Hello, I am trying to drive 3 stepper motors from a DC power supply. I have 2 nema17s and a nema23. The 17s are rated for 1.7 amps and the 23 is rated for 2.8 amps. I have the 3 motor drivers in parallel with the power supply. When I run a code to turn the motors in a sequence they do not have enough torque to even spin without skipping. The power supply is rated for 30V 10amps. The motor controllers need 9V for operation. When the power supply is at 10V, the current is 2.2A. But when I increase the voltage, the current decreases.
Does anyone know why it would be trying to keep the same power? ~23W
That's weird, but stepper-motor current is a little "weird" (the current might be independent of the load or more-independent than a regular DC motor) and you're measuring a pulse so a meter won't be accurate (but it should show an increase or decrease correctly).
So that's a variable power supply? And the motors are 10V rated?
And the motor drivers have sufficient current rating? There will also be a little voltage drop (loss) across the drivers.
Maybe that's the problem. Maybe they don't have enough torque for the load. It could also be speed related. Steppers can't start-out at full-speed so depending on how fast you're running them (and the torque load) you might have to ramp-up the speed.
It is a variable power supply up to 30V or 10A. I can limit the current if the system is trying to draw more current than what I have the dial set to.
I set the supply at 10V because the drivers require at least 9V. I have increased the voltage all the way to the limit of 30V but then the current decreases.
I don’t have any load on the motors and they are skipping. I simply have a small aluminum pulley for a timing belt.
I have the current limits set to the rated currents on the drivers. I have the limit set on the nema23 to 0.1A lower than the rated current. I’ve also tried increasing the limit and it didn’t make a change.
The drivers are also set to 200 steps per revolution which is what the motors are. So I’m not microstepping
If the current limit is set to the motor rated maximum, and ramping up the speed doesn't work, then the steppers can't provide the required torque.
For successful system design, the torque requirement must be known, and steppers should be chosen with a generous torque margin -- often a factor of two.
Are you setting the current limit on the power supply or by changing resistors on the stepper controllers? Sounds like you are setting the limit on the power supply.
No, that's not weird. Its the normal behavior with a current driver for a stepper.
The voltage of the power source should be as high as possible - of course within the limits of the driver. The current of the motor must be set at the driver, not the PSU.
I have the current limits on the motor drivers to the rated current of the motors. The motor drivers have switches that are set in a configuration that will limit the current based on those switches kind of like binary. Like off off on will set it to a certain limit and off on off will be another limit. The driver has a table that shows what configuration is required for a certain limit.
The power supply can limit current or voltage based on what the system is drawing. If I set the current limit below what the system is drawing, it will maintain the limit I set. If I have the current limit set above what the system is drawing then it will maintain constant voltage and supply the current that the system needs.
I have the current limit set to the supply’s max which is 10A and it is never drawing more than 2.2A even though the motors should be drawing much more than that.
Because that´s the power your steppers need. That is controlled by your driver. Where should additional power go?
What drivers are you using, and how are they wired?