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I need to find a inexpensive replacement stepper motor and I am wondering if all of the specs need to be matched or are there some that don't need to be exact.

Right now they are using a six wire motor, but only four of the wires are in use. The center wire on each side is cut off.

One of the motors is a Astrosyn 23LY-C205-03V

It is a .9 degree motor but if they are only using four wires does that change this spec? Can I get a 1.8 degree four wire?

Do I need to match resistance, voltage, inductance, and current? Or will it still work if they are close but not exact.

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I am wondering if all of the specs need to be matched or are there some that don't need to be exact.

It completely depends on the application. Unfortunately you don't give us enough information to provide you with a good answer. However, in general stepper motors are fairly standardized. If you get one with the same step size, and the same general shape and size, and you can wire it up correctly (since the driver uses 4 wires it's pretty easy to convert a 6 or 8 wire to 4 wire use) then you should be fine.

If the device that uses the stepper is using it near its limits in terms of speed, torque, etc then you may have problems if you don't match the winding impedance, mechanical resonance, etc. This is only a problem in high performance machines, though.

I would contact the manufacturer, if possible, and get their recommendation. If not, try a different motor out and see if it works. Chances are good it'll be fine.

The step size is independent of the wiring - a four wire stepper at 0.9 degrees per step is the same as a 6 wire and 8 wire, just the coils have taps in them (or separated). So you will need to match the step size regardless of the wiring.

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  • \$\begingroup\$ They won't release much info the system because they want us to buy the parts from them at a high price. They are mostly from Coin op redemption games. I see the same sized motor used on a few different games. If I understand you correctly, I will try one that is a .9 degree six wire the same size and try and get as close as I can with the other specs and give that a try. Thanks \$\endgroup\$ – user2579 Jan 12 '11 at 5:56
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Ideally if you replace one you should also do the other. And no you can't as that means the 0.9 degree stepper motor will have to have two pulses to catch up with the 1.8 degree one. Yes you should try to match voltage, resistance and current. They sound as if they are using them in bipolar mode.

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  • \$\begingroup\$ One follow up to this, If I am using a 1 amp Stepper motor and replace it with a 3 amp. Will the 3 amp draw that much current and therefore stress the driver circuit or will the 1amp circuit only draw one amp from the 3 amp motor? Or is it OK to replace a 1amp with a 3amp motor? Thank you for the help. \$\endgroup\$ – user2579 Jan 21 '11 at 23:43
  • \$\begingroup\$ Yes if you are using a 3A stepper motor you need something that can handle that current. For my project involving stepper motors I'm using a ULN2803A to drive them and each darlington pair can handle about 1/2 an Amp so double up if you need more current. As for swapping the 1 amp with a 3 I'm unsure on that. Can your power supply handle that? \$\endgroup\$ – Dean Jan 21 '11 at 23:46
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If you use the 1A driver circuit for a 3A stepper motor, it will definitely affect the driver circuit components.

But if you run it with a battery which can supply a maximum current of 1A, then it wont affect the driver, at the same time you cannot get the maximum torque.

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