Servo default values?

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mwm
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Joined: Wed Aug 09, 2017 3:52 pm

Servo default values?

Post by mwm » Fri Sep 08, 2017 10:42 pm

I'm working on a Python version of the Pyboard Servo drivers, and wonder where the default values for pulse_min and pulse_max came from. I'd expect them to be 100 and 200, that being the expected values for hobby servos. Are they maybe for some specific servo?

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dhylands
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Re: Servo default values?

Post by dhylands » Sat Sep 09, 2017 12:06 am

Nominally, hobby servos expect a pulse with in the range 1 msec to 2 msec. Some will accept 0.5 msec to 2.5 msec (see some plots I did on 3 servos I happened to have: http://davehylands.com/Robotics/Servos/ ... tions.html). The values 64 and 242 correspond to 640 msec and 2420 msec which is probably what Damien measured for the servos he sells through the MicroPython store: https://store.micropython.org/store/#/products/HS-55

Even 2 servos of the same kind will have slighty different curves (the blue and pink curves in my plot are from the exact same brand/model of servo) so if you want accuracy, you really need to measure your servos and calibrate them individually.

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