im new here (from germany) and need help to get my driver work.
At the moment im using die drv8825 in combination with the:
Stepper Motor: Bipolar, 200 Steps/Rev, 28×45mm, 4.5V, 0.67 A/Phase
and
Raspberry Pi Model B v2.0.
My Problem is that when i am trying to run the motor it jerks one step forward and then directly one step backward.
I am giving the step signal from my raspberry pi with an Outputvoltage of 3 Volt and an frequency of 10 Hz.
The Vmot supply is 15 Voltage und the current ist limited by 1 A.
The Logic Supply from my raspberry is 5 V and the step-Signal has a range of 3 V.
Im also using the “Minimal wiring diagram for connecting a microcontroller to a DRV8824/DRV8825 stepper motor driver carrier (full-step mode)” like in the next picture:
I tested also every combination and the support in germany is very bad. So i hope i get here an better support.
It sounds to me like one coil is not connected properly or is not working (open). Can you check the resistance of both windings with a multimeter? You should read about 7 ohms each. If both are OK, check the solder connections to the driver board. Finally, check the voltages across each coil, at the board terminals for several steps (slowing down the stepping action as much as possible).
Incidentally, the 0.67 amps/phase rating is maximum. If you drive more than that through each coil, the motor will overheat.
The motor is connected by this diagramm:
Black - A1
Grenn - A2
Red - B1
Blue - B2
I also found a topic in this forum which describes my Problem in almost 100%. But the topic was not completed successfully. Her the topic link:
I also have the problem that my external power Suply always is going to its current limit, the motor sums and with every step it jerks one forward und jerks one back. Yes, and the motor gets a little hot but i dont let this run likt this more then a minute.
I also have checked the output signal to the motor but forgot to look after the Voltage aomplitude (Sorry). But i recognized that there is somthing wrong but i cant incidacte the problem.
Tomorrow i will check the output Voltage und make a picture of the oscilloscope.
FYI: i have two of these driver. both with the same “problem”.
You MUST set the current limit properly on the DRV8825, following the instructions on the product page. I had assumed that you had already done this, but now it sounds like the power supply is limiting instead. This will not work!
But its not loigcal for me…because if Potentiometer on my board is to set the current limit, then it should not matter if i set the current limit at my power supply or at the driver when i turn on the potentiometer to 100%.
So…its an current regulator, which controls the current proportional to “Vref”.
The two current limiting operations are quite different and as you have seen, one works and one doesn’t. The power supply is probably a “constant current” limiter, which means that if the load starts drawing more current than allowed, the voltage to the load is reduced accordingly.
In the motor driver, the voltage to the motor is switched off the instant the current limit is reached and then turned on again some time later, so that the average power to the motor coils is reduced.
