PSC Question

crgwbr

"All servos driven simultaneously all of the time. 180 degrees of rotation."· This setence is in the PSC documentation.· Does this mean you can't request to move 1 specific Servo?· The reason I ask, is, I'm thinking of building a robotic arm, and figured I'd use this (so I wouldn'd need 5 I/O Ports, one for each axis).

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Tom Walker

This has more to do with the nature of servos. In reality, all typical servos must be driven all of the time. Without their 20 ms control signal, their output shaft can easily be turned...in other words, they won't hold their position without constant updates.

So, yes, you can address only one servo if you wish, but all of them will be "controlled" to hold their last requested position without any further intervention from you.

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Mike Green

This sentence describes the general capabilities of the PSC. In other words, it allows you to vary the servo control pulse width over a range corresponding to 180 degrees of rotation and it can simultaneously control up to 8 servos. You normally send a command to the PSC with the pulse width for a specific servo, but it will continue to maintain the positions of up to 8 without further attention. In other words, you normally request the PSC to move 1 specific servo. You can immediately request it to move a different servo, before the first has completed its movement. If you were trying to control 8 servos with a Stamp, you would have to continuously (roughly every 20ms) send a control pulse to all 8 servos, one at a time. That might take the whole 20ms cycle period (8 * 2.5ms) leaving no time for anything else. Using a PSC avoids this.

crgwbr

Thanks

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