Hi,
I want to use a DRV8825 to control a stepper motor, and I don't know where I have to put my multimeter to mesure Vref to set the limit current.
This is the datasheet of the DRV8825: http://www.ti.com/lit/ds/symlink/drv8825.pdf
Pololu - DRV8825 Stepper Motor Driver Carrier, High Current (md20a).
Also do I have to connect the GND of Arduino to the GND of motor supply?
Thanks in advance
Yes, grounds must be commoned - including for the Vref measurement - meter between Vref and ground.
thanks for your answer, but where is Vref on the board?
On the wiper of the preset pot on the board.
I am sorry Mark, but I'm not really fluent in english.
I don't know what is a wiper?
Could you please show me by adding an arrow on the attached schema where is it?
Also, when can I do this measure, I mean the DRV8825 should be powered On but the motor supply shouldn't be connected, is that right?
Many thanks again for your time!
With a potentiometer there is a resistance track connected at each end to a terminal.
A third terminal connects to a movable contact that wipes over the track, hence the wiper.
The Pololu DRV8825 web page has very good instructions.
...R
Hi,
to start with the DRV8825, I take an old stepper motor from a printer.
I have no information for this motor, so I power the motor with a 9V battery and I start with vref at its lowest value, nothing happened, then i turned the potentiometer a little and the motor start turning perfectly.
then I decided to replace the 9V battery by a 12V power supply, but nothing happened and I don't know I check all the wires and they are OK
You need to measure the motor winding resistance to estimate the current needed. All motors of
similar size have roughly the same power dissipation (this is a thermal dissipation limit really),
so you can use this estimate of power plus the winding resistance to estimate the current since
P = I^2 R
Set your DRV8825 board to the relevant Vref for that current.
Any other issues will be wiring, power supply which you troubleshoot with a multimeter.
@ELECTO, have you looked at the Pololu DRV8825 web page as I suggested in Reply #6?
It is much easier to help you if you respond to each of the Replies.
What sort of 9v battery were you trying? The little PP3 type of battery is useless for driving a motor.
How many amps can your 12v power supply provide?
What is the resistance (ohms) of the stepper motor coils when you measure it with your multimeter?
...R
sorry If I don't answer quit well.
In fact, I obtained the 12 volt by division with 2 same resistor on a 24V/5A power supply.
I decided to remove the 2 resistors and supply directly with 24V and everything worked well!
So I decided to use the original stepper motor that I want to use from the begining which is 1A/phase and 14ohm/phase.
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?
You probably just measured the impedance of the decoupling capacitors that way. Check Vref without
the motor attached and power down, reconnect motor and then try.
I totally disconnect the DRV8825, and I find continuity between Pin Vmot and Pin GND.
I don't why because the driver was not hot at all!
ELECTO:
sorry If I don't answer quit well.
There does not seem to be any value in apologizing and then continuing to not answer the questions.
In fact, I obtained the 12 volt by division with 2 same resistor on a 24V/5A power supply.
You cannot reduce the voltage for a power supply with two resistors acting as a voltage divider.
...R
I check the decoupling capacitors C1 (4.7µF), C2(0.1µF) and C3(0.1µF) on the DRV8825 board and it seems that they are shorted (continuity between the 2 extremity), do you have any idea about how is it possible?
