[rootboy]

I just got my new G540 wired up today (the Z axis anyways), and I decided to try it out to get the direction of the stepper right before soldering it up.

Using LinuxCNC, and using the G540 defaults that come with it, my motor would stall out about half of the time and turn very slowly otherwise.

The mill is a Zen Toolworks with the NEMA 23 motors. Here are the specs on the motors:


Model # : 57BYGH41-401
Resolution/Step Angle : 1.8°
Phases : 2
RPM : 3000
Voltage : 3.64VDC
Amperage : 1.5A
Leads (Wires) : 4 Leads
Phase Current : 0.4A
Winding Resistance : 2.7 Ohm
Inductance : 5.6 mH
Holding Torque : 69 oz/in. | 5.0 kgf/cm


Wiring Details

Four wires with the following color pattern:
Red : Phase A (A+)
Blue : Phrase A Return (A-)
Green : Phase B (B+)
Black : Phase B Return (B-)

For my current sense resistors, I chose 390 ohm resistors (the math specs 400 ohms, so I should be good). I have a 24 VDC 15A Regulated Switching Power supply. Not sure how clean it is, but it worked fine with my old Chinese setup on the same mill.

I decided to switch to the G540 since the Chinese gear I had was nothing but a PITA. However, it was working so I know that my motors and my power supply are fine.

I haven't tweaked the trim pots (AKA Gecko Volume Control), since I figured that it should run regardless of that setting.

I chose 400 ohms based on phase current, was I supposed to use the 1.5A rating instead? (meaning replace the 400 ohm resistors with 1.5k ones).

Call me crazy, but I used RadioShack S-video High Flex Dual Zip Cable (part #278-0470) to connect the motors. It's high flex, so it will last foreve. And by using the shields as conductors, as well as the core, I get four decent sized wires for my motors. I used about 6 feet for each motor cable.

I *do* have my config file somewhat screwed up, but I was just after direction anyways. Right now I'm concerned about the lack of torque.

Any thoughts?

Thanks!

[LeeWay]

I think your PS is too low. You won't get much torque on 24 VDC. Speed either.

Most guys run the 540 with a 48 VDC PS. Your motors are rated north of 75 volts.

The resistor should be whatever they suggest for 1.5 A. Getting it right on the money here will help too.

[Crevice Reamer]

I concur. You are strangling the motors. With the 400 Ohm resistors, the motors will only put out about 18 oz torque. With 48V, they will run twice as fast.

Get these resistors, (Might as well buy 10 for 82 cents.) USPS shipping will cost about $3 and take 2 days:
MFR-25FBF-52-1K50 Yageo | 1.50KXBK-ND | DigiKey

And this PSU:
High-Torque Stepper Motor, Stepper Motor, Driver, Stepper Motor kit, DC Servo Motor, DC Servo Motor kit, Stepper Motor Power Supply, CNC Router, Spindle, and other Components. Automation Technology Inc

CR.

[rootboy]

Holy crap! I just did the math on my 5.6 mH motors, and you're right, a 48VDC PS is called for.

Jeez, why don't I just plug it into the wall socket...


But it ended up being the resistors.

I cranked my 24VDC PS up to 29 volts (as far as it would go), and there didn't seem to be any improvement at all.

So... not having a 48VDC PS handy, I did the next best thing, I put my 12VDC PS in series with the "29VDC" PS (checking to be sure that neither of the power supplies were grounded to the output). This gave me 41VDC, and it still made little difference.

So I then took out the resistor, and it ran perfectly (back at the 29 volts with the other PS disconnected - I'm not that crazy...).

It didn't take long, but the stepper got pretty hot, but I figured that this was coming, so I checked for heat often.

I then cobbled up a couple of resistors to get ~1500 ohms and it works beautifully!


Thanks so much guys!

[rootboy]

I concur. You are strangling the motors. With the 400 Ohm resistors, the motors will only put out about 18 oz torque. With 48V, they will run twice as fast.

Yeah, silly me. I thought that when they specc'ed "Phase Current" they meant Phase Current.

Get these resistors, (Might as well buy 10 for 82 cents.) USPS shipping will cost about $3 and take 2 days:
MFR-25FBF-52-1K50 Yageo | 1.50KXBK-ND | DigiKey

Thanks! I buy from Digi quite often, so I'll be able to roll it into some other purchase.

And this PSU:
High-Torque Stepper Motor, Stepper Motor, Driver, Stepper Motor kit, DC Servo Motor, DC Servo Motor kit, Stepper Motor Power Supply, CNC Router, Spindle, and other Components. Automation Technology Inc

CR.

I had searched all of for the best deal on a 48VDC PS, and this is better than what I could find!

Thanks again!