A3977 Board buy if interested

[pminmo]

hi there,
I'm new to the forums, i've searched a lot in the forums and i couldn't find anything related. I want to ask if trip current of the motor can be changed with a3977 ic on the fly. I want to use this card with a simple modification, i will connect a digital potentiometer and i want to raise the motor to the peak current whenever it will rotate. Else i want to lower the current for not to heat the motor excessively but also obtain a slight braking from the motor. If anybody tried to change the trip current on the fly please let me know.

You can modify Vref to alter motor current. I can't say I would recommend doing it while the motor is actually rotating though.

[synchron]

I've finally constructed my prototype model and now I am experimenting on it. As I mentioned before I was planning to set the current with a digital potentiometer and that also worked fine but there is only a single problem, at idle state motor creates very high pitched weird sounds in every single mode(full, half, 4x, 8x). First I thought maybe digital pot gives an oscillating output and I got rid of it and placed a good old trim-pot with 0.1uF decoupling capacitor at its output. But again these sounds continued, then I tried to measure what is going on with oscilloscope placing the probe on sense connection of the IC (since it is the sense port of chopper circuit where you can see the actual waveform). And the results are interesting, in idle mode there are lots of pikes and while rotating there is something going on in microstepping modes but I would not say that a sinusoidal. I am thinking of PWM timer R, C values might not suit my motor. Any other ideas?. By the way I am using a Lin Engineering 5718M-02S 24V 2.1A motor.

[synchron]

I nearly forgot. I thought that this IC has the capability of 2.5A per phase but now I am only seeing max 1.0A. Did I read the datasheet wrongly?

[pminmo]

Your hearing the frequencies of the choppers running, its normal. You can tweak the rc1 and rc2 values to help with certain motors. With a machine actually running and cutting, you don't hear them. If the machine is paused for long periods of time, the motors should be disabled anyway for safety.

You can't measure the current with normal test equipment.

[synchron]

Your hearing the frequencies of the choppers running, its normal. You can tweak the rc1 and rc2 values to help with certain motors. With a machine actually running and cutting, you don't hear them. If the machine is paused for long periods of time, the motors should be disabled anyway for safety.

You can't measure the current with normal test equipment.

Thanks for the chopper advice. I tried with 640pF, 1000pF caps with 20Kohm, 30Kohm, 50Kohm, 100Kohm resistors in all combinations but I still hear buzzes with varying frequencies depending on at which microstep level the motor is stopped. If I am hearing frequencies; what should I do, lower RC multiplication or increase? In data sheet it is stated as to set RC multip. to determine fixed off time, and I think ic changes on time and induces PWM current control on the motor so chopper frequency is changing at all times with the formulation fpwm=1/(ton+toff). I think thats why I could not set an appropriate RC multip. for my motor. On the other hand, how should I set C to obtain a proper blanking time.

[pminmo]

Thanks for the chopper advice. I tried with 640pF, 1000pF caps with 20Kohm, 30Kohm, 50Kohm, 100Kohm resistors in all combinations but I still hear buzzes with varying frequencies depending on at which microstep level the motor is stopped. If I am hearing frequencies; what should I do, lower RC multiplication or increase? In data sheet it is stated as to set RC multip. to determine fixed off time, and I think ic changes on time and induces PWM current control on the motor so chopper frequency is changing at all times with the formulation fpwm=1/(ton+toff). I think thats why I could not set an appropriate RC multip. for my motor. On the other hand, how should I set C to obtain a proper blanking time.

You can't get rid of the noise.

[pminmo]

Maybe is A3977 not fitable for your motor?
Someone recommend a new chip THB6064AH to our company.I have looked through the datasheet from google http://www.hhbytech.com/Admin/Media/...445_588784.pdf .It sounds much better than A3977.

Hope it's useful for you.

In general, most monolythic stepper ICs will generate spurious motor noise when setting idle. It's the current control oscillators of the choppers.

As to the Toshiba parts, they have the same tendancy, although not quite as bad as the 3977.

I'm always amused at the noise issue, you never hear the noise over a running spindle motor. When idle the motors should be disabled for safety reasons, thus it's a non issue unless your using a laser.