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:

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.

PCW wrote:

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.

Follow up questions.  I do have both 5v and 24v supply in the cabinet.  24v was simply going to handle the sensors and pneumatic relays, and the 5v was going to handle the case fans and supply v5 logic to the mesa.  Any benefit to this vs just doing all 24v?

Is there any GOOD reason to tie the enables to outputs vs just the 5v line?
 

Hi Connor,

I see a lot of your questions have already been answered, but I thought it would be helpful for me to weigh in as well (I’m an applications engineer at Teknic).

The choice between Step and Direction vs. quadrature is up to your personal preference and your controller’s capability. Step and direction is more popular, but quadrature has more noise immunity and other technical benefits. If your controller has quadrature capability, this is what we'd recommend.

As you read in the manual, we do not recommend 5V differential signals because they don’t always reliably swing the full five volts. A lot of manufacturers publish 5V, but the signals can drop as low as 2-3V.

Worse, there's a chance they may work at first, but then over time start to become unreliable (as the environment changes, the components age, if the motor changes temperature, etc.). Single-ended is a better option.

Regarding the enable line, we do not recommend hardwiring the enable for a couple of reasons. First, if the motor ever executes a protective shutdown (e.g., you accidentally ask for too much torque), toggling the enable line is the way to clear the shutdown and resume normal operation. The enable is also a safety feature that helps eliminate the risk of any surprising motion upon power-up. If the motor is powered up but disabled, it will not accept any move commands until the user deliberately enables it.

HLFB can be configured to give you various data. Many CNC operators use HLFB configured to provide “Servo On” or “In Range” to monitor any shutdowns or lagging (due to issues with mechanics, load, excessive friction, etc.). There is more information regarding the different configurations in the ClearPath User Manual (currently pages 50-60): teknic.com/downloads/

I’m not familiar enough with the controller you’re using to recommend specific wiring, but we’re happy to help with any questions about wiring if you would like to contact This email address is being protected from spambots. You need JavaScript enabled to view it. or fill out a contact request on our website: teknic.com/contact/

I hope this information is helpful. Please feel free to contact us with any additional questions that come up.

Best regards,
Bridgette O.  - Teknic Servo Systems Engineer