large switch box.

Pump for water cooled spindle

Couple of fans

Perhaps Low voltage lighting for the case


Ray Kholodovsky (Cohesion3D) December 14, 2017 19:41

In my experience if these things are not 12/24v then they will be AC powered in which case - SSR or Relay


Todd Mitchell December 14, 2017 19:56

Agreed. I’ll use a relay for anything outside of that range. I still need to know what sort of current I can handle with the mosfets tho? Do you have any ratings?


Todd Mitchell December 14, 2017 19:59

I.e. I want to run this water cooler directly from the cohesion board without a relay.

It’s 19W @ 12v so looks like 1.6A

amazon.com - Robot Check


Ray Kholodovsky (Cohesion3D) December 14, 2017 20:04

That’s fine.

For ReMix I specified ~3 amps per bottom row mosfet making for a total of 12 amps in thru the pluggable input terminal at the bottom left.

The FETs themselves are capable of 14 amps, each output terminal is 8 amps… If you need more than 12 amps in total across the bottom row, let me know.


Todd Mitchell December 14, 2017 20:23

+Ray Kholodovsky Curious - if the FETs are 14 and terminals are 8, what is the constraining factor keeping it at 3 amps?


Ray Kholodovsky (Cohesion3D) December 14, 2017 20:28

The maximum rating of the input terminal - 12 amps / 4 amps = ~ 3amps per if used “uniformly”

Of course you can bypass this by manually feeding the + voltage to each device (ie: do not hook anything up to the + on the output terminal, those just redistribute the same +VMOSFET you put into the input terminal).

Now you need thick ground wires at the remaining 2 power input terminals (main and bed), are limited by the 8 amps each of the mosfet output terminals and the total draw on ground through everywhere. And heat. There will be heat.


Todd Mitchell December 14, 2017 20:36

Thanks for the explanation. Sounds like it’s easier and less risky to just use SSRs


Ray Kholodovsky (Cohesion3D) December 14, 2017 20:39

Eh, I think devices up to a few amps like the one you linked is fine. We’re doing 3.3 amp heaters for a 3d printer anyways.


Todd Mitchell December 14, 2017 20:51

Yes, I agree. I was speaking about the larger items. I’m happy to drive it up to 3 amps. that should get me fairly fare in avoiding a switch panel. I’m using a wall-wart from the thrift store rated at 12vdc 6A so that’s my max for now which should be fine for LED panel, water pump and alignment alignment lasers


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