Hi Matt,
2010/2/2 mattschinkel <[email protected]> > > 20ms between each pulse.. Yes, I would agree that this is good timing, > but it could be selected by the user to free up cycle/cpu usage. This > timing could be more and the servo will work fine but will eventually > loose tourqe. All libs should use 20ms as a default value. My radio > reciever does output a pulse each 20ms. Shorter time between each > pulse should not be selectable since you say it may hurt the servo. > 20ms is a standard from eveything I could read about servo. I think it could shorter, like say 18ms, but sticking to 20ms seems to be a reasonable choice. > > I see on my radio reciever an analog like pulse width. I say this > again, It looks like servo's are analog devices. My radio reciever > does not output steps, it outputs a analog like pulse width movement. > If you want accurate steps, you should use a stepper motor. Do you > agree Joep? > Servos can be analog, like the traditional one you can find on RC plane, those that can be found at a decent price. Servocs can also be digital, like Dynamixel AX 12. Driving a analog servo requires you send some pulse, every 20ms between 0.5ms and 2.5ms. Driving a digital servo requires... well it depends but usually digital servos are linked between them on a bus, and you have to send special command frames over the bus (RS485 for AX12 IIRC), and the servo itself will interpret the command and move accordingly. You can get feedback information with digital servos (torques, angle, speed,...) So, yes, here we're talking about analog servos. > > For the sake of a library, I say we should not go by 10us steps, we > should simply make sure the pulse width is between 250us? to 2.5ms and > have as much resolution as possible. Lower oscillator speeds will have > less resolution (such as 20us steps) and higher osc rates will have > higher resolution (maybe 5us). > Please be sure you library is able to deactivate a servo, that is, not send any pulse at all. I have a MIC800 servo controller (PIC behind the scene), which costs me an arm, and I can't turn off a servo... Cheers, Seb -- You received this message because you are subscribed to the Google Groups "jallib" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/jallib?hl=en.
