servo control

[bobkeyes]

I have a Pololu serial 8, servo controller. I am using the MiniSSC plugin. I can only move the servos counter clockwise and then back to 0. I have not figured out how to move the servo the other way.

Can anybody shed any light on this?

[bobkeyes]

Nobody with any ideas??:confused:

[Aurbo99]

what are your control commands for the miniSSC plugin?

if you can only control counter clockwise and only back to zero, perhaps a negative command will result in a clockwise motion.

I've not played with the plugin and thats why I asked.

If it uses 90,180,270,360 degree commands then try -90,-180,-270 -360

[bobkeyes]

Thanks Steve for the response. But, I am only using the plugin. I sequence just as I would for lights. If I use intensity at 100% then I get a 90 degree motion counter clockwise. Lowering the intensity decreases the movement. ie 50% is about 45 degrees. Can't get it to move clockwise.

Thanks again.

[Aurbo99]

I'll poke at the plugin and see if I can figure out the method used and tinker with it.

[bobkeyes]

Thanks Steve.

[David_AVD]

I haven't played with RC servos for a couple of years but...

Depending on how they're being driven, having only positive control values can be correct. The "neutral" position may be 50% as a control value. It all depends on how the software and hardware has been implemented.

Move the servo throughout it's range via the software and see how that compares with the servo's specs. ie. If the servo moves 90 degrees and it's a 90 degree servo, then you'll have to use a 50% control value at the neutral position.

If it actually only moves 90 degrees but you are sure that servo is spec'd for 180 degree operation, then something may be amiss. Different servos have different rotation ranges so you need to be sure what you're dealing with. Does that make sense?

[CarlRay]

Standard RC servos only have 180 degrees of travel. I am using a Parallax servo controller and in Vixen, "0" cell intensity, positions the servo all the way to the one side, which is zero degrees. "100" cell intensity, positions the servo to the 180 degree side of travel. You can move the servo to any position in between by specifying a cell intensity of 0 to 100 percent. If you can move your servo from zero to 180 degrees and back again then everything is working fine. The servo will not go beyond these limits as there are actual hard stops inside the motor to prevent this and in fact, trying to hold a position while against the stop can damage the motor. Standard servos can however be modified into what they call a continous rotation servo and these can actually be purchased already modified. Once they have been modified, they are no longer "positioning" servos, they are now "speed controlled". I have not tried a continuous rotation servo with Vixen so I can not say what they would do.
Hope this is somewhat of a help to you.

Carl

[bobkeyes]

Carl and David,

Thanks for the response. If I unplug the servo I can physically move it 180 deg. But, I can't get that movement under power with the Vixen software. I can send byte commands to it and move it through the entire range.

[David_AVD]

Sounds like a plugin issue then.

[Aurbo99]

Still tinkering with it.