Stepper Motor Velocity

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nlund

Stepper Motor Velocity

Postby nlund » Mon Oct 03, 2011 10:33 am

can anyone tell me how to change the velocity setting (or dwell time between pulses) to reduce the stepper motor speed below the value of VelocityMin?

Thanks!

erik
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Re: Stepper Motor Velocity

Postby erik » Mon Oct 03, 2011 10:49 am

In actuality, the Velocity settings are changing the speed, so only the magnitude of the velocity is changed, not the direction.

To get a negative velocity, you must set the target position to a value below the current position and then the Velocity limit that you set will apply for both positive and negative velocities.

If you are looking to have different forward and reverse velocity limits, then you will need to add some logic that will change the velocity limits on the fly.

nlund

Re: Stepper Motor Velocity

Postby nlund » Mon Oct 17, 2011 8:11 am

Hi Erik,
Thanks for the input.
Having re-read my first note, it may have been a little confusing, allow me to rephrase it.

I'm hoping to adjust the velocity of the motor (rotational speed) to fractional values between 0 and 1. Where 0 is a stopped motor, and 1 being the slowest speed obtainable with the phidgets stepper control panel.

I think I'm looking for the programming variable that controlls the dwell time between motor step pulses. I tried adjusting the C# variable attachedStepper.steppers[0].VelocityLimit to fractional values but it appears to be defined as an integer and won't reduce the motor speed below the value of 1.

I'm not sure if I'm trying to use the right variable, or if there's a better way to go about this.

Thanks!
Niles

erik
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Re: Stepper Motor Velocity

Postby erik » Mon Oct 17, 2011 9:29 am

The velocity is measure in microsteps per second. For the 1063 with the Velocity set to 1, that would be 1/16th of a step per second, and for the 1062 that would be 1/2 of a step per second. Are you looking for an even slower speed?

The only way to get slower speeds would be to attach a gearbox to the stepper, reflash the firmware with even more complex code, or to set the velocity to 1 for one second, then 0 for the next second and repeat to essentially get a velocity of 0.5 per second, but with jerkiness.

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Patrick
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Re: Stepper Motor Velocity

Postby Patrick » Mon Oct 17, 2011 9:45 am

Or to set the position one step at a time, at exactly the speed you want.

-Patrick

nlund

Re: Stepper Motor Velocity

Postby nlund » Mon Oct 17, 2011 10:40 am

The position to position option is probably the route I'll try next.
Thanks for the suggestions!
Niles


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