A4988 board..GUYS KINDLY HELP ME

I am using A4988 driver board to control stepper motor. The scenario is i need to connect two motors driven by 2 boards to a single source and test its running.

when each motor is tested separately for 24 v, it runs properly without ay heating issues. But when two motors are connected and when step is given to motor A, motor B gets heated and the board is damaged { condition required is While A runs B should not } But what happens is while A runs B gets some current and overheating. I will attach the specifiactions in the following threads... please help me to get rid of this problem

... sounds like improper wiring ...

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Can tell me how to calculate the current which is delivering by A4988 stepper driver

please find my details are

RS = 0.05
R1 = 20K
trimpot value =20K
VDD =5 volts


I want to operate motor of 2v and 0.45amps

You can google "a4988 datasheet" and download the pdf and at page 9 it is written:

I TripMAX = V REF / ( 8 x R S )

Which means the max current (peak current or I trip current) is given by voltage on REF pin divided by Rs multiplied with 8. Further if you look at the schematic on pololu page you see that REF pin has a pullup resistor followed by a potentiometer. Basically that potentiometer on the carrier driver it is a voltage divider and playing with the potentiometer means the voltage on REF pin changes. That is what the potentiometer does and how the I trip max current is set.

So you need to take a multimeter and measure that voltage on REF pin, voltage named VREF. Modifying the potentiometer position will change the VREF voltage setting. If you can set that voltage to VREF = 0.18V, and you have RS=0.05ohms, then it will give I TripMax = 0.18 / (8x0.05) = 0.45A max. Given that your motor maximum is 0.45A and that perhaps the multimter also has an error especially at low values, then 0.16-0.18 or something like that should be your max setting, which is probably low, but thats what the math says.

Your motor with a 0.45A max is not ideal imo. If your motor would of had like a 1-1.5A max, then probably you could of afford a setting like 0.8A or so, which would of been different. With 0.45A max probably your going to have trouble with the torque and the motors will probably run quite hot.

Thnak you so much for your valuable info @Noobman

Edited 1 time(s). Last edit at 10/01/2014 08:39AM by arun.

Quote
arun
I want to operate motor of 2v and 0.45amps

How did you come up with those numbers? Are they from the spec sheet from the steppers? If so, the voltage given there is just a computed value based on the resistance and current requirements. It doesn't really have any useful meaning with regards to operating the steppers as you actually usually want the voltage to run higher for more rapid current rise time.

And as NoobMan indicated, .45 amps is a pretty low current requirement. You don't say what you're using the steppers for or what size they are, but for 3D printing related tasks that's a pretty weak motor that is likely to stall or miss steps if there's anything more than minimal resistance to movement (aka load).