Hello
I have bought a DRV8825 Stepper Motor Carrier boards for running a pump with a stepper motor.
The issue I have is this: I can get it running ok, but the current needed is about 1.5 A. This should not be a problem. I have checked the reference resistance of the driver to set the current. I set it at about 1.6 A current.
It ran for a few seconds and then stopped.
The Arduino nano I am using was not lighting up as before. I tried loading the sketch on the nano again and the nano had died. I cannot see why that would be. Any thoughts on why too much current draw on the 8825 would damage the nano?
Thanks.
Big Kiwi
Hi @BigKiwi,
Hmm, interesting situation to be in. Reading in-between the lines, the nano, motors and everything else was working OK before you dialed up the current on the DRV8825. So the only real variables here are the power supply and back EMF.
The main way people come undone with their Nano is having both Vin connected and USB power. The two supplies fight, the Nano usually looses.
Besides the above, these thoughts come to mind in no apparent order:
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Check the flyback diodes are serviceable.
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Test the DRV8825 in isolation without an MCU. Once confident, grab another MCU of any flavor to retest.
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Vin is rated to 12V, recheck the power supply isn’t going higher.
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Remove the 12V supply, test with the Arduino on it’s own, disconnected from other things and only connected via USB (to see if it’s an onboard Vreg issue)
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If you observed any heat, whatsoever on the Nano then perhaps there was a wiring issue. It’s hard to go back in time though if you didn’t get a chance to observe that.
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Try control the DRV8825 with another MCU or manually
Hi Graham
Thanks for the comments and analysis.
Electronics is not my main area of knowledge so I am going to need to ask some questions to get further understanding. Appreciate your help with this.
Firstly, this unit was only run on battery, so no USB power comes into the equation.
The other points you raise are where I would like some more info.
Flyback diodes. Are these ones on the nano or DRV boards or the one that is in my schematic by the MOSFET? If on the boards can you please assist with their ID and position so I can test them?
How would I test the DRV8825 without an MCU? With my limited understanding the MCU is what runs the DRV8825.
Vin is 12V from a battery, so it may actually be as high as 13.5V at times.
The Arduino does not appear to respond or be recognised by the IDE once it has been hit by this issue. When the nano is plugged in and I check Tools/Port there is no port used by the nano. I would be interested to know how I can test or fix this as over the last month I have accumulated 4 nanos that are suffering from this as I have tried to fix/find the problem. If I can recover them that would be great.
The only heat I observed one time was in the wire to the VMOT pin of the DRV8825. This was due to the board initially being wound up to running 3 A, and the jumper lead couldn’t handle that and burned up the insulation.
I hope that provides some more clarity on where I am at, and I would certainly appreciate help on any of the points above on the diagnosis.
Regards
Hi @BigKiwi,
If you are using a genuine Arduino Nano, then the onboard LM1117 regulator should be able to handle 13.5V despite the rated 12V max on the Arduino.cc website.
Flyback / Back EMF diodes are those positioned from V to GND, in reverse polarity. The do all the heavy lifting with protecting your circuit from back EMF which is generated when motors accelerate / brake, and safeguard against inductive loads in general. There are at least two of them on the “Mixer Motor” and the “Air Pump”.
Oh. That’s horrible! Something is not right with your setup then. This certainly isn’t normal and you should be able to get years of use from a Nano. I’d be starting from scratch if in your situation. Connect an ammeter in series with the battery and monitor the current load of the circuit, notably the current being drawn by the Nano.
From there, connect a back EMF diode right next to the Vin pin along with a 0.1uF+10uF capacitor. This creates good protection from spikes, dips and inductive loads.
With the safety circuit in place on Vin, and the ammeter in use, I’d go step-by-step and monitor what’s going on with each major change.
No easy answer for you. Something is certainly wrong though.
Hi Graham
Thanks for the further comments.
I was not sure if you meant the diodes in my circuit or that there were diodes on the Nanos.
Answering your question. I have managed to damage one Arduino Nano, and 3 knock off nanos, and yes killing them is horrible. 
Re the diode and capacitors, this is where my general knowledge starts to get hazy.
Are you saying that I should put a flyback diode across the 12V to GND of the line that powers the nano?
And similarly put the two capacitors you suggested across the 12V to GND as well. These caps go in parallel not series I assume? Can you please explain why I would use the 0.1 and 10 uF caps. My knowledge does not extend to understanding how or why one is not enough. That would be appreciated to help me improve my knowledge.
Anyway, once I have confirmation from you that this is what I need to do, then I can put that in place and try it out.
Thanks again.
