how is it possible to use other motors as the provided nema 17: nema 14 or 8.... only a firmware and eeprom change possible?

how is it possible to use other motors as the provided nema 17: nema 14 or 8.... only a firmware and eeprom change possible?  

Active Member

Hi there,

I have ordered the mini but I would like to go with a real direct extruder instead of the bowden one.

I see different option possible... one could be using a flex3ddrive with a nema 8.  not a bondtech one.

Don t try to explain me about the worth print I will possibly get.

I would like to try.


But the problem will be setting the max current on the board sothat the motor can maintain a torque without burning/dying it, isn't?

(A nema 17 can same torque than a nema 8 but with less heat release...  said in a simple language maybe not completely true)

Meaning changing some values of the firmware by hand. Maybe the eeprom....

I have the impression from what I read both are not possible. only prusa release update. that you can upload and that is all.

Except if you break a small piece of the controllboard which secures the board from implementation of other firmware.

I just want to change the max current (decreasing it). But keeping the same firmware otherwise (a slightly customed firmware tgen)


Maybe it is possible through the prusaslicer? That the gcode is set sothat the printer will not overload a weaker motor.


Any ideas?

Maybe someone know a trick to keep the nema 17 settings in the firmware but by changing something in the hardware?

(adding a resistor on the alimentation cable of the motor? I did that to reduce the volume of a  non dimmable loudspeaker of a toy... the code-a-pillar from fisherprice... this toy was so loud... much better now, although we hear the motors of the toy when it is moving...maybe this was the reason-covering the noise of the motors... nevertheless. It worked here...

do you think this could be possible to reduce physically the current by adding a resitor???)

I will really appreciate a feedback

Thank you in advance.


Best Regards






Posted : 23/01/2021 8:51 pm
Eminent Member

I think you can change the maximum current by swapping the current sensing resistors for an appropriate value (see TMC2209 datasheet, chapter 8). This would involve soldering on the buddy board. I don't know if scaling via software is possible, that depends on the exact configuration of the motordriver which I am not sure about.



Posted : 26/01/2021 10:50 am
Estimable Member


M906 allows You to set the motor current, rsense and microstep are instead adjustable by modding the firmware.

Posted : 26/01/2021 9:42 pm
Active Member

So I received my mini. I did not change anything yet.

I am however still thinking about mounting a direct extruder like the one of the easythreed on top of the hotend (over the heat sink)

I still need to figure out how to go around this without damaging the buddyboard.

One further idea: with custom print profile (retractation maybe)-->

Use the cabling for the current bowden motor, add a physical interface  (a small piece of pcb/ a sparkfun part?)

Enabling to decrease the power, set a maximum value of power in order to avoid burning the motor.

As a kind of translator.

The e steps will be set though the gcode. In order to modify as little as possible....




Posted : 10/03/2021 7:26 pm

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