Netherlands
Asked

First Servo Command Triggers Movement Of Other Servos

Dear community,

I observed a curious problem and wonder if anybody has seen this before. When I start my EZ-B and operate a servo (e.g. open a panel/door) for the first time it spontaneously triggers the movement in other servo's as well (e.g. opening other panels/doors). It is only the first time. E.g. after I close all panels/doors that "mysteriously" moved the issue is gone, and I can move all servo's individual without unexpected movements by others. It is not an SW bug, no movement commands were given to servos that suddenly moved. My line of thought on what might be the issue/solution:

  1. Should I give a movement order to all servo's in the initialization routine. E.g. release all servo's or open/close them.
  2. I noticed the servo's that mysteriously move, have longer/extended cables connecting them to the EZ-B (the 3-wire cables). Maybe I should re-positioning the EZ-B to avoid the longer cables? Has anybody had similar issues and/or knows what is causing this issue? Kind regards Charel Operating my R2D2 on EZ-B


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PRO
Netherlands
#1  

I guess I can answer my own question, I did run some tests to shorten the cables (EZ-B from/to servos) and the issue is gone

PRO
Belgium
#2  

hi charel

what kind off servo's are you using ?

PRO
Synthiam
#3  

Analog servos will do that when power is applied. Maybe higher end analog ones won’t, but that’s why I prefer digital servos.

The reason analog servos twitch like that has to do with the way they work. There aren’t any intelligence in an analog servo so they merely respond with any voltage that can be interpreted as a signal. When power is applied there’s a voltage spike that they recognize as a pwm.

PRO
Belgium
#4  

hi dj

does that mean that long cables isn the problem ?

PRO
Synthiam
#5  

It’s hard to say. The capacitance of longer cables could cause analog servos to behave even more erratic. But if that fixed it for the OP, it must be true :)

#7   — Edited

I've never had a problem with long servo cables causing the behavior the OP mentions in my analog servos. I use Hitec's high end analog servos. I did have problems with them twitching or moving when power was applied. I made sure the hub was centered after the first power up as they wanted to move to their known center when powered. I also placed a min/max commend and a start up position and speed command in my INT script in ARC for each one. I dont release any servos once ARC was started and set unless they need to be for some reason.

As far as Digital Servos, I really like them for their power and less power use over analog. However I hate the way they buzz when holding a load. EZ Robot's digital servos don't buzz like the rest and have super torque.  EZ Robot HDD Servos