I just received my EasyDriver v3 and would like to run an 8-wire stepper I have. I don’t have any documentation on the stepper besides what is on the motor, 12v 2w. Can someone give me some guidance as to how to figure out what wire is what and how to connect it to the ED?
Thank you for any help you can give.
Tron
TronCarter,
You need to ohm out the phase coils on the stepper motor to figure out which wires you need to connect together. You can find diagrams on many websites - search for bipolar 8 wire stepper or something similar. You’ll end up tying two ends of one set of coils together, and another two ends of the other two coils together, and then using the resulting 4 wires to go to the EasyDriver.
*Brian
Tron - There’s an image near the middle of this page that shows a typical 8-wire stepper:
http://www.usdigital.com/products/ms23c/
That might help clarify the setup for you - You can wire them in parallel or series. Parallel produces less inductance and will usually let you run it faster. I’m not sure how you go about figuring out which pairs correspond, or if coil polarity matters - I assume it does.
Jason
Thank you for the advice. I followed the instructions here:
http://www.piclist.com/techref/io/stepper/wires.htm
and found each of the halves of both windings “connected parallel-opposing”.
So, now I have four sets of two wires twisted together. How do I know which set goes where on the ED? Also, if it helps, there are two sets of four wires coming out of the motor so I assume each set of four corresponds to one coil.?
The ED doesn’t really care - Each coil gets wired to either the ‘leftmost 2’ or ‘rightmost 2’ coil connections on the ED - upper left 1-4 in this pic: http://www.sparkfun.com/commerce/images … 3-01-L.jpg
Polarity differences will just change the spin direction of the motor (I think - Brian will correct me if I’m wrong).
Jason
Jason,
You are %100 correct. Swapping the left two pins for the right two on the motor connector will make the motor spin the opposite direction. Swapping right two or left two will also do the same thing.
*Brian
Thanks, I will give it a try.
Tron
After following the instructions on the link I posted earlier, I hooked everything up this morning on my breadboard. I connected it to a Basic Stamp 2 for pulse and direction. No movement out of the motor. I checked everything with my multimeter and saw what I expected out of the stamp and ED, so I figured the problem was with the motor connections. I searched for a different set of instructions on how to figure out what is what with an 8-wire motor and came across:
http://www.bbastrodesigns.com/operate_s … dings.html
Near the bottom the section that starts with “Chris Rowland contributes the following:”
I was able to figure it out very quickly with my meter set for AC Amps. So, now I have my motor hooked up in series, tried it out and it works!! well, sort of. My program sets DIR high and pulses 1000 times, then pauses for 1 second, then sets DIR low and pulses 1000 times, pauses for 1 second and then starts over again. It does spin the motor for about 1 - 1.5 seconds in one direction, pauses for a second, and then spins in the other direction for 1-1.5 seconds. That part works great, but when it is supposed to be pausing, the motor pulses about 5-6 times per second. I thought that perhaps it was something that the stamp was doing, so I disconnected the pulse and dir jumpers all together and the motor continued to pulse 5-6 times per second. I tried adjusting the current pot from min to max and there was no difference. I have my bench power supply set to 11.8v for the motor that says 12v on the side. If it is connected in series, should I still supply 12v?
Anyone have any ideas?
Edit: It still does it at 6v and I noticed that with the stamp hooked up, during the pauses, it pulses in the last direction moved (as expected with the DIR pin still set).
TronCarter,
Strange. I’d do one more test - it is probably not a good idea to leave the STEP and DIR pins disconnected (they are just inputs after all and will float high and low, possibly causing your problem). Do this test to find out - take two 10K Ohm resistors, and place one between DIR and Ground and the other between STEP and Ground. Have nothing else connected to the STEP and DIR pins. Then turn on the motor power and see if you still get your ‘phantom’ pulses. Hopefully you will not. You can leave those resistors on when you connect up the BS if you want - see if they help.
I’m a bit confused about your question on the series power supply. Are you supplying 11.8v across the motor power pins on the ED? If so, then you’re doing it right. Also, make sure you have a common ground between the BS and the ED and the 12V Power supply.
See if any of those help solve your problem. If not, let us know and we’ll keep thinking.
*Brian
Tying the grounds together worked, thank you. It should also be noted that using the pull-down resistor on the STEP pin worked as well.
Next I have a question about torque for stepper motors. The motor has a gear on it which is supposed to spin a larger gear. The motor will run as expected when not installed, but when I install it and attempt to rotate the second gear, it just hums and doesn’t move. I don’t know whether the second gear has gained some resistance over the years of non use, or if the stepper is no longer turning with the same power.
This contraption was found on a shelf in the parts closet assembled, but with the wires just hanging loose from the stepper, so I am assuming that it worked at some point, but it seems that someone removed the controller long ago.
I am wondering if the way that I am wiring the stepper (in series) has reduced the amount of torque that I can apply. I have tried adjusting the pot on the ED without luck.
TronCarter,
OK, good, now I understand about the series question. The amount of torque change you get wiring it one way vs. the other is minimal - I think the only time you’d really need to care is if you are spending a lot of $$$ on your system and you want to maximize the torque at the speed that you know your system will run at (like certain CNC applications).
About the torque - If turning the pot (slowly) as your ED is running doesn’t change the way that the motor operates, then that means that the resistance of the motor is high enough (and your input voltage low enough) that the motor is self-limiting the current. In other word, the ED is not getting a chance to do any chopping (and thus no microstepping). While not really a bad thing, it just means that you are not using the ED to the fullest extent you could. With a different motor, you could probably get more torque.
Try raising the motor voltage (don’t go any higher than 30V). That will directly affect the torque. Can you easily stop just the raw shaft of the motor with your fingers? With the little motors I use I can’t. But when I put a gear on the motors I can easily stop it with my fingers. I’m not sure exactly what that means in terms of torque, but that’s the range that I get. The ED can only put out about 750mA/phase, and in your case it is putting out significantly less because of your motor. That’s not a whole lot - so don’t expect this system to put out too much torque.
*Brian
I cranked it up to 24v and it moved the second gear just fine. Since it is an 8-wire hooked in series, shouldn’t the voltage be doubled since I am now powering two coils with A+ and A- (and B+ and B-)?
Sure, but the ED can only deliver so much current through any coil. (750mA max) no matter what the voltage. Once your coil resistance (series or parallel - no matter - it’s what the ED ‘sees’ that matters) is low enough that it can max out the current at 750mA then it’s going to chop away and deliver the best torque.
I’m super glad that you got it to work!
*Brian
