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General Mach Discussion / Re: Mach 3 Y axis dc servo router jerks or jumps after running for a few cycles
« on: June 03, 2008, 12:38:32 PM »
Hi, I am new to this forum and ran across your query. It has been a while since you posted, so I hope you have found a solution to your problem. But, if not, it is similar to one that I have had, and solved.
I, too, tried swapping out components, initially to no avail: servos, Geckos, output ports...nada. Assuming nothing, I went back to basics and analyzed the system. There was one component I hadn't swapped - the wiring between the Gecko and the servo. Rather than rerun the wiring (internal to the table) I checked each connection with an ohm meter. It all checked out until I ran the cable shield. I noticed that the shield was not connected at either end; it was open through the DB9 connector on the controller chassis. I rewired the DB9 to include the shield and grounded it to the common ground inside the controller chassis. All the servo cables were this way, but only one channel exhibited the problem (it was the longest cable run). Note: to avoid a ground loop, the shield should only be grounded at one end. Leave the servo end unconnected.
This solved the problem. Random noise was getting to the Gecko via the cable. Grounding the shield lowered the noise to below that of the servo signals.
Hope this helps.
I, too, tried swapping out components, initially to no avail: servos, Geckos, output ports...nada. Assuming nothing, I went back to basics and analyzed the system. There was one component I hadn't swapped - the wiring between the Gecko and the servo. Rather than rerun the wiring (internal to the table) I checked each connection with an ohm meter. It all checked out until I ran the cable shield. I noticed that the shield was not connected at either end; it was open through the DB9 connector on the controller chassis. I rewired the DB9 to include the shield and grounded it to the common ground inside the controller chassis. All the servo cables were this way, but only one channel exhibited the problem (it was the longest cable run). Note: to avoid a ground loop, the shield should only be grounded at one end. Leave the servo end unconnected.
This solved the problem. Random noise was getting to the Gecko via the cable. Grounding the shield lowered the noise to below that of the servo signals.
Hope this helps.