Hey all,
Starting a project in which I would like a servo motor to rotate freely until a torque cell gives feedback and the servo is stopped. Then want to record the angular position of the servo at that moment. I was going to utilize a rotary encoder with a servo, but I’m not sure I can have the servo freely rotate as that’s not what servos do…any help let me know
Based on your description, it does not sound like the servo will actually be providing torque? If so, you only need a 360 degree sensor. An encoder is only effective if you zero the position first, or have some way of reading a specific angle.
If you do need to power the servo, or if we did not correctly understand the need, can you clarify?
We will be providing torque with the servo on a limb, as the torque cell reads the torque in the limb and it reaches a certain threshold, I would like the servo to then reverse direction. In the moment that the torque reaches threshold, I want to know what the angle of displacement from zero is.
Thank you for clarifying. What is the max torque you need the servo to provide and what is the total angle of travel? Are you open to using smart servos as opposed to RC servos?
The servos will be used on rat limbs, so the amount of torque needed is fairly low. The angle through which I would like the servo to sweep is about 180 degrees in its entirety. No experience with servos so I don’t know what the difference between RC and smart servos is
This seems perfect:
robotshop.com/en/analog-feed … RB-Ada-199
It’s small and has a separate feedback line for position.
It rotates 120 degrees (uncomfortable if you force the rat’s leg back onto itself).
Another option with analog feedback:
robotshop.com/en/analog-feed … RB-Ada-200
Thanks so much!
I had one more question…how accurate is the position feedback on these servos? I need accuracy close to the .5 degree range.
Unfortunately our supplier does not provide that information, but the output is likely directly from the onboard rotary potentiometer, so it will depend largely on the accuracy of your microcontroller’s ADC. If you have anything above 8-bit, you should be fine.
