Servo Motor Control From a simple switch input

Robotics
1

Hi, I have a project which requires (on a switch being activated) for a motor to rotate a load (a small LCD screen) 180 degrees and stop, then on deactivation of the switch to return to the original position.

I have done this using a normal motor with a planetary gearbox and limit switches, but the issueI have is if the load is touched (or pushed to be more precise) by an outside force it strips the gearbox. Having now replaced three gearboxes I feel it is time to move-on and use a stepper motor to drive the load directly. I am hoping that if the load is pushed it will ‘give’ and then re-align itself via feedback from the stepper motor and return to it’s correct pre-set A or B positions.

Can anyone help direct me as to which products are suitable for this set-up.

Many thanks.

2

Have a look at our Servo Trigger, I think that will do what you’re looking for. These only allow for a maximum of 90 degrees travel but if you setup your linkages right, you should be able to get 180 degrees.

https://www.sparkfun.com/products/13118

3

Hi TS-Chris, many thanks for your reply. I note that the product you refer to is a servo trigger and not a stepper motor trigger. Am I correct in assuming that a stepper motor will strip it’s gearing if manually forced to turn, whereas a stepper motor will move freely and then return to the correct position set by the ‘instructions’. As stated in my originalist this manual movement is a real possibility and has resulted in the stripping at least 3 planetary gearboxes so far.

If you could confirm that a stepper motor (over a servo) is the correct way to go I would appreciate it.

4

Just realised as I pressed SUBMIT that the header to this thread has been incorrectly stated as Servo, should have been stepper - sorry my mistake.

5

If your stepper has a lot of torque, you could strip gears. A lot of stepper driver circuits allow you to vary output current to decrease torque, if you can find a happy ground where you have enough torque to drive your geartrain but not strip the gears out when they stall, that would work.