SERVO

Question

Hello,

I have a constant fluttering of servos connected to servo board : is it possible to have a dead zone (or stabilize the pulese sent to the servo when no command is set)

I have tried with several brands and types of servos but it is always the same

It is a pity because the index of the trim indicator is always moving a few millimeters with no command !

Thank you

Phil

Answer 1

1. The servo has quite small range of separate "steps" - in theory up to 2000 steps (microseconds of pulse width), in real it can be as low as  200-300 "stable" positions, depending on your servo power quality and electrical noise (you should always have a stable power supply for servos)

2. The HCSCI plugin limits the data for the servo in 2 microsecond increments to avoid excessive unnecessary data transfer, so the maximum range is about 600-1000 positions.

3. The trim parameters are mapped from -1.0,1.0  to the servo calibrarted range (say 600-1800), it's about 600 "stable" positions and it should be beyond the fluctuations in AP mode.

Also, the HCSCI servo firmware works in such a way that when the servo is not receiving any data from the plugin for a second it stops in the last position.

So, if your servo is fluttering, it can be if the data is changed and arrived, or because you have the powering/noise issue described above).

As an option you can try to use the WitMotion driver instead of HCSCI driver, taking in account the notes about powering too.
Vlad

Answer 2

Q: I bought these ....  - 360 Degree Continuous Rotation Servo 9g for Robotic Helicopter Airplane Boat because they claimed 360 degree rotation...  How can I use them?

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Continuous servo"   is not a servo actually. You can not use it as servo.
The sellers of this device often mislead people saying that it's "360 degree servo".

The servo is a device with negative feedback, which is a potentiometer on the motor shaft. This pot defines the "reference" pulse length in the servo circuit and this pulse is constantly compared with the input signal (control pulse length) to stop rotation when they are equal.



In the "continuous" servo there is no pot, there is only a fixed resistor, so the input signal only defines the speed of rotation (CW or CCW), not the angle.  Such servo can be used only as speed controlled motor for some car models, for example.

Read more on this page.

Vlad