Z-Axis Motor Not Moving and Unreliable

For assuming direct control, it’s easiest to install the Arduino IDE. Open the IDE and plug in the cable between computer and arduino. Go to Tools - Port and set the port used. Go to Tools - Serial Monitor. Set Baud to 115200 and line ending to Both NL & CR.

Now you can type in the top line of the screen. G00 X100 Y200 Z300 will move to 100,200,300. F11 will home x axis, F12 the y axis, F13 the z axis.

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I’m going to try and test this out today.

I will definitely ask you what lines ill need to remove/add to make these changes later.

For the next few hours I’ll just increase the step count so I can prepare to show the farmbot off today to some of the school districts.

I’ve completed assembly and testing the controls. I’m playing with the axis and checking if motor settings are okay.

Testing the Z-Axis was a bit tricky at first. It only accepts negative positions, so using the web app I enabled positive positions. I have “bottomed out” the axis, then pressed “Zero” on the Z-Axis, and turned “negative only” back on.

I figured, that way I can always “bottom out” again by going to “zero”.

Then I told the bot to go to -400 on Z-Axis. While it’s moving, the web app updates the text box with its current position in transit. At -267 the arduino reported “stopped” but the Z-Axis kept moving to -400.

I heard some clicks, and now my farmbot thinks the Z-Axis is at 0 but actually it’s at the top. And since it won’t accept positive positions anymore, I can’t move it back down unless I re-do all the steps I wrote above.

This happened twice now doing the same things. It seems the arduino stops and starts during “long” travels.

As a note, I’ve noticed that sometimes I just hear some clicks of the motors, and the Z-Axis beeping noise (from being constantly powered) goes away, then about 10 seconds later it’s back.

I think the system power cycles or something. I have some horrid wifi coverage in my attic, where I’ve built the FarmBot.

Could it be that the bot reboots when it loses internet connectivity?

If so, is there a way to prevent the farmbot from re-zeroing all axes? This will be a problem in the future otherwise.


this has been a current issue I know some of us Farmbot users have been experiencing.

Sometimes the farmbot does get confused and thinks it’s at the 0,0,0 position after a failed move.

but it’s more than likely possible that the location of your FB is affecting the WiFi connections stability.

As a first step,t you could try to hook up an ethernet line to the FB and see if that helps the movement issues - If it fixed the issue then at least you know its the WiFi connection.

Here is a video of Z-Axis misbehaving. I can reproduce this issue reliably every time by doing these steps:

  • Power off, position all axes as seen in start of video.
  • Power on, bot is at 0,0,0
  • Move absolute to -800, 800, 400
  • Bot moves as seen in video
  • Go back to 0,0,0 (NOT homing, because that makes each axis go individually)

The Z-Axis starts to spaz out when X and Y finish their travel. It looks like Z is missing a lot of steps, causing the Axis to slowly drop down again. When Z starts to decelerate, it picks up again and goes up slightly.

  • Bot now thinks it’s at 0,0,0 but it’s more likely to 0,0,250.

Video: https://drive.google.com/file/d/0B8PVEtF0Y5mNQ2F3QUNxVC1JY0k/view?usp=sharing

So it’s the Z axis that’s making that sound at 0:33 within your video?

for some consistency, I always center it manually and then hit the “Zero X, Y and Z” buttons and a means of electronically letting the farmbot know its @ 0,0,0 now, instead of starting up the farmbot and letting the farmbot determine that its starting position is 0,0,0.

this may actually not have much of an effect but I feel like the farmbot respond’s better if you give it a home x,y,z input from the hardware settings page.

as a whole, whenever you are executing sequences make sure the farmbot Z axis has “negative coordinates only” toggled on.

whenever you are giving it a move absolute through the “controls” tab you may need to toggle the switch for specific input movements to get the proper response out of the farmbot.

good on ya with the video - that really helped get an understanding of what exactly is happening.

just in case let me see get @Gabriel - He has the hardware knowledge and know-how to possible better provide a solution to your problem.


That depends how your wired the power cable. I have yellow on top, so that I can use positive coordinates to go down. Matter of preference I suppose, and it might have exposed an edge case.[quote=“Cjaramillogrows, post:40, topic:1760”]
whenever you are giving it a move absolute through the “controls” tab you may need to toggle the switch for specific input movements to get the proper response out of the farmbot.

I’m aware of this. That’s why my X is going negative at the moment, it’s just how I’ve set it up in this room now.

Ahh I understand. :wink:
Ok got it, that makes sense.

After the farmbot is done making that sound does it say that it’s in the 0,0,0 position?

or does it say that the movement was not complete?

I’m not using encoders when doing this action. It happily reports 0,0,0.

That’s good to know! and just to make sure, its the Z axis that’s making that noise, not the Y axis trying to push farther than the track allows?

It sounds like it’s not spazzing out but just not getting enough juice to keep going up.

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It’s not Y.

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Then it’s the Z stepper driver that needs some tuning with the screw.

The bot sends it’s 10000 something pulses for 400 mm up so the bot should theoretically go all the way up. Without encoders it doesn’t know of that worked or not, so it most assume it arrives at 0,0,0. If in the meantime the motor doesn’t get enough current to stay in position you get this situation.

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This page could benefit greatly from a follow-up step where you tune the potentiometers so that newbies like me don’t run into these problems. When I get back to work on my bot I’ll try to increase the voltage a bit for the motors and see if this still reproduces.

I wonder if you could reproduce this problem as well. My drivers are all measuring at 600 mV. If you follow the steps above, do you get the same?

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Could you elaborate on the tuning screw stuff? I’d like to give that a shot but don’t really know what to do.

Then it’s the Z stepper driver that needs some tuning with the screw.

For testing, I just turn the screw once clockwise if the motor can’t move like it should, when the motor is not activated. Repeat until motor runs smooth enough. That’s not the correct way, so I’ll give you the official stuff below:

Motor specifications:

LDO-42STH47-1684BC (official motor).pdf (143.2 KB)

The exact procedure from the manufacturer:

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Would this help my X axis movement to not sound so loud and “grindy”?

maybe my X axis motors both need a little more juice.

Anyone attempting this really should measure the voltage on the tuning screw before activating their motors. As such, don’t tune it on a live Z axis (unless you turned off its “always on” function)

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I think tweaking your top speed might help a lot. Could be that you’re hitting a resonance frequency and if you slightly increase or decrease steps per second your motors won’t vibrate at parametric resonance

Ordinarily, when running, your ponytail would move up and down opposite your body motion, and side to side a little bit. But, if the frequency of your run is twice the swing frequency of your ponytail, the ponytail swings wildly from side to side. The two frequencies resonate, and the running motion magnifies the motion of the “unstable” ponytail. That’s parametric resonance.

You can really notice this when your motors are accelerating and decelerating. They will pass a few of these frequencies as they wind up. So make sure your top speed is not dead on one of these frequencies. They way your motor is mounted can alter its resonance frequencies. Re-tighten some screws or worst case, add some rubbers.