I have 3 stepper motors I bought on ebay. The seller thought they were Nema 23 motors. They have the identical dimensions of a Nema 23 280 ounce*inch motor. They have 4 wires that are Red, black, green, and white. The red and black are electrically connected, and white and green are electrically connected.
The Nema 23 documentation says the 4 colors should be red, black, orange, and yellow. Does anyone know which of my four motor wires are A+, A-, B+, and B-?
I finished mounting the 3 motors, and I have a Gecko g540, and a Keling 48v 7.3amp power supply. I'm ready to start connecting wires! ya! If I guess wrong, is it bad to connect the wires like:
B-, B+, A+, A-. will anything break? or will the motor just run backwards or something?
You should be able to swap A with B and nothing bad will happen. So just wire up red & black to the A outputs, green and white to the B outputs. If the motor runs backwards you can easily swap over any 2 wires from the same output pair - e.g. red and black.
OK, I finished wiring everything. I tried it out and the G540 won't come out of fault mode. I followed the directions here:
I was pretty meticulous. Are there any suggestions on how to get it out of fault mode?
This version of the Gecko drive has a charge pump switch, and I have it turned ON. When I turn the charge pump switch off, the fault mode shuts off, and then there is just the green POWER LED is on.
Mach3 says that there is an emergency switch issue.
Sounds like you need to enable the charge pump feature of mach3. Don't ask me how, I haven't got around to running it yet!
Edit: does mach3 think you have an e-stop switch fitted? If so, I think this might need to be disabled, it might be preventing mach3 from generating the charge pump signal. I think the e-stop should be directly connected to the G540, mach3 doesn't need to know about it. Can you connect something to pin 16 of the DB25 and see if you are getting a charge pump signal (> 10 KHz)?
OK, I got it working, but I think the motors are too small for my table. I don't really know the torque rating, because I don' tknow much about them, but now the problem is that it stalls and goes in and out of moving sort of. it turns very smoothly when I hold the motor in my hand. I'm able to make it behave like it does on the table when I try to keep it from turning. Here's what I have right now:
Gecko G540, Keling 48v 7.3 amp power supply (I think it's 7.3). I'm going to buy new motors on Monday. I might even buy a bigger power supply if I have to, but the Gecko can only handle motor coil amps up to 3.5 I think.
What's the biggest possible Nema 23 motor I can get that the Gecko can handle?
Numb Nut, that was it exactly! Thank you!
Last edited by MPaulHolmes; 08-08-2009 at 11:45 PM.
Try lowering the acceleration and velocity for a particular axis, and see if that helps the problem. You may just be trying to push the motors harder than they are able to cope with.
You don't say what kind of mill you are hooking this all to, what kind of screws, reductions, or other data that may be relevant.
Good point. OK it's a Harbor Freight geared head mill:
I'm doing no reduction:
All I know is that 1 revolution of the cranks corresponds to 0.1 inch of movement.
Perhaps another thing to check might be your current set resistors...?
Assume you have tried spinning the ballscrews by hand to check that they aren't binding and that the gibs are neatly adjusted (and aren't locked!)...
I'd try it like how escott76 has suggested - try running the motor at a very slow speed (low velocity and low acceleration) - forward it a few turns (e.g. a multiple of 2000 steps) and measure the rotor movement. To measure rotor movement you could just eye ball it (missed steps will be multiples of 1.8 degrees***) or use a small piece of mirror, some hot glue, a laser and a surface at few feet away. Checking rotor movement rather than table travel might seem elaborate but eliminates the effects of table backlash.
Repeat this while increasing the max speed setting until it starts to lose steps. Then back off the maximum speed to a safe amount and start working on the acceleration setting in the same way.
Disclaimer - if I had a CNC mill then that is how I'd do it...
***Edit: this is wrong - missed steps would cause a rotor position error that is multiples of 4x step angle, thus 7.2 degrees. You can eyeball that, no need for laser and mirror! See accuracy and resolution section of http://www.geckodrive.com/upload/Step_motor_basics.pdf.
Last edited by Numb Nut; 08-11-2009 at 05:27 AM.
Again, I'm not saying your motors aren't up to the task. They may well not be, but simply bolting on a "bigger" one may not solve the problem. You want to match stepper voltage to the power supply as closely as possible. 32 times the square root of the inductance will give you the correct operating voltage for a motor. You want to stay as close to that as you can for best operation.
Buying motors from Ebay with no idea what their specs are can be problematic, as you have no information to go by and you can't make informed choices about the correct thing to do. Don't mean to pick on you, but for others reading, it's not always cheap to buy cheap there.
you are right, escott. Is the optimal voltage related to the torque at all or just speed? One motor I was looking at is 495 ounce*inch but It's optimal voltage is 84. The gecko can go to 50v. Would torque suffer at 50v, or only speed? Maybe the current wouldn't be able to get all the way up since the inductance would make the voltage change so slowly, and then it would already be to the next step?
The motor posts I have are like 0.31" in diameter, which isn't even an option for the Nema23 motors that I have seen. I wonder of they are a cheap knockoff.
I'm using the stock screws on the mill.