Dolly DRV8825

#1

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!

#2

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.

#3

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!

#4

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.

#5

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.

#6

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.

#7

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.

#8

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.

#9

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?

#10

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?

#11

Alright, on a whim I put the old motors back in and they all work again. No problems at all. This has been crazy.

My only problem now is the extruder does not seem like it’s working with either motor, new or old.

Edit: nevermind. The extruder works.

#12

How hot should the motors be getting? How hot is acceptable? My X and Y seem pretty hot. I can hold the X axis motor in my fingers for a long time but it seems just below too hot to hold.

#13

Too hot to hold is a convenient guideline for whether the motors are too hot for continued operation. 60-70 C is roughly the recommended maximum temperature for most standard steppers, anything over 80 gets into damaging territory over time. Since you can heat your bed and test your hold temp (all our hands are differently calloused, after all,) try heating your bed to 60ish and comparing the feeling with the motor.

You should be able to dial things down a bit too on the X and Y motors. I find that usually only the extruder motor, when there’s no gearing-down, needs enough current/torque to get significantly hot during operation. Your motors will run hot if the vref on the driver is turned up regardless of whether they actually need that much current, so it’s easy run them unnecessarily hot.

#14

That’s good to know. My X and Y are not as hot as the Heated bed when it gets to 60C. Still, I might try to tune them down a little.

Thanks!