lower the amperage on steppers?
October 11, 2012 03:08PM
Hello everybody!

I have a couple of questions.
I have some steppers and I can't find the datasheet, even from the manufacturer. Maybe the motors are a little old (although mine are new).

The label says:

PAS STEP: 1.8° R: 0.7Ω
U/Ph: 1.68V

They looks like a NEMA23, but slightly different. The "front" is 56x56mm, 47x47mm between holes; depth is 40mm. The shaft is 19mm long, 6mm diameter. I am attaching a couple of pictures for reference.

do anyone have any information on these motors?

The other thing is that they are 1.68V and 0.7 Ohms per coil, which would give 2.4A.

I think that 2.4A is a little too much for RAMPS+Pololu, so I was thinking if it's possible to add a 0.5 Ohm resistor in series with the motor winding,
to get something like this: 1.68V / (0.7R + 0.5R) = 1.4A

will this work?
I'm assuming that probably will lost some torque, but I think that these motors have more that enough.


Edited 1 time(s). Last edit at 10/11/2012 04:14PM by Biomech.
Re: lower the amperage on steppers?
October 11, 2012 07:46PM
No serial resistor needed. The current limiting built into the usual stepper driver chips should work just fine. Ans yes, lower current means lower tourque.

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Re: lower the amperage on steppers?
October 12, 2012 04:11PM
I was reading about this situation with these kind of motors. I think that maybe is necessary to apply this mod

I need to have this clear before deciding to buy RAMPS + Pololu or start thinking in other option for electronics.

Re: lower the amperage on steppers?
December 07, 2013 05:42PM
Im watching those Steppers on ebay for a while, but where did you get the the current of 2.4A a coil?
Re: lower the amperage on steppers?
December 08, 2013 04:16PM
The steppers are labeled with a voltage and a resistance. Ohms law will give you the current. In this case I = E/R ( 1.68V / 0.7ohms = 2.4A).

Those are small body steppers. One would *guess* that that are low torque running at full current. They may (or may not) be up to delivering enough torque for normal printer tasks when run off normal drivers. "Real" steppers (reasonable current and torque) are only $10 to $15. They are not the big cost in building a printer.
Re: lower the amperage on steppers?
December 12, 2013 07:46PM
Actually you're right, but the calculation seems not to match in each case. I hope you ain't right about the torque, because i bought 3pcs a few minutes ago winking smiley. I have already a problem with low torque on my nema23, therefore i bought these ones, and I let you know how they are winking smiley

Edit: My fault. The slightly torque was attributed to a loose gearwheel on the motor shaft . A drop superglue fixed it, thank god!

Edited 2 time(s). Last edit at 12/13/2013 11:39AM by dommi81.
Re: lower the amperage on steppers?
December 21, 2013 06:04PM
Okay, I got the mentioned stepper motors and have them tested. The resultwas that my TB6560 shuts down every second due to overload. The torque was so bad that I could turn the shaft (at 2.3 A) with my hand.

Summary: Stay away!
Re: lower the amperage on steppers?
December 21, 2013 07:51PM
That's what I keep telling people. Avoid high current stepper if you are running these light weight drivers !!!!
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