But I decided to start with an old bipolar stepper motor find on a old printer, the only information that I find is the winding resistance (17 ohms). I supply my project with a 24V/5 A power supply.
Before powering the system, I checked Vref (I followed the procedure on your youtube video) and I obtained Vref=0,003V (almost the beginning positio of the Pot). after powering nothing happened!
I decided to turn a little the pot and I find Vref=0,125V and after powering the motor turned correctly!
I turned again the pot, I find Vref=0.34v, after powering the motor didn’t turn and was noisy!
so I get back to the second position and the motor turned again!!
So I decided to use the original stepper motor that I want to use from the begining which is 1A/phase and 14ohm/phase. (It is an unipolar motor with 6.7ohm/phase and as I use it as bipolar one (without common wire) the winding resistance is almost 14 Ohm/phase, I hope I’m right).
I leave the pot at the position where Vref=0,125V and when I powered, the motor turned perfectly!!!
I decided to turn the pot a very little and after powering nothing happened.
now when I power the DRV8825, the green LED of my power supply directly turn OFF, after some check I find continuity between Vmot and GND!!
Is my driver KO?if yes, I thought that there was a current protection? (also the driver was not hot!)
Thanks in advance for your help and sorry for my english!
I measured Vref and i obtained 0.125V which correspond to 0.250A, I said ok I can connect the motor there no risk, so connected if and the motor turned perfectly!!!
I don’t know why I decided to turn a very, very little the Pot on the DRV8825, I powered and nothing happened, I get back to the initial position and nothing again, I decided to check continuity with multimeter, and I find continuity between Vmot and GND!!!
Is my DRV KO?
I use a DRV8825 to control a unipolar stepper motor 1A/phase 6,7 Ohm/phase: docs-europe.electrocomponents.co … 32eb0c.pdf
I connect it as you advice on your website (by not connecting the 2 common wires).
I measured Vref and i obtained 0.125V which correspond to 0.250A, I said ok I can connect the motor there no risk, so connected if and the motor turned perfectly!!!
I don’t know why I decided to turn a very, very little the Pot on the DRV8825, I powered and nothing happened, I get back to the initial position and nothing again, I decided to check continuity with multimeter, and I find continuity between Vmot and GND!!! it that normal?
If there is no resistance between the VMOT and GND pins, it is likely that there is a short in your system somewhere. If you have the driver carrier board in a socket or on a breadboard, you might try removing it from the rest of the circuitry and testing it with your multimeter again to see if the short is on the board or somewhere else.
These drivers do limit the current passing through and have thermal protection as well, but there are many ways electronics can be damaged. Did you have an electrolytic capacitor installed in your circuit close to the driver board? If you post pictures of your board and all of the connections to it, I can look for anything that might be out of place.
Perhaps I didn’t understand what you mean when you said :“If there is no resistance” because when I said there is a continuity I mean that there is a small resistance (I measured around 1,3 ohms between Vmot and GND with the driver totally removed from the rest of the circuitry).
I checked on a new driver and there no resistance between Vmot and GND and it works well.
Concerning the electrolytic capacitor, I took an old one 470µF 16V (I’ve just realised that it is not appropriate because I use 24V power supply). With the new driver I decided to use a 100µF 50V electrolytic capacitor.
It seems like the 16V capacitor probably failed when supplied with 24V. Failures like that are not always immediate. Once the electrolytic capacitor failed, your board was vulnerable to LC voltage spikes. The low resistance between VMOT and GND is consistent with the type of damage an LC voltage spike can cause. If you contact us via our support email and mention this forum post, we might be able to help you out with a discount towards a replacement.
