Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: Quattro64 on January 29, 2009, 03:38:08 AM

Title: need help with steppers
Post by: Quattro64 on January 29, 2009, 03:38:08 AM
Hello, I have a homemade CNC machine with a controller I purchased a year ago from it is based on a geom mcu and is setup to control 3 axis. It came with its own mach 3 config. It's supposed to be plug and play ha. However when I purchased it I upgraded to the 200 oz in steppers, I basically have locked motors, they chirp and alternate between making noise and quieting down when I hit their axis jogs but they do not turn. The config they sent me seems to be ok but i don't know if they are wired correctly or maybe they are getting too much current. They have gone out of biz and I have to way to get direct support. They are 30v 3a 8 wire bipolar nema 23 200 oz steppers. I have read thru most of the posts here and have tried all the config and tuning steps ad naseum. I think I'm down to current and wiring. I just don't know how to troubleshoot this. thanks for any help.

Title: Re: need help with steppers
Post by: RICH on January 29, 2009, 06:51:06 AM
A number of things can cause problems.
Do you have documentation for your controller that you can post? 
The documentation should have information about current settings
and what is required.
Can you see how the wires are connected out of the motors? I assume you have a plug at the motor or controller?
Are the axis free to move without binding?

Go to the Gecko website and they have a turorial called "STEP MOTOR BASICS" and in that they have figures showing different motor connections. ie; 8 wire series or 8 wire parallel. This will show you how the wires are connected internaly in the stepper and you can check by measuring the continuity or resistance.

Got to go,
Title: Re: need help with steppers
Post by: Quattro64 on January 29, 2009, 10:48:44 AM
I did have it a while ago but as I recall it was scant. They mostly just gave me the videos and documentation from the mach 3 site. This unit is plug and play after all. I think what happened is the stepper upgrade I got didn't get reconfigured or wired properly in the controller or wired correctly for the motors. The unit usually comes with slightly weaker motors. What happens is when I jog the units come to life sort of they just dont move. So I have mach 3 set up fine and the configuration is getting to the steppers, they just don't turn. They do get hot and fast. Maybe they sent me the wrong motors for their config? or just wired them wrong? The controller unit consists of a controller board and power supply with inputs and outputs for the pc and motors. The Nemas are wired with red, green, brown and white each having their own separate lead and blue orange yellow and black grouped into a fifth lead. when the motors are active or with the motors detached would getting readings from the pins tell me anything? I saw a site that describes stepper motor wiring somewhere maybe that would help.

Title: Re: need help with steppers
Post by: Quattro64 on January 29, 2009, 10:51:12 AM
Thanks I will try the tutorial on the gecko website and post back, It might be a few days.
Title: Re: need help with steppers
Post by: Quattro64 on February 03, 2009, 12:45:22 AM
Ok on further investigation I found the wiring schematic for the keling kl23h276-30-8b motors online. It shows the various ways they chould be wired. It appears that they are wired either bipolar series or unipolar. And they miss-wired them. Currently they are wired up to a 5 pin female DIN socket plug, the black blue orange and yellow go to the center common pin and the others red green white and brown each go to their own pin which I assume corresponds to A+ A- B+ B- and the diagram shows that it should be Red that goes to common instead of Blue. Could it be that simple that they just got these backward when they wired these up at the factory? and switching the two wires on each motor will fix my problem! I'm such a newbie. Thanks for any replies.
Title: Re: need help with steppers
Post by: RICH on February 03, 2009, 01:53:14 PM
Attached is a motor wiring sketch. Please check double check current wiring. I can't recommend any particular wiring configuration
without knowing more about your drives / controller.

Title: Re: need help with steppers
Post by: Quattro64 on February 04, 2009, 02:49:53 PM
Thanks Rich,

I swapped the red wire for the blue wire as the diagrams suggested and this didn't change anything, tried all the various config and tuning steps in mach 3 and motors still get hot fast and are locked up. I think I am down to current coming from the controller that is causing the problem.  It appears that the unipolar wiring is what I have in place as stated above all the other wires are grouped together and according to my wiring chart they should be using 3 amps and 2.7 volts, how would I check to see what voltage is being passed from my controller using a dmm? If I am passing too much it would lockup my motors this way right? If so I could simply rewire them to another config that is more compatible with the voltage. I'd like to try this before I break down and buy different drivers to put in this controller box. all replies welcome
Title: Re: need help with steppers
Post by: Quattro64 on February 04, 2009, 05:56:24 PM
I took the controller apart and googled it. The board was built by Geom It is a pwm chopper driver board based on the sla7062m unipolar driver chip. It has three chips configured for the 5 din outputs. The controller comes with a switching powersupply that powers the board and supposedly puts out 4 amps to the steppers. Since this is a unipolar driver board it makes sense that the kl23h276-30--8b motors were wired for unipolar. But they were slightly miss-wired. I changed that and it didn't help these motors are specd for 3 amps in unipolar. Is the 4amp coming from the controller enough to lock them up and make them run insta hot? Could it be that one or both of the A or B phases are miss wired? I guess I can try every logical config now that I have the schematics for the motors and see if I can get these things to turn in unipolar config. I'll post back what I figure out.
Title: Re: need help with steppers
Post by: RICH on February 04, 2009, 07:06:03 PM
I ,nor anyone else ( unless they are familar with that particular controller ), can help you without info on the driver board.The motors should not get "hot". There must be jumpers or somethinig on the board such that you can change current settings if necessary.

If connected wrong you can blow a drive or worse.

Can you post a picture of the inside of the controller / board? Are there any markings on the board?

If you can at least post that info maybe we help out.
Title: Re: need help with steppers
Post by: jimpinder on February 05, 2009, 12:52:00 PM
If these are eight wire motors, then they have four windings, in the pairs that you know about. The red/yellow are one pair, next is blue /black, (these make up the A and C windings) then white/purple and brown /green (these make up the B and D windings).

The  A and C work together, and the B and D work together.

They can be wired up in series  i.e. red - yellow connected to blue - black -- then the red and black are connected to A and A+
The other pair white - purple connected to brown - green -- then the white and green are connected to B and B+.

5 wire motors have a common, these do not.

In this configuration they are wired in series, and take the least current (but only provide half the power). You can also connect red to blue, and yellow to black for A and A+, and white and brown, purple and green to B and B+. This is parrallel wiring which takes more current, but provides more power.

My motors are Ghekos, wired to 20 Ncm motors, but the Gheckos can provide up to 7 amps. My motors are rated at 2.5amp per winding. In series they take less that 2.5 amps, but in parrallel they take 4. In your case I would wire them in series. If your drives are current limited, it does not matter, but it is better to start small and work up. Try that and see what happens.
Title: Re: need help with steppers
Post by: tubular2000 on February 05, 2009, 10:20:22 PM
you have a unipolar configuration. if you have a dmm, measure the resistance between each single wire and the common group, it should be similar. this will tell you if you have a burnt phase. if it is good then try the 6 different configurations on the motor cable. 1234, 1243, 1423, 1432, 1324, 1342. on each config try to run the motor very slowly like 50 rpm.

an other thing might be that the step and dir input on the board are not labaled properly and you send the pulse on the dir input and dir on the step input, this would cause the motor to heat because it is stalling at full current on a phase.