Actually 360 degree Continuous Rotation Servers are quite common. There are basically two types of servos: 360 degree Continuous Rotation and 90 degree Standard Rotation. Each has a different purpose.
As far as manufacturers not providing datasheets for their products, I would suspect this depends on where you are purchasing the servers from. If you stick with manufacturers such as Hitec, Tower, Futaba, or Parallax you should be fine. If you are purchasing cheap off brand servers, then you may run into an issue with each being different as far as how they react to a PWM signal. Also, depending on the application, there could be a difference between plastic and metal gears. I tend to like metal gear servos though. Cheers, Jon On Wed, Sep 16, 2020 at 8:54 AM Dennis Lee Bieber <[email protected]> wrote: > On Wed, 16 Sep 2020 07:36:14 -0700 (PDT), in > gmane.comp.hardware.beagleboard.user Pavel Yermolenko > <[email protected]> wrote: > > >I noticed that many servo motor manufacturers don't provide datasheets > for > >their products (for example for my servo it's the case) > >Generic values that can be found on the web don't work for every servo. > >For example what should be pulse width for 0/90/180/360 degrees. > >I suppose the value of pulse widths depends on a particular model. > > > > Very few servos have a 360 rotation range... +/- 90 degree is more > common (the exception being servos that have had the position feed back > logic removed and act as variable speed continuous motors). > > > https://www.jameco.com/jameco/workshop/howitworks/how-servo-motors-work.html > > 1.5mS pulse should be the "neutral" position (middle of the range). > > https://learn.adafruit.com/adafruit-motor-selection-guide/rc-servos > > https://learn.adafruit.com/adafruit-motor-selection-guide/continuous-rotation-servos > > >For example I noticed that if pulse width in quite low, the servo heats > up > >as an iron. > > Likely you are over (under) driving the position, and the servo > can not > physically move to the position you are requesting -- this leaves the coils > energized with the servo pushing against the internal end-stop. > > My suggestion would be that you write a short calibration program > with > which you adjust the pulse width from neutral, one step at a time, until > the servo reaches an end point (ie; the control "horn" stopped moving while > you changed the pulse width), then back up until you just detect the horn > has moved off the end-stop. Record that value and repeat for the other > direction. Maybe put a sticker on the servo with the values of the > end-point pulse widths -- neutral position should be the average of those > two values. > > Do that for all your servos, and either use the minimum span for > all, > or program the limits per servo (if using Python, install Adafruit Blinka > and libraries for CircuitPython -- the servo class allows override of > min/max pulse width; they default to 0.5 - 2.5ms, but do state that > "standard" servos are supposed to work with 1.0 - 2.0ms width). > > https://learn.adafruit.com/circuitpython-essentials/circuitpython-servo > https://learn.adafruit.com/circuitpython-on-raspberrypi-linux (ignore the > R-Pi, it works for BBB also) > > https://learn.adafruit.com/using-servos-with-circuitpython/high-level-servo-control > > > > > -- > Dennis L Bieber > > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/nkb4mfd0pbjeigumqjvhb0k8gur9qql2ed%404ax.com > . > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/CAG99bkpb_a%2B8RUCggcgWF-fGBcrgFY4VYGA2CEygfPTR8GM%3DAQ%40mail.gmail.com.
