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I'm not too surprised. The datasheet for these servos indicates they use pulse widths from 0.5 ms to 2.4 ms to go 180 degrees.
I have a couple of these servos and the standard 1-2 ms pulse width doesn't give a full 180 degrees.
So the datasheet I found was wrong. Thank you.
I have a question regarding this kind of motors. I am using my Raspberry Pi with the RPi.GPIO library. I have 4 of this motor, I have tested 2 and both of them worked as I write below.
On thier datasheet it is written that I can control them with a signal which frequency is 50Hz and the voltage is around 5V.
Also on the datasheet the -90° rotation needs 1 ms pulse, which would mean that, the duty cycle should be 5%. This works perfectly.
On the datasheet the +90° rotation needs 2 ms pulse, which would mean that, the duty cycle should be 10%. This doesnt works. The +90° rotation is at around 20% duty cycle.
This is the datasheet I found: http://www.ee.ic.ac.uk/pcheung/teaching/DE1_EE/stores/sg90_datasheet.pdf
Are the motors wrong, or did I understand something badly, or the PWM on the Raspberry Pi is this bad with that library? (I have read something back then it is not the perfect library for motor control)