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Eric
03-28-2008, 07:21 AM
Ok, brain storming here... here's the goal...
Set up a scenario using phidgets servo controller so that the voltage going to the servo is also adjusted.
Now for the more detailed background. Currently the way I've been using the servos, the servo is at a set position and holds it there. (assuming the servo is engaged.) If you try to move the servo arm by hand while it's engaged, the servo will resist and try to lock on the current position. Remove the power to the servo and the servo arm is much easier to move (obviously). What I am looking to do is allow the servo arm to be manually moved but when a certain signal gets added, ratchet up the voltage to make the servo arm resist more and more (until full voltage is applied) For instance: the servo will start at .1 volt. (manually moves easily, little/no torque on servo arm) When directed to, increase the voltage to the motor so the torque increases in the servo.
I believe there are motor controls that do this, but what about servo controls (especially in the phidget world)
Ok.. now for your ideas! Got an answer or a work around? let me know! Thanks in advance!
Eric

Alex
03-28-2008, 10:43 AM
You're going to have to splice into the power cable going directly to the Servo though. Controlling the voltage going into the board will make no diff.

This is pretty damn cool though Eric! I never really thought about doing this till now. As far as regulating voltage, I'm sure there are ways of doing this, but I'm no EE guy, so I'll let the pros answer this.

LinuxGuy
03-28-2008, 11:47 AM
For instance: the servo will start at .1 volt. (manually moves easily, little/no torque on servo arm) When directed to, increase the voltage to the motor so the torque increases in the servo.
Servos have minimum as well as maximum voltages. You have to start at the minimum (usually 4.8V or 6V) voltage and go up to the servo's maximum voltage. Servos won't move until they get their minimum voltage.


I believe there are motor controls that do this, but what about servo controls (especially in the phidget world)
Ok.. now for your ideas! Got an answer or a work around? let me know! Thanks in advance!
Eric
As was pointed out by Alex, you are going to have to splice into the power lead for the servo if you want to control the voltage going to it from a microcontroller (controlling something like a digital potentiometer) by or manual control (potentiometer).

There may be other and/or easier ways to do this, but I can't think of any offhand at the moment. I'm no EE either.

8-Dale

Eric
03-28-2008, 12:30 PM
Thanks for the suggestions!
I think I will try out your advice on the potentiometer to see how well it can work. Even though it's manual, it will allow me to see how well it will work before taking the next steps. I will post the results I find once I try it.
If anyone else has ideas, let me know!

Adrenalynn
05-09-2008, 08:39 PM
This is old, I know, and you might have abandoned it. It's just the most recent thing in my unread list. ;)

Torque = Amps, Volts = HP.

What you're asking to do is basically keep the motor at a lower stall torque continuously. You can do this, the current draw will be high, and the life of the servos will be rather short...

How about pulsing the servos at differing frequencies instead?

Eric
05-12-2008, 08:32 AM
Thanks Adrenalynn,
I haven't had time to try the previous approach. I like your idea! Very interesting. As I progress with my list of tests, I will add this to my list of things to try out.
Thanks!
Eric