Hi guys, I noticed that my little Hobby servo at the 0° position (M3 S0 with pressure) stays there without problem when I cut the power, but I notice that sometimes it goes down to 90° (M3 S255) when the power is cut. Is it normal that the servo moves when it is not programmed to do so? If so, does it remember its position?
Servos are analog devices, so, yes the cheaper ones can be weird. It doesn't remember per se, but will move where commanded next time.
Ok thanks, I'm trying to get a perfect homing on my xy plotter. By the way i notice another thing, the grbl homing ($H) disable my servo (the pen drop just before homing start even if i say "go up" before), so the pen may trace while homing. Is it a way to prevent that? Actually it was not doing that before, weird... trying to check related issue on GitHub.
I discovered that there is a complex relationship with $30, the force applied on the servo and Homing. By reducing the force (i used 2 elastics to pull the pen down) and using $30=255 instead of $30=1000, then both issues are gone, no pen falling out when homing and when power turned off.
Ps, was mentioned in the Docs docs:blackbox:connect-rc-servo [OpenBuilds Documentation] Best to have pen only under gravity. Servos "self correct" so adding force against it, makes it work very hard to keep the motor spinning to counteract the force. Actual servo/spec depending of course. A decent servo's gearbox won't be backdriven by a rubber band, but the little 9 gram ones, well, that grams means something. Two rubber bands is more than 9 grams of force (; - thus backdriving the motor, causing the a) drop when not under software control and b) servo motor to fight hard to keep correcting the load pushing it off position
BlackBox interesting... i changed the value because i actually need only about 45 degree not 90. I use the rubber bands because the only gravity was not enougth to pull it down probably some frictions, i should check it closer. Good explanation, help me to better understand the phenomenon. Thanks
Im curious what amperage servo 5v line supports/limit? Looking thru docs but not finding many such details. Thx
Try to keep it under about 400mA if possible With an Interface connected as well, probably safer around 250mA. If in doubt measure the 5V rail, if its overloaded it will have a drop
