I know this is a stretch, especially with the limited data available. I have been trying to find a problem with a rotary encoder feedback card in a cnc control system. I will explain its function. The problem board receives position data from the rotary encoder, which is coupled to a servo motor. The encoder is received and relayed to a trajectory computer via an optical link. The trajectory computer compares the positional data from the feedback card to what it as commanded the servo amplifier to do, and makes constant command updates to control motion.
The feeback card is basically the middle link between the trajectory computer and the encoder, and also sends power commands to the servo amplifier.
What is frustrating is the board is NOT 100% bad! Once everything is powered up, the entire system is without fault and returned correct position data to the trajectory computer. When motion is commanded, some times it will move around for a minute or two without issue, then just fault out with a "feedback error" to the trajectory computer. However, I have closely monitored the position read directly at the trajectory computer expecting to see a jump or anomaly in position but that seems very stable and repeatable.
there are further feedback test routines in the trajectory computer and all return error free.
I remain confident this board is the suspect as there is a board for each motion axis and if we move that card to another axis, which will use a completely different servo/encoder/amp, the problem follows the feedback card!
Among the rack of feedback cards, there is a common optical card which is responsible for converting signal for optical link to the trajectory computer. I would almost look at it as well, but unless there is somehow a optical assignment ID (?) which would follow the card, I would think we would see other errors as well. There is also an optical link test routine and that returns no errors.
Now.....the feedback card is a very complex device, wiht 3 microcontrollers, and is a tri-level board. Making repair VERY difficult. I am curious, would it even be conceivable that a uC is glitchy or do they usually simply fail with an obvious failure mode?
I have combed the board for hours trying to find a damaged trace, obvious issue with a passive, and nothing is standing out. I can even compare to an identical known good card and all seems to test the same.
I would almost be thinking there is dirty power somewhere but all caps to ground test good, and testing what I can in the system, all AC ripple is down in the 1-3mV range.
Would anyone have any advice at all to comb this circuit? Loaded with optos, uCs, DACs, and ADCs. And I realize this is about the time to send it somewhere but there is NO ONE that works on them! So we have a very expensive machine sitting idle over this! I just want something to let the magic smoke out so we can trace it and repair it! LOL
The feeback card is basically the middle link between the trajectory computer and the encoder, and also sends power commands to the servo amplifier.
What is frustrating is the board is NOT 100% bad! Once everything is powered up, the entire system is without fault and returned correct position data to the trajectory computer. When motion is commanded, some times it will move around for a minute or two without issue, then just fault out with a "feedback error" to the trajectory computer. However, I have closely monitored the position read directly at the trajectory computer expecting to see a jump or anomaly in position but that seems very stable and repeatable.
there are further feedback test routines in the trajectory computer and all return error free.
I remain confident this board is the suspect as there is a board for each motion axis and if we move that card to another axis, which will use a completely different servo/encoder/amp, the problem follows the feedback card!
Among the rack of feedback cards, there is a common optical card which is responsible for converting signal for optical link to the trajectory computer. I would almost look at it as well, but unless there is somehow a optical assignment ID (?) which would follow the card, I would think we would see other errors as well. There is also an optical link test routine and that returns no errors.
Now.....the feedback card is a very complex device, wiht 3 microcontrollers, and is a tri-level board. Making repair VERY difficult. I am curious, would it even be conceivable that a uC is glitchy or do they usually simply fail with an obvious failure mode?
I have combed the board for hours trying to find a damaged trace, obvious issue with a passive, and nothing is standing out. I can even compare to an identical known good card and all seems to test the same.
I would almost be thinking there is dirty power somewhere but all caps to ground test good, and testing what I can in the system, all AC ripple is down in the 1-3mV range.
Would anyone have any advice at all to comb this circuit? Loaded with optos, uCs, DACs, and ADCs. And I realize this is about the time to send it somewhere but there is NO ONE that works on them! So we have a very expensive machine sitting idle over this! I just want something to let the magic smoke out so we can trace it and repair it! LOL