Motor Current

Discussions related to the Rostock MAX v2
Post Reply
klarson18
Plasticator
Posts: 6
Joined: Sat Mar 12, 2016 9:58 pm

Motor Current

Post by klarson18 »

Is there a chart that shows the motor current output for the different numbers in the configuration?

Stock MaxV2

I am wanting to use a different extruder motor with lower current, and trying to find a chart for the settings.

Ail
Prints-a-lot
Posts: 34
Joined: Tue Jan 05, 2016 11:40 am

Re: Motor Current

Post by Ail »

Not sure there is a chart. To be the most accurate you would probably have to hook up a meter and test. There are two references in the firmware but not sure if that helps you or not.
(RAMBO 135 = ~0.75A, 185 = ~1A)
Also, Cut / paste of Rambo stepper info if you want to do math.

The current for the stepper motors is set by firmware controlling the 8-bit digital potentiometer. For the end user this is seamless. The firmware sets the current at every boot and The following formula from the Allegro datasheet describes how to set the reference voltage: ITripMAX = VREF/(8 X RS). RS, the value of the sense resistor on RAMBo is equal to 0.1Ω. ITripMAX is the current the stepper motors are rated for. Ideally you should start with 70%-90% of maximum. You can verify the voltage for each driver by plugging the reference voltage (VREF) measured at the X_REF test point (Y_REF,etc for the other drivers) in the following formula:
VRef = ITripMAX * 0.8
Note the A4982 is set to be limited to 2A. This means the adjustable voltage range is 0 to 1.66 volts. The following formula will yield the 8-bit binary value, Wv, to be entered into firmware or directly over SPI.
Wv = (VRef / 1.66) * 255

User avatar
Tincho85
Printmaster!
Posts: 659
Joined: Sun Nov 03, 2013 12:27 pm
Location: Buenos Aires, Argentina

Re: Motor Current

Post by Tincho85 »

Under Configuration.h check for this input:

#define MOTOR_CURRENT {175,175,175,135,0} // Values 0-255 (RAMBO 135 = ~0.75A, 185 = ~1A)

The array of settings is {X,Y,Z,E0,E1} So for the extruder you must change the E0 number.
Note tha I have the old Wantai motors and a planetary geared for the extruder, so those values should be different from current Rostock Max versions.
Martín S.

Post Reply

Return to “Rostock MAX v2”