New setup, can't move A4988 steppers.

Hello,
I have a new setup, that I will be controlling a Shapeoko CNC. I am using A4988 steppers from Pololu. I got the port to work using the port tester, and see that the inputs and outputs work, but I cannot get a motor to move. When I hit F2, the motors vibrate once per second, but that is it. For the driver config I have Step Time and Step Space = 1000, and Direction Hold/Setup = 200000. Any ideas? How can I debug this?
Thanks,
CP

Probably need more information about how you are set up and what you are doing.
Type of breakout board, stepper driver, pins you used in setup etc.

With the power on are the steppers hard to turn by hand?

Did you use and did it work with stepconf?

Rick G

If you really want this to work here are some questions that may get you going:

What step sequencing mode has been selected via MS1, MS2, and MS3?
(The right answer for this is anything but full step mode 1/2 or 1/4 being best)

What motor you are using? I'll take a link to the data sheet.

What are you using for your logic power supply?

What are you using for your motor power supply?

What setting is your reference trimmer at? full anti-clockwise being 1 and full clockwise being 10

Extra credit for measuring the current draw of the drive while you are operating it.

Is anything hooked up to ENABLE, RESET, or SLEEP?

What logic is ENABLE, RESET, and SLEEP? High or low.

Are you using any kind of isolation on your step and direction lines?
(the right answer here is I have an optically isolated BOB)

Do you have a filter capacitor on your motor power line? Allegro is calling it CIN2, a bulk capacitor. They specify a 100 uF but I would use something a bit bigger. 220-470 uF

These drives are not exactly plug them in and go. You need to have a few things right before they will work.

This is your driver isn't it?
www.pololu.com/catalog/product/1182

Oh, and you have met the minumum timing requirements but you might want to give yourself a bit of breathing room there, at least until you get up and running.

Thanks for the help. Going through your questions, I have found the main problem as I had the step and dir wires backwards. But I have a few questions about your questions.

1) For the breakout board, I am using a buildlog.net arudino stepper shield but standalone connecting to a DB25 breakout board, it does not have opto-isolation, how important is this? Note I am using a parport card, and not running from motherboard.
2) Although I can move the stepper now, there is a twitch at .5Hz. any idea what could cause this?
3) The BOB, has 47uF to motor power. Any comments?
4) Running latency test, I get worse case with a few glxgears going 25000ns. I currently have base thread time in stepconf to be 30000.


I am using www.phidgets.com/products.php?category=23&product_id=3308_0 for motors, and www.pololu.com/catalog/product/1182 for controllers.

Thanks

CptanPanic wrote:

Thanks for the help. Going through your questions, I have found the main problem as I had the step and dir wires backwards. But I have a few questions about your questions.

1) For the breakout board, I am using a buildlog.net arudino stepper shield but standalone connecting to a DB25 breakout board, it does not have opto-isolation, how important is this? Note I am using a parport card, and not running from motherboard.
2) Although I can move the stepper now, there is a twitch at .5Hz. any idea what could cause this?
3) The BOB, has 47uF to motor power. Any comments?
4) Running latency test, I get worse case with a few glxgears going 25000ns. I currently have base thread time in stepconf to be 30000.


I am using www.phidgets.com/products.php?category=23&product_id=3308_0 for motors, and www.pololu.com/catalog/product/1182 for controllers.

Thanks

You still haven't said how you've set the current for your motors. But without that information there are still some things I can think of to do to make your motor drivers work better.

1. Add capacitors to your power inputs on your motor drivers. What is on your drivers already is not nearly enough. I suggest 100-220uF where your motor power goes in on your driver boards and 10uF where the logic power enters your driver boards.

2. Optically isolate your control lines. This is best done at the motor drivers themselves. Although at the BOB is better than nothing I guess.

3. Increase your signal timing. You're right at the limit now. At least increase it until you've determined it is not a factor.

I've written a couple articles about how I built my setup and while not specifically applicable to you, you might still get some ideas of one way this stuff works:

www.instructables.com/id/Parallel-Port-Break-Out-Board-BOB/

www.instructables.com/id/TB6560-Microste...opper-Stepper-Motor/

If you're handy with electronics maybe you can adapt my optical isolation for your motor drivers. It works pretty good, if I do say so myself:



But fully understand it before you go hooking it up to your PC. It needs about 12 milliamperes to operate. Which is no small amount of current in the world of micro-electronics. There was a time when I didn't know I needed isolation myself.

img683.imageshack.us/img683/6498/stepproto1.jpg

That goofy little board with the 2 ICs on it is a daughterboard I had to make for one motor driver I made. This is the second of that type of driver I made, same circuit, different layout:

img697.imageshack.us/img697/7711/pict0789w.jpg

The white IC on the board is the optocoupler. You'll know if you need optical isolation when you run two motor drivers at once. If they go nuts then you need it. My money is on you'll need it too.

2) Although I can move the stepper now, there is a twitch at .5Hz. any idea what could cause this?

Not exactly sure what you are saying here by twitch. You will find that steppers have a tendency to vibrate at low speeds, with one particular rpm range much worse than others.
Again play around with the timing, check the amps are not set too high.
Glad to hear you are making progress.

Rick G

andypugh wrote:

CptanPanic wrote:

connecting to a DB25 breakout board, it does not have opto-isolation, how important is this?

I don't think it is crucial. I originally wired my drives direct to the parport, and then replaced the parport with a Mesa 7i43, and still have the drives wired direct to the header pins. It adds a bit of noise immunity and hardware protection, but at the expense of complexity and slight (and irrelevant) propagation delays. (and at the expense of expense). In the unlikely event that you damage the parport card, replacements are cheap.

What kind of drives were you using? Color me extremely interested.