ClearPATH servo with MESA 7i76e

I have a few questions with regard to theses servo's and how to wire them up on a MESA 7i76e

What is the best way to wire up these servos?  They have ability to do step/dir or quadrature. 
On the connections,  They have Input A- / A+, B-/B+, and Enable -/+   In step/dir mode A is direction, B is step.  

I just read this "Engineer’s Note: 5V differential outputs are not directly compatible with ClearPath inputs because differential drivers' guaranteed output voltage swing is typically not guaranteed to meet the ClearPath input minimum input voltage requirements. While differential drivers may work initially, they may fail over time as the environment changes, i.e. the motor heats up, components age, and so forth. This can result in erratic  operation that is difficult to debug."

So, would that mean that step/dir would be the best method using +5v with a Input -, or GND with input + vs using the + and - for said input?

Next question would be what to do with the enables, I can hard wire them into the +5v, or take them to a output.  Field I/O will be 24v, and these servo's support 5-24v  on inputs.  Anyone see any issues with mixing 5v and 24v?  Do those share the same GND?   Any benifits to having the enable wired to a output vs always enabled? I'll be using this with a X, Y1, Y2, Z gantry CNC.

And lastly, any benefit to using the HLFB output from the servo?

Thanks, Connor


 

For single ended wiring:

+5V -- > DRIVE STEP+ AND DIR+
7I76 STEP- --> DRIVE STEP-
7I76 DIR- --> DRIVE DIR-


On a 7I76/7I76E the 5V and 24V are isolated unless
the 24V common and 5V common connect externally.

That said, it probably does not matter because
If the enable has + and - inputs its fully isolated
so just needs its - input connected to 24V common
if you use a field output.

One disadvantage of using mixed 5V and 24V signals
is that a wiring mistake may damage 5V outputs.

Connor9220 wrote:

They have ability to do step/dir or quadrature. 

5V differential outputs are not directly compatible with ClearPath inputs 

So, would that mean that step/dir would be the best method using +5v with a Input -, or GND with input + vs using the + and - for said input?
 

Single-ended v Differential is not related to step/dir v quadrature. Both step-dir and uadrature can be single-ended or differential. 

It probably doesn't matter which control type you use. I consider quadrature to be a little more elegant than step-dir though. 

As for sigle-ended v differential, I am not sure that I really understand what they are saying. In general differential is more resistant to electrical noise, and I would also expect it to have a greater voltage swing unless they are doing something odd in the driver. 

Connor9220 wrote:

And lastly, any benefit to using the HLFB output from the servo?

Thanks, Connor



 

The HLFB is the only feedback you have from the servos.  If you don't use it, LCNC has no way of knowing if the servo has tripped for whatever reason and will continue moving the other axes along just like a stalled stepper motor.

There are a number of modes available, but the simplest would be "servo-on".  This could be connected to joint.N.amp-fault-in in HAL and will let LCNC know if the servo has tripped.

andypugh wrote:

Single-ended v Differential is not related to step/dir v quadrature. Both step-dir and uadrature can be single-ended or differential. 

It probably doesn't matter which control type you use. I consider quadrature to be a little more elegant than step-dir though. 

As for sigle-ended v differential, I am not sure that I really understand what they are saying. In general differential is more resistant to electrical noise, and I would also expect it to have a greater voltage swing unless they are doing something odd in the driver. 

Okay, so, I'll go with the quadrature mode.  I like the idea of it vs step/dir.

On the differential part, I'm a bit stumped on that too.  I'm going to check with them and see if they can tell me what voltage swing they're expecting, and possibly see what hardware they've tested this on.  Maybe PCW can tell us what the voltage swing is on the MESA 7i76e card.  I would much prefer to use differential vs single ended.

Thanks, I'll see about routing those to inputs and have it configured for fault mode or what ever they call it.