[dinkyguitar]

Hi All,

I saw this setup on ebay:

Gecko G540 w/ Three Nema 23 Steppers 620 oz/in motors | eBay

Most of the G540 kits I saw have 381oz-in motors w/ 4 wires.

The ebay kit has 620oz-in motors w/ 8 wires.

How do you wires motors with 8 wires, and is this kit better than the kit with 381oz-in motors?

dinky,

[Dylwad]

Inductance looks high on those motors, do the math on geckos site to see what voltage they should be run at and ill bet its over the 50volt max of the 540.

8 wire can be run in series or parallel, still end up with only 4 wires connected to the driver. Wiring schematics are on geckos site too.

Ill bet the 381oz motors have more torque at speed than the 620's at 48 volts.

[awerby]

But that doesn't mean they're necessarily better for your purposes than motors that have less. Holding torque is a good thing when the motors aren't moving, but the higher inductance that goes with it means that they're less responsive than motors with lower inductance, given the same voltages. The rule for steppers it that they perform best when given a voltage equal to the square root of their inductance times 32. So in this case, the inductance is 6.4, so the square root's about 2.5, times 32, so it wants 80 volts. Since the G540 maxes out at 50v, this doesn't sound like a good match to me, although these motors would likely work better with some of the other Gecko drives, like the G203V.

8 wire motors can be wired series or parallel. But wiring them in series sends the inductance through the roof. You wire them parallel by feeding two coils power at the same time, alternating between one set and the other. This is generally recommended for best performance. Here's a diagram from the Keling site that lays it out (although the wire colors may differ from the ones in that ad): http://kelinginc.net/KL23H286-20-08B.pdf

Andrew Werby
www.computersculpture.com

[ger21]

For best performance, motors need to be matched to the design of the machine, specifically the drive method.
If you design your machine so that the steppers never spin faster than maybe 300-400rpm, then the 620oz motors might be a better choice.
If you need the steppers to spin at 1000rpm, then the smaller motor is definitely a better choice.

[dinkyguitar]

Thanks guys,

Very technical explainations but I think I understand....I'll probably go with my gut and stick with the G540 w/ 381oz-in motors from Keling....in addition, getting an e stop, 3 limit switches, and extra motor wires for soldering and making them longer.

dinky