Encoder Wiring on Mesa 7i77 board
06 Sep 2016 05:43 #80064
by jwsigler
Encoder Wiring on Mesa 7i77 board was created by jwsigler
I am progressing on my retrofit, but have hit a stumbling block on getting my encoders to work. The system is a Tree Journeyman 325 which I am retrofitting using a Mesa 5i25/7i77 setup. I can get the servos to react through Linuxcnc and move the table a little, but I instantly get a following error and the DRO does not show any movement of the axis. My guess is that I do not have the encoders wired up correctly even though I wired the encoders exactly how they were previously wired, which may be the problem.
Following is a schematic of the encoder wiring from the original mill setup.
As can be seen, the Negative Marker wire was not hooked up on the original mill system so I did not hook it up on the new system. I assume it would correspond to /IDX0 on the Mesa 7i77 board and maybe it does need to be wired in. I also noticed that some of the wiring pairs have resistors across them. I left these alone, but maybe I should have removed them. My next step is to use a voltmeter to test some of the wiring pairs as describe in one of the other forum posts, but if anyone can tell me whether I need to hook up the Negative Marker wire and whether I should remove the resistors across the wiring pairs as shown in the old schematic, that would be appreciated.
Thanks.
Following is a schematic of the encoder wiring from the original mill setup.
As can be seen, the Negative Marker wire was not hooked up on the original mill system so I did not hook it up on the new system. I assume it would correspond to /IDX0 on the Mesa 7i77 board and maybe it does need to be wired in. I also noticed that some of the wiring pairs have resistors across them. I left these alone, but maybe I should have removed them. My next step is to use a voltmeter to test some of the wiring pairs as describe in one of the other forum posts, but if anyone can tell me whether I need to hook up the Negative Marker wire and whether I should remove the resistors across the wiring pairs as shown in the old schematic, that would be appreciated.
Thanks.
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07 Sep 2016 02:52 #80109
by jwsigler
Replied by jwsigler on topic Encoder Wiring on Mesa 7i77 board
I do not know why, but there are resistors across some of the wiring pairs. It may not show in the schematic, but as can be seen in the following photo, there are resistors between 430 and 437, 432 and 437, and 435 and 437.
There are similar resistor pairs on all three sets of axis encoder wiring. I am hesitant about removing things like this because there must have been some reason for them in the first place. I had diodes mounted across all the coil terminals on my relays and eventually I found out that those were required as flyback diodes. Luckily I read about flyback diodes and knew not to remove them. I do not know if these resistors are something similar and that there should be resistors across all these pairings. Apparently each of these resistors ties the A channel, B channel, and the Marker (index) channel to the positive 5Vdc. I am hoping someone skilled in electronics can tell me if these are necessary, adn if not, would they be a reason why my 7i77 board does not appear to see any of the encoders. Of course these were required for the old Dynapath controller to work. I just do not know if they are required for a Mesa 7i77 to read my encoders.
There are similar resistor pairs on all three sets of axis encoder wiring. I am hesitant about removing things like this because there must have been some reason for them in the first place. I had diodes mounted across all the coil terminals on my relays and eventually I found out that those were required as flyback diodes. Luckily I read about flyback diodes and knew not to remove them. I do not know if these resistors are something similar and that there should be resistors across all these pairings. Apparently each of these resistors ties the A channel, B channel, and the Marker (index) channel to the positive 5Vdc. I am hoping someone skilled in electronics can tell me if these are necessary, adn if not, would they be a reason why my 7i77 board does not appear to see any of the encoders. Of course these were required for the old Dynapath controller to work. I just do not know if they are required for a Mesa 7i77 to read my encoders.
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