I need to run a motor at pretty high speed (20rps = 1200rpm) but the torque required is very small.
At the moment I use the motor https://www.pololu.com/product/2299 together with driver https://www.pololu.com/product/2128.
It operates smooth till 2000 full steps per second (10rps) but after that it stalls. I tried different acceleration curves and full and 1/16 steps but the result is almost the same.
Which pancake motor you would recommend in order to have a stable performance at ~1200…1500rpm?
Hello.
We do not have a specific recommendation. The pulse rate-torque graphs (sometimes called pull out torque curves) in stepper motors’ data sheets are a good place to look for information about how well the stepper motor can handle high step rates, though other aspects of the system can have a large effect on the maximum step rate. You can read about results from varying the power supply voltage and using a flywheel with a different stepper motor in this post on our forum.
The datasheet for the SS2502 motor you have makes it seem like you might be able to get the motor running faster than ~600rpm (about 4 kpulses/s in the half-step pulses the graph in the datasheet uses). What supply voltage are you using right now?
-Nathan
I tried up to 24V, but at 1000-1100rpm it is not really stable even with smaller than 1/2 step. It might spins for 30s and than suddenly stall. 
Do you have any kind of flywheel on your motor shaft? That can help achieve faster stepping speeds. What do you have VREF on your driver set to?
The DRV8825 motor driver has a higher absolute maximum voltage than the A4988 (45V instead of 35V), so you might be able to use one with a 36V power supply to get faster speeds. Also, our 42mm Sanyo pancake stepper motors seem to have a little higher stepping speed than the 50mm one you are using right now, though it is not clear to me you would be able to get the speed you need out of them. You might look at the pull-out torque curves in the datasheet for them to try to judge for yourself whether they might work (on that datasheet, 5,000kpulse/s is 1500rpm).
- Yes, I use VREF. The current limit now is 0.75A (according to the formula from the datasheet)
- At the moment the motor is attached to the gearbox (28:1), but I tried to run it without any load and just with shaft collar. The result is almost the same.
- 36V power supply might give me an answer, but It doesn’t work for my final design: we have only 24V available, so, 36V requires step-up conversion which doesn’t make me happy.
Which step size would you recommend in order to obtain best performance?
PS: I’ve purchased the smallest 42mm Sanyo pancake and expect to have it soon.
We have not really characterized how microstepping would affect the maximum motor speed, but my general sense is that the step size probably doesn’t matter much, and to the extent it does matter, I suspect using full-step mode could be slightly better than microstepping. I will try to test it out soon.
-Nathan