LabView Alternative for an Automated System to Drive Steppers andTake Measurements of the DUT.

[Klaus Kragelund]

On a sunny day (Mon, 12 Aug 2013 06:18:04 -0700 (PDT)) it happened Klaus


<[email protected]>:








In the RC servos is a small DC motor, a gear with a large reduction,

and on the shaft that sticks out a potmeter (slightly over 180 degrees rotation possible).

There is also a chip that wants an impulse form 1.5 mS wide for servo mid-range,

at least about every 20 mS or so (no pulse motor powers down).

The pulse width sets the position, smaller pulse is more left, wider pulse is more right.

As such, as the control loop is in IN the servo, I have no control over that,



wikipedia has some nice pictures of what is in it:

http://en.wikipedia.org/wiki/Servo_(radio_control)

You can see the potmeter in the picture of the blue one (enlarge).



I was trying to get that control loop to oscillate (mass of the antenna plus counter weight as load),

and actually had it oscillating for at least 2 seconds (about 1 second period time).

The way you could stop it oscillating is power down (remove pulse) I guess,

but no way to KNOW if it is oscillating, apart from monitoring the received signal.

It is an interesting thing to get that within usable tolerance.

Well, you can measure the current to the servo, you should be able to see the oscillations there.

But, I think you have chosen a too cheap and low performance servo. If you had used a better one (with less slack in the gear) or a stepper motor with gear, you could avoid the oscillations all together

Regards

Klaus