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using smaller stepper motor on rambo board?
Posted: Thu Jul 04, 2013 3:18 pm
by spart
hi all just about to get my rambo board and was wondering if any one could tell me dose the rambo board regulate the power for the stepper motors on it own. i have built my own extruder with a smaller stepper motor that i got out of a deck top printer and cant find any info on it. thought i better check before i blow up something lol.
Re: using smaller stepper motor on rambo board?
Posted: Thu Jul 04, 2013 8:20 pm
by Polygonhell
The output current is controlled by the firmware, it's an entry in configuration.h
Re: using smaller stepper motor on rambo board?
Posted: Thu Jul 04, 2013 10:19 pm
by kbob
You can also change the current through a G-code. For the extruder motor, use this.
M903 P3 Snnn
where nnn is a number, 0 to 255. The comments in Configuration.h claim that 135 translate to 0.75 amp, 185 to 1.0 amp, etc.
Do you know what current your motor is rated for?
Re: using smaller stepper motor on rambo board?
Posted: Fri Jul 05, 2013 12:40 am
by spart
this is what i could find on minebea site, went off size cant see number on stepper motor,it is 1/4 smaller then nema 17,
Model =08PM-K049BSTDCN
Step Angle (deg)=1.8
Drive Sequence=BI-POLAR
Rated Current(A)=0.5
Resistance(Ohms) =8.0
Holding Torque(mNm)=20
Inductance(mH)=3.8
Rotor Inertia(g･cm2)=1.6
Detent Torque(mNm)=2
Mass(g)=50
Re: using smaller stepper motor on rambo board?
Posted: Fri Jul 05, 2013 3:43 am
by Eric
20 mN-m is 2 N-cm. That's about 10-15% of the torque you can find in nema-17 motors. For a direct-drive extruder, I don't think that motor will cut it. Geared down it might be ok. Even if it works, I'd monitor the motor temperature...motors running at their limits can get very hot. Even hot enough to melt plastic mounts.