Customer:
I have several questions about Dambo and stepper motors.
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After connecting Dambo to a Croduino and uploading a program, can Serial monitor be used? Will Serial monitor communicate with the Croduino or with Dambo?
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The examples mention only digital outputs. I assume digital inputs can also be used?
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Some clarification on the frequency detail. By default Dambo is at 1MHz. To switch to 8MHz, I need to call Burn Bootloader. I assume I only need to call it once, and before that I need to complete all those mentioned steps - Processor ATtiny85, Arduino as ISP, etc.? I’m asking so I don’t damage the Croduino bootloader.
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Do I need to remove the battery when connecting to Croduino?
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Not about Dambo but potentially for a project with Dambo. A water valve - the one in your offer is 230 VAC. Can the same one be obtained but 12 VDC?
Also about steppers. Is there a method to check whether my steppers have failed or the A4988 drivers or both? I have two steppers and two drivers that were supposed to be on a robot. Everything turned out quite difficult and the motors couldn’t move it. When I saw it wasn’t moving, I lifted it so the wheels were in the air but they didn’t turn - just heard intermittent sound (like sending pulses) but both motors are stationary. Before mounting the wheels everything worked because I tested it. I suspected the A4988 and fortunately I have another one that wasn’t on the robot and didn’t have that load, but the same thing. Both motors stall on it too and I hear the same sound. I actually acquired that 3rd driver first and both motors worked with it. Unfortunately I don’t have a third stepper to test that combination, so I have no idea how to approach solving this problem.
There might be one more detail. Before I put the robot on the ground I tested if the wheels spin in the air, and everything worked. Now thinking about it, I have the feeling that when the motors would stop, due to wheel inertia, they would spin a bit more. In that case the motor acts as a generator and maybe something happened there. That’s why I suspected the A4988, but then the question is why the motors don’t work with that third one that was always only connected to the Croduino. So I suspect the motors too. I don’t know if they have some electronics in them (probably do) so maybe that failed, though at first glance I’d suspect the drivers.
Is there an indirect measurement method? For example, if I put a voltmeter on one of those 4 pins that go to the stepper and command, say, 2000 steps (10 rotations), shouldn’t I read some voltage? Due to rapid changes it will apparently be smaller but that’s fine, the important thing is to see it. If there’s no voltage at all, is that an indicator the driver isn’t working? And check all 4 pins that way.
Originally submitted via email support on 22 February 2018. Migrated to the forum for community visibility.
Soldered Support:
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No, Serial monitor goes over serial communication, while Dambo is programmed over SPI. If you need serial communication on Dambo, you need to connect TX/RX lines from Dambo and Croduino together, so you can use the CP2102 chip that’s on the Croduino as the chip through which you’ll communicate with the computer. There’s also just a CP2102 breakout for direct connection, but it comes to the same thing: Soldered: Open-Source Electronics, Boards, Sensors & Modules – Soldered Electronics
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Of course 
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That’s right. Once you burn the bootloader on Dambo and it changes permanently. Settings all stay the same, and the programmer should be Arduino as ISP.
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Yes!
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Yes, we’ll get it, it’s already on my list
Have you tried removing the wheels and leaving the steppers in the air to see if they spin without any load?
Which motors do you have? Maybe they’re just not powerful enough.
Can you try adjusting the voltage with the potentiometer on the A4988 board?
With a multimeter you won’t be able to measure anything because the voltage changes are too fast. But I think you should read some voltage…
Customer:
Thanks for the answers, everything’s clear, just a bit more about the steppers.
The steppers are Nema17 and I got everything from you - both the steppers and the drivers. The motors rotated properly before mounting the wheels. While I was programming Nova and determining the direction of rotation, I had a clothespin on them so I could more easily detect the direction. So the combination of motors and drivers worked fine, only the motors might be too weak for installation on the robot.
After testing with the robot, I removed the wheels and they don’t spin - that is, without load. All I hear is a sound like squeaking, as if for example a metal shaft were scraping against another metal. That would make sense if the shaft were rotating, but it’s stationary and I hear the sound, so I assume the cause is some high frequency, say pulses from the driver. At one moment the motor showed a tendency to turn, and it even turned a little, but that wasn’t continuous rotation, and I commanded 2000 steps. I’d suspect the drivers that maybe failed due to excessive load, but I’m confused because I tested the motors with the third driver too, which previously turned those same motors without load - that is, it was never in a situation to be under excessive load that would damage it. And the same thing. Same sound and motors are stationary. By that logic I should suspect the motors because I tested with a driver that should theoretically be fine.
I measured the voltage on the potentiometer and it’s approximately 500mV. I read somewhere that it should be between 350 and 500 mV measuring between GND and the metal tip of the potentiometer. I don’t know if that’s how it works? On the third driver it’s the same voltage, which makes me even more suspect the motors rather than the drivers.
If they’re failed, they’re failed, no problem. I just need to know where I went wrong so I don’t repeat it in the future. Only first I need to determine what failed.
Soldered Support:
Honestly, I don’t really know what could be the issue here. I’ve worked relatively little with steppers so I probably aren’t much smarter than you in that regard
This squeaking sound and what you hear sounds like there isn’t enough current to move it. ALTHOUGH it could also be a physically damaged motor, which from your description seems to be the case…
On the potentiometer pin (the middle one) is Vref, the reference voltage that tells the chip how much current to send to the steppers. If you have small steppers, this shouldn’t be a problem, but if it’s large ones… maybe it’s better to increase that voltage to increase the output current. Don’t worry, with too much current you can’t burn anything because the device will draw as much current as it needs.
If you’d like, I can send you steppers/motors to your address so you can test what exactly failed, and you can send them back to me when you’re done testing