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Need help finding drivers to match to my steppers

Posted by chrisg9 
Need help finding drivers to match to my steppers
April 12, 2018 10:37PM
Hello,

So i am retrofitting a statasys FDM 2000.
I have it running stock but it is limited by the software and due to the complexity of the setup i am unable to use any of the existing drivers.

So inside the machine there are 3 PK268-01A stepper motors.
The machine has them wired as bipolar already so that saves me a bit of headache and has them paired off for each coil.
My problem is the motors 2 following variables.
Inductance: 56mh
resistance: 17.2Ohms
according to the gecko drive site to find the max voltage is 32 * √mh = VMAX
So my motor would max voltage is 239 but i know the original system drove it around 40V.


I tried using my DRV8825 drivers but no matter what i do the motor just vibrates back and forth.

What i have tried so far
Adjusting the motor current from low to high
try all combinations of microstepping to none at all
Adjusting the pulse width in the FW 0-5
Driving the chip with 30V 5A psu
Slowing down the steps per mm
Switching the order of the pairs of wires
Motor with load and without.

I know the driver works because when i hook up a much smaller nema 17 motor everything works.
When i move this motor to one of my larger TB6560 based drivers on 24V it works.

My current thought is to use a trinamic based driver
TMC262-BOB40

But i dont want to sink money into dead ends so to speak.

I would like to try to avoid switching out my motors in this machine if possible.

Any thoughts on why the DRV8825 failed to turn the motor and if the trinamic driver would work.
Re: Need help finding drivers to match to my steppers
April 13, 2018 02:23AM
The SPI feature is relatively new to RepRap world. There are Duet controllers with onboard TMC2660 drivers or Marlin based boards with Pololu-style TMC2130 drivers. These might be able to control your TMC262 driver too.
I'd put my money on the latest 1/128 microstepping drivers ( LV8729 ) They are powerful and easy to control.

Edited 1 time(s). Last edit at 04/13/2018 02:24AM by o_lampe.
Re: Need help finding drivers to match to my steppers
April 13, 2018 09:27AM
The TMC262 drivers have the same SPI interface as the TMC2660 used on the Duet, so a Duet should be able to control them with just one small firmware modification. However, I think you may find that drivers based on the TMC262 are designed for much higher motor currents than those motors need.

In your position I would probably buy a bare RAMPS pcb, populate it with 50V 100uF capacitors instead of the usual 16V, and try various plug in drivers with a supply voltage up to a little less than the rated voltage of the driver.

I am surprised the DRV8825 drivers didnt work at all. Possibly the current was set too high or the pulse width too low.

To get a decent speed from those high inductance motors, you will need to use a high driver supply voltage.


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Large delta printer, and other 3D printer blog postings: [miscsolutions.wordpress.com]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet [www.duet3d.com].
Re: Need help finding drivers to match to my steppers
April 13, 2018 10:24AM
I dont have a picture right now but i did take the voltage and ground drive pins and moved them to the top side of the board so i could bypass the ramps board.
So i connected my 30v 5a psu and tested and they still vibrate with the larger motor, again when i switched to the smaller motor it worked granted the nema 17 was not happy with 30v and sounded bad.

How would i calculate the needed pulse width for my steppers?
Re: Need help finding drivers to match to my steppers
April 13, 2018 04:39PM
Well i think i came across the reason my DRV8825 drivers were not working with the larger motor but worked on my cnc controller
The 1a,2a 1b,2b are different on the controllers.
on my cnc machine it is 1a, 2a is a pair and 1b, 2b is another pair.
But on ramps its 1a 1b and 2a 2b.

I never connected it this way thinking i would fry the drivers.
Going to test and update tonight.
Re: Need help finding drivers to match to my steppers
April 14, 2018 03:42AM
I don't think, switching stepper wires will work.
I've noticed these weird labels on various controllers, but I never had to change the stepper wire order. It is always black,green / blue,red.
Your steppers were already humming, which means the coils were energized.
By wiring them black, blue, green, red, they will not be energized.
Re: Need help finding drivers to match to my steppers
April 14, 2018 07:33AM
Different motor makers use different colors of wire. There's no standard. And some motors has a connector and there isn't any colored wire. You have to have a data sheet on the motor to sort out which wires are which or use a meter to check resistance, and then experiment with swapping the wire in one phase if the motor doesn't run the first time you plug it in.

Be sure to kill power to the driver when you connect and disconnect the cable. If you do it while the driver is live you're liable to destroy it.

Edited 1 time(s). Last edit at 04/14/2018 07:33AM by the_digital_dentist.


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Re: Need help finding drivers to match to my steppers
April 14, 2018 05:13PM
Well good news i was an idiot.
It was my wires after all. i switched them and now they work.

Now sometime next week my new trinamic drivers will be in and they should have no problem driving these motors going to try to give them 38V
Will update once i make more progress.
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