Strange behaviour of "set max speed" command with TIC 36v4

Hi, I have been using the Tic 36v4 with serial control for moving objects up and down on a theatre stage for over a year. Firmware is 1.0.8. It works fine, but I noticed the following behaviour when trying to change the speed while going to a target position:

  1. I send a “set target position”.
  2. While the Tic is going to that position, I modify the speed by sending “set max speed” commands.
  3. It works fine when I increase the max speed.
  4. If I reduce the max speed, nothing happens, it just continues with the previous speed until I send a new “set target position”.

I solved my problem by modifying the program using “set target speed” commands instead of “set target position” . That works but results in a slightly more complex program.

Any idea why it is possible to increase max speed but not to decrease it while going to a target position?


The way the firmware is currently written, the behavior you described is the expected behavior; the new max speed will only take effect after the motor’s current speed slows down below it for any reason.

Could you post some more details about what you’re doing, and why you need to use different speeds while traveling to a target position?


Thanks for the explanation. I misunderstood the sentence *"…while maintaining the speed/acceleration/deceleration limits… " in section 5.1, (motion parameters) of the user manual, thinking that you may change max speed while travelling to a position.
The background is that we have objects moving up and down on a theatre stage. Rather than moving them at a constant speed, we create a better visual effect by slowly modifying the speed. The way I do it now is by using the “set target speed” and “get current position” commands which works fine, so the problem is solved. Another way which also works is to break up the total movement in shorter sections and modify the speed for each section.
Being able to modify the max speed (both faster AND slower) in “set target position” would have been simpler but is not critical. Kind regards, Lucien.

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