Dolly DRV8825

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3DEnthusiast
Posts: 66
Joined: Fri Oct 27, 2017 6:50 am

Dolly DRV8825

Post by 3DEnthusiast » Mon Nov 06, 2017 9:41 pm

I received some new DRV8825 drivers and plugged them into my Dolly.

Dolly screamed and now it doesn't work. I tracked down the problem to my ATMega board and swapped it with a spare. It still doesn't work. I have a new Ramps1.4 on its way as well.

I saw where it says to turn the DRV8825s down(clockwise) because they come preset kind of hot.

Has anyone else got any other suggestions before I cook another board?

Thanks!

slippyr4
Posts: 224
Joined: Thu Jun 15, 2017 10:24 am

Re: Dolly DRV8825

Post by slippyr4 » Tue Nov 07, 2017 9:07 am

Yep, when setting up a new driver, don’t plug your motors in until you have set the Vrefs. And don’t physically plug/unplug the motors when powered on.
Self-built Prusa i3 MK2 clone
My things: https://www.thingiverse.com/slippyr4/designs
My Prusa firmware port for ramps & MKS : https://github.com/slippyr4/Prusa-Firmware

3DEnthusiast
Posts: 66
Joined: Fri Oct 27, 2017 6:50 am

Re: Dolly DRV8825

Post by 3DEnthusiast » Tue Nov 07, 2017 10:46 pm

Hopefully I didn't cook my motors too, then. When I get the new board in and everything connects, I'll add the motors on layer.

Thanks!

3DEnthusiast
Posts: 66
Joined: Fri Oct 27, 2017 6:50 am

Re: Dolly DRV8825

Post by 3DEnthusiast » Fri Nov 10, 2017 11:48 pm

Okay... I'm at a loss. I replaced the Atmega board, the Ramps 1.4, tuned the DRV8825 voltage without the motors connected and changed the steps per unit in Marlin and the Z axis doesn't move but makes a grinding noise. The Y-axis makes the same grinding noise as well. The extruder is doing it too.

The X-axis moves perfectly.

I replaced the DRV8825 with the A4988 on the Z axis and reset the steps thinking that would help. It did not.

Maybe I didn't cook the motors?

I'm so confused. Are there different versions of Ramps 1.4? this is the board I got.

https://www.amazon.com/gp/product/B01E5K98C6/

chumm
Posts: 176
Joined: Thu Jun 15, 2017 11:24 am

Re: Dolly DRV8825

Post by chumm » Sat Nov 11, 2017 3:16 am

That board should be fine. I'd start with trying the X motor driver and X motor, which you know are working, with the other motors/drivers/slots on the board to isolate the problem. Grinding usually means either insufficient current or a poor physical connection.

3DEnthusiast
Posts: 66
Joined: Fri Oct 27, 2017 6:50 am

Re: Dolly DRV8825

Post by 3DEnthusiast » Sat Nov 11, 2017 4:28 am

For whatever reason, I had not thought of that. That's a good suggestion and I will follow up on that.

As it stands now, I have all of the drivers tuned to approximately .7V to .8V. If I did the math correctly, that should equal 1.4-1.6A which is just under the limit of 1.7A per motor. Have I done that correctly?

What ends up happening is for the extruder and the Y-axis, the spindle and attached gear look like it's shifting back and forth but nor making solid progress one way or the other. The Z-axis just sounds like gears grinding and it doesn't move. I'll try to get video of it later and post a link.

Regardless, thanks for the suggestions and help.

slippyr4
Posts: 224
Joined: Thu Jun 15, 2017 10:24 am

Re: Dolly DRV8825

Post by slippyr4 » Sat Nov 11, 2017 9:20 am

Your sums are correct for 8825s. I would be very very surprised if your problem was lack of current; that’s quite a lot more than my printer. I’d be pretty sure you have wiring issues. A poor connection to one coil on a motor will do exactly that.

Power down and test the motors with a multimeter set to lowest ohms setting. Stick the probes down in the top of the motor connectors on the board, squeezing in next to the wires. You should get a similar but low reading from each pair. If you don’t that might indicate where your problem is.
Self-built Prusa i3 MK2 clone
My things: https://www.thingiverse.com/slippyr4/designs
My Prusa firmware port for ramps & MKS : https://github.com/slippyr4/Prusa-Firmware

3DEnthusiast
Posts: 66
Joined: Fri Oct 27, 2017 6:50 am

Re: Dolly DRV8825

Post by 3DEnthusiast » Sat Nov 11, 2017 10:30 am

I replaced the Z(2), the Y and Extruder motors, thinking I had burnt the old ones out. So these are all new motors doing the exact same thing that the "bad" motors were doing. Maybe I didn't burn those motors out after all.

It's confusing how these things worked with the A4988 and then when I shifted up to the DRV8825s, it doesn't. Granted, I used an all new Ramp1.4 and Arduino Mega 2560 Uno R3.

This thing worked for a brief, glorious moment in history.

3DEnthusiast
Posts: 66
Joined: Fri Oct 27, 2017 6:50 am

Re: Dolly DRV8825

Post by 3DEnthusiast » Sat Nov 11, 2017 2:51 pm

Update.

I swapped the X and Y motors on the board. The Y motor (brand new) did the same thing it's been doing when I moved X in pronterface. As expected, the X motor (original) worked just fine when I moved the Y.

I'm hard pressed to think that it's the wiring that's wrong since it's the exact same wires I used when the machine worked in the exact same config.

I'm truly baffled by this. Is there a setting in Marlin that maybe I needed to adjust? My steps per unit I doubled from 100, 100, 400 to 200, 200, 800.

This makes no sense and I'm sure it's going to be something simple.

Maybe a missing jumper somewhere?

slippyr4
Posts: 224
Joined: Thu Jun 15, 2017 10:24 am

Re: Dolly DRV8825

Post by slippyr4 » Sat Nov 11, 2017 6:17 pm

Motors can be wired quite differently even if the colours are the same. Have you verified which wires the coils are on with a meter?
Self-built Prusa i3 MK2 clone
My things: https://www.thingiverse.com/slippyr4/designs
My Prusa firmware port for ramps & MKS : https://github.com/slippyr4/Prusa-Firmware

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