Noisy stepper motor driver

While trying to adjust my v1.2 stepper motor drivers for minimum power use (not just to use less power, but also to stop them from overheating when idle), I noticed that they gave off various kinds of noise at the most promising settings. Depending on the setting, it could be a high-pitched whine, a hissing noise or even a sound like a deflating tire (http://www.youtube.com/watch?v=6VP2qARfJ7E). What is this noise, and is it harmful or just annoying?

Thanks,
-Lars

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[repstrapdk.blogspot.com]

When you reduce the current the circuit starts chopping. Normally the chopping frequency is ultrasonic so all you hear is a hiss. Sometimes you can get beating between two drivers that is in the audio range.

From the photo it looks like you have used wire wound sense resistors. They are not recommend as they have some inductance, which can cause instability. It is possible they are contributing to the noise.

I don't think the noise will cause any problems.

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[www.hydraraptor.blogspot.com]

Yes, I noticed when I got them that they looked significantly different from the ones. They were actually rather annoying as they nearly collide with the heat sink. I don't suppose them getting heating can be a problem?

It's frustrating to see the drivers using power on heating the heatsink when the motor is idle. Is there a way around that? Does the 3rd gen electronics avoid that?

Thanks
-Lars

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[repstrapdk.blogspot.com]

No I don't think heating the power resistors would be much of a problem as they are designed to run at high temperatures.

What the drives so when stationary depends on the enable lines. I think it is normal to power down Z and leave X and Y powered on a machine with belt driven X & Y, screw driven Z.

On gen2 I think the Arduino version has no enable control and the Sanguino has one enable for Z and another for X & Y.

I think gen3 has separate control of each enable line so it is up to the firmware.

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[www.hydraraptor.blogspot.com]

I've got something very similar, but with my Mendel extruder motor. I'm using Kymberly Andrus' controller, and a Zapp Automation 1684A on Wade's Geared Nema 17 Extruder, and get a incredibly annoying whine. I'd be really interested in any way to suppress this. I understand why it might be happening, but I'm not an electrical engineer and have no good idea where to start to tackle it. It is a REAL problem for me as the sound sets my spouse's teeth on edge

I should note that I have the d9/d10 cable in (correctly), as well as the rs485. Both have been moved away from everything else to minimize interference. That was definitely not the problem. I've also tried adjusting the 10K POT, and I can find spots where it helps, but mostly they are too high or two low in terms of current and the motor either doesn't step at all or stalls.

To my untrained ear, I would guess that the sound varies in the range of 2000-5000 Hz and varies in amplitude as well (from "uh oh, there's a mosquito in here" to "is the alarm clock going off behind me?".

I'm in the commissioning phase now - "first squiggle" tonight, in fact. The odd hiccup here and there, but overall the build and programming has gone pretty well. Hoping to make my first test part sometime in the next couple of days. If anyone has any ideas about how to get rid of the whine, I'd be very grateful!

If the noise is caused by the current chopper, then reducing the supply voltage from 12 V to 5 V might help by reducing the frequency. This will reduce the maximum speed as well.

I've also noticed that after I got through the commissioning phase and started running my stepper motors faster, they got quieter.

Finally, put a heavy table cloth or blanket between the table and the machine. I'm surprised how much noise is caused by vibrations transmitted into the table.

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Darwin clone, Gen 2 electronics, Arduino Duemilanove w/ AtMega328, 5D Firmware, Pinchwheel extruder
[www.codeerrors.com]

BobH - the noise, assuming your extruder controller is running the 5d Extruder firmware, is the 1 kHz PWM base frequency. You can change it to 64 kHz by adding the following line to your void setup() function in extruder.pde:

// Change the frequency of Timer 0 so that PWM on pins H1E and H2E goes at
// a very high frequency (64kHz see:
// [tzechienchu.typepad.com])

TCCR0B &= ~(0x07);
TCCR0B |= 1;

Be aware that it changes the timing on the extruder controller, but it doesn't seem to matter much in the limited testing I did. No guarantees though.

Wade

There is a very niosy voice in the three axis when I run a program but when I run it manually it is very smooth. I am connecting 2 motors of X-axis to the same point 2 & 3 in the breakout board to get the order at the same time, is it correct?

Thanks
Adel Aziz