Servo Drive problem

[Tks]

I have a setup in where i use several Panasonic MHDA 1Kw servo drives.

as NC is use a setup with Mach 3 and the dspMc control.

Now the problem. The panasonic manual scheme states that pin 25 = GND
(you can see the internal Earth / deck symbol. Problem is that when i connect up my installation the motor starts reving up to approx. the speed for 1 volt. i discovered that the ground of the drive lies 1 volt ahead from the analog ground. So my analog output = 0volts. (even whit analog disconnected i see that volt). Now the scary thing, when i turn the motor, i can see in mach 3 that the pulses are seen, but on my scope i see on the ground channel the encoder levels! i have triple checked the wireing and i do use pin 25 = ground (GND).

When i short this lead to GND from the dspmc supply the drive almost comes to an standstill. Problem is that i cant untherstand where the encoder signal comes from.

Anyone any pointers?

[hub]

Where have you connected the scope? Between GND and ?
Have you tried connecting all GNDs (0V) together so all are at the same 0V?

[Tks]

Thanxs for your post,

I joined all the GND together and disconnected the GND from Earth.

Now every drive only needs a offset of -21 to stand still when not in PID but enabled.

So i think the problem was that earth was connected to GND and GND not enough to drive gnd's.

[hub]

You're welcome, sounds like you got it working

Yes, all the devices in any system connected together needs to have the same 0V level. But GND's do not 'drive' GND's, they just simply need to be at same level (Connected together). The 'drive' is between say +12V and 0V, could be for example a transistor.