Wiring a Chinese servo to a 7i77. Setup for yet another newbie
I've only ever dealt with stepper systems and mach3 so this is all a big step.
Ive got my servo drive connected and setup (super basically at this point, no tuning yet) and can supply it +-10v and get rotation. There's a 60 rpm or thereabouts drift at the moment but i wont worry about that untill ive got the drive enable handled by linuxcnc and the loop closed.
I'm a bit lost on the mesa pins for the encoder vs the servo drive encoder outputs. The 7i77 lists, as cut straight from the manual:
TB3 PIN FUNCTION DIR
1 QA0 TO 7I77
2 /QA0 TO 7I77
3 GND FROM 7I77
4 QB0 TO 7I77
5 /QB0 TO 7I77
6 +5V FROM 7I77
7 IDX0 TO 7I77
8 /IDX0 TO 7I77
and so on for each encoder. My servo drive speed/torque wiring details an A,B and Z +- signal wire and a 'Z collector open circuit output' and ground.
You can see the wiring diagram listed on page 24, link here.
I need a bit of help getting everything wired correctly. I've read a bunch of build and setup posts and there's enough references to burnt boards to make me cautious. Probably more an issue for the field and signalling wiring but I'd still rather go at it armed with half an idea.
Any help greatly appreciated.
Also +-10V from Mesa to pin 25 and 13 respectively .
SPH wrote: TB3 PIN FUNCTION DIR
1 QA0 TO 7I77 PA+ pin 20
2 /QA0 TO 7I77 PA- pin19
3 GND FROM 7I77 GND pin 1
4 QB0 TO 7I77 PB+ pin 18
5 /QB0 TO 7I77 PB- pin 17
6 +5V FROM 7I77 do not connect
7 IDX0 TO 7I77 do not connect
8 /IDX0 TO 7I77 do not connect
Drive enable from Mesa to pin 29 and 9.
Or I guess more to the point I obviously don't quite get the A,B,Z encoder outputs. I'll read up a bit.
Regardless, I should now be able to get the drive wired to the 7i77 and start trying to get things moving on the bench.
I've got TB5 pin 4 (AOUT0) going to pin 25 (VREF +) on the drive and TB5 pin 3 (GND) going to pin 13 (AGND) on the drive as suggested.
The drive isn't (wasn't) enabled when I connected the plug.
When the drive plug is connected I read 4.8v between pins 3 and 4 on the TB5 connector and if I enable the drive it runs at something like 750rpm. As you'd expect, i guess, for an output of 4.8v. If I disconnect the TB5 plug the pins go back to 0v.
Anyone have any insight on those drive pins? I don't know if I've actually found the issue or just a way to make it not crash. As it is now I've got pin 25 from the drive going to TB5 pin 3 and 13 to TB5 pin 4.
Lucky the board seems to have been able to handle it.
Now that the wiring is around the right way with no wayward voltages everything is working nicely!
I have a motor that's actually tuned half ok! I've only had to change one parameter in the drive and that was to put it into speed control which is quite a surprise, don't know if it's a fluke or what but all I've had to do is connect it and tune via the calibration screen. Just a bare motor mind you, it might be a different story once everythings connected up.
One thing that's struck me with the HAL scope and watching the DRO now the first servo is connected is just how damn instant everything is. I'd always hated how mach3 felt like you were driving it with a pole, always seeing things after they happened.
It's awesome being able to put my hand on the motor shaft and see the few tiny vibrations I've still got reflected in the DRO.
Still a long way to go, I'll likely have a lot of things to change once I get the motors in place and can actually tell which way they should be turning and put some load on them but all in all a far better end to the day than it was looking like a few hours ago.
Oh! I'm still not confident I know how to hook up the drive enable. If someone could spell it out for me I'd really appreciate it. For someone who considders CNC a favourite hobby, basic electronics still catch me out often enough.
Pretty sure I need to send +24v to pin 9 on the drive and - to pin 6? The answer will seem really obvious in the morning no doubt.
Thanks again all.
Take a multimeter set it to OHM ( usually 200 ) or to test for shorts with a buzzer if it is an auto DVM, connect the probes to those two pins and check if it enables the drive. Check the polarity of the probes when it enables and wire them to Mesa accordingly.