I have a Nema 17 unipolar stepper motor from OMC-SteppersOnline.com. I'm trying to determine the center taps for the two coils. I tried to determine
these using my sensitive ohm meter with no luck. All wire-to-wire readings for a given coil are 0.0 ohms.
Could someone please tell me how to do this.
PS: Wire colors: red, white, blue for coil 1, and black, green, yellow for coil 2,
[Edited on 18-12-2017 by Magpie]aga - 18-12-2017 at 07:21
Yellow and white are the centre taps according to the spec sheet.
It also specifies 38 ohms per phase, so something sounds strange with your 0 ohm readings.
[Edited on 18-12-2017 by aga]Magpie - 18-12-2017 at 08:10
Thanks so much aga. I also have written to SteppersOnline. Maybe they can explain my strange readings.aga - 18-12-2017 at 09:22
Try measuring a known resistance to see if the meter has gone crazy.Sulaiman - 18-12-2017 at 11:01
you can measure the ac voltage produced when you spin the shaft,
that will easily identify the centre tapMagpie - 18-12-2017 at 12:43
I have two volt-ohm meters, an old Heathkit and a new Radioshack. The Radioshack is giving 250Ω to the center tap and 300Ω coil end to coil end.
So at least I'm showing resistances in the right proportion even if the center tap resistances should be only half of that shown for coil end to coil
end. This is the same for both coils.
I'm getting the motor to bump when I apply 24v through the a4988 driver. But I can't get it to run. I have switched the wires around to try to get
it to run. Any suggestions will be appreciated.aga - 18-12-2017 at 15:15
eeeek ! It's a 12V motor !
You are either being obtuse, trying to destroy the motor, or simply refusing to look at the spec sheet.
The grid at bottom-right clearly shows how to run it.
Edit:
The blanks are -ve for clarity.
Only the + is shown in case of a printing error.
[Edited on 18-12-2017 by aga]Twospoons - 18-12-2017 at 15:36
He's using a current controlled stepper driver chip - 24V wont hurt - just means you can ramp the current in the windings faster, and therefore step
faster before losing sync.
I take it you have set the current to ~300mA?
It is of course possible you have a stuffed motor - those resistance readings are weird.
[Edited on 18-12-2017 by Twospoons]Magpie - 18-12-2017 at 17:12
The grid at bottom-right clearly shows how to run it.
I'm being obtuse. Thank you for pointing out that grid.
The minimum voltage of my power supply is 24vdc. I was wondering if I have damaged anything, like the driver. I could use my 12vdc battery charger
as a power source.
I'm not controlling or limiting the current. I do have that capability, however.
edit: I tried the 12vdc supply - no change.
[Edited on 19-12-2017 by Magpie]Magpie - 20-12-2017 at 20:50
I am working on a circuit for a Nema 23 stepper motor as well as a Nema 17 stepper motor. The problem I have with the Nema 23 is that I don't have a
controller and they cost nearly $400. That for the Nema 17 is just a few dollars.
I have written to Varmint for help but I'm not sure he visits this board much anymore. So I submit a copy of this letter to you for any help you can
give:
"I have a Nema 23 Orientalmotor stepper motor that I plan to use to drive an overhead mixer. The motor is PKP296D45AA and the driver is CVD245BR-K. I
need a controller so that I can use it to set the rpm of the mixer. In talking with Orientalmotor they say a SCX11 controller is available. But this
will require programming and cost nearly $400.
Do you know if there is a cheaper, simpler way to control this motor? Any help will be deeply appreciated.
Don" aga - 20-12-2017 at 22:54
That SCX11 controller looks very capable and has many options you would never use, hence the high price.
I have 3 of those and they were easy to get going.
Wire EN-, CW- and CLK- to 0v.
Wire EN+ to 5v.
Wire CW+ to either 5v or 0v depending on which rotation direction you want.
The A+/-, B+/-, O+/- match up with the wire colours specified on the spec sheet for the motor.
Provide pulses to CLK+. Each pulse will produce 1 step on the motor.
Cost (for both) around $14 from ebay.Twospoons - 21-12-2017 at 14:05
If you wanted to go just a little more sophisticated than a 555, then one of the small Arduino MCU boards would be a simple way to add programability
- maybe for adding a run timer, or an rpm display.Magpie - 21-12-2017 at 20:37
Thank you both for your help. I've been getting ready to go duck hunting and haven't had time to evaluate your responses. I should get to them
tomorrow.
