Selecting discrete motor speeds with Tic T834

Dear Pololu forum,
Apologies if this information is already in the documentation or the forum, I wasn’t able to figure it out. I am hoping to use the Tic T834 to control a low voltage stepper motor (rated voltage 3V). My application is an improvement of my star tracking camera mount ( Ideally, I would like to have a switch with multiple positions, to select the stepper motor speed as one of 3 or 4 values (corresponding to the speed required to track the stars, the Sun, the Moon). Is this possible, and if so, what would be the simplest way? I am trying to avoid an external controller (eg arduino, computer), and I don’t think the analog input with a potentiometer is exactly what I want, since I don’t want to allow a continuous set of speeds, only a discrete set (3 or 4 specific different speeds).
Apologies again if this is a trivial question, and thank you for any help!

Hello, Emmanuel.

That sounds like a really neat project!

The simplest way to do something like that without using a separate controller would probably be to set up a 4 position switch with some additional circuitry (e.g. resistors to make various voltage dividers) so it gives the Tic a different desired analog reading at each position. I do not have any specific suggestions for a mutti-position switches, but you can probably find some on a site like Mouser or Amazon.


Hi Brandon,
Thank you very much for your help and encouragements!
Using several voltage dividers as opposed to a potentiometer does sound like a good way to input well-defined analog voltages into the Tic.
I am just realizing that the motor speeds needed for the various tracking modes are very close to each other (they differ by less than a percent for sidereal and solar tracking for example). So this may make it hard to use voltage dividers with the linear response mode, as my resistance values in the voltage dividers would have to be very accurate.
Just in case, if a new version of the Tic software is ever made, I would vote for adding an extra mode for analog input, on top of linear/quadratic/cubic: this would be “piecewise constant”, where the input voltage range is split into a number of ranges, and in each range the output speed can be specified. I may be the only person who would vote for such a feature, but I thought I would cast a vote just in case :slightly_smiling_face:.

Thank you again for your help, I will buy the Tic!

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