Servo Runaway

[bgolash]

Hi

Need some troubleshooting help. I just converted my x axis to servo. All was fine until I turned on the system for a second time. At that point the servo took off on its own. I then pushed up on the (con-lc5) connector flexing it upward and the motor stopped and all seems normal. Do you think its a bad connection inside the con-lc5 or the encoder. This looks to be a dangerous condition I`m hoping for some ideas to make this setup bullet proof. I`m using a us digital encoder and their 5 pin locking connector.

Thanks and Regards, Barry

[Bloy2004]

....hard to say. Just moving the connector could have been enough to jiggle the wires and make a connection on down the wires....unless you have them secured well. It looks like you may have a bad connector. But, there could be a defective pin in the encoder head. check each wire from the other end of the connector and find test points right near the encoder head, If you find an open circuit on one of the pins(if you can get the probe in there) at least you know which wire is giving you problems. Is the encoder aligned properly?
Those pin recepticles in the connector may be expanded and have ceased making a tight connection....has the self-locking connector been pulled off without releasing the lock(if there is one)?

It's these situations why E-stop buttons are installed on machines.

[mgamber]

Originally Posted by bgolash Hi Need some troubleshooting help. I just converted my x axis to servo. All was fine until I turned on the system for a second time. At that point the servo took off on its own. I then pushed up on the (con-lc5) connector flexing it upward and the motor stopped and all seems normal. Do you think its a bad connection inside the con-lc5 or the encoder. This looks to be a dangerous condition I`m hoping for some ideas to make this setup bullet proof. I`m using a us digital encoder and their 5 pin locking connector. Thanks and Regards, Barry

Sounds like a bad wire...

[Kookaburra]

Generally it means that either your A or B chanel is not present, either it is your wiring or a bad encoder. If the motor is running then your DC volatage is fine, if your A and B chanels do not match your + and - DC voltage then the drive should (depending on what you are using) go in to fault condition and stop the axis moving. My bet would be the plug.

[NC Cams]

Servo is merely a DC motor (assumed for discussion purpose).

It runs in one direction or other until the encoder tells the driver it reached where it was supposed to go.

Loss of feed back tells amp that motor hasn't gotten there yet so it runs away until it fry's or hits limit switch or e-stop is pushed.

Some driver systems check for motor rpm, current, etc AND encoder motion - if proper relation does not exist, a shutdown occurs.

High probability is that you lost feedback due to connector/wiring issue as denoted by "jiggle fix".