Messages

1

SmartBOB controllers and dedicated accessories / Re: PMDX 424 E-Stop & Fault actions... similar to PMDX 126?

« on: April 08, 2017, 03:16:06 PM »

Great explanation, thanks Steve!  It make sense for safety, and it seems like PMDX makes E-Stop and /Fault connections as straight forward as possible. 

I just need a little logic to invert the upside-down Fault signal from ClearPath motors,  and fix the issue that ClearPath also asserts Fault any time a motor is not enabled (which would keep PMDX & Mach in E-Stop forever). 

Kudos: This would be more complicated without PMDX E-stop/Fault 50ms filtering? Otherwise sequential logic would be needed to eliminate ?runt? Fault pulses due to the delay between Enable and HLFB signals.

I??ll clean up my schematic for this circuit and post it? may be useful to somebody else using ClearPath servos.

Ray

2

SmartBOB controllers and dedicated accessories / PMDX 424 E-Stop & Fault actions... similar to PMDX 126?

« on: April 04, 2017, 08:36:05 PM »

Drinking in Manuals and Forum posts! The PMDX 126 BOB manual provides some great detail on input actions and filtering in section 6 that I can't seem to find in the 4xx SmartBOB manuals. I'm wondering if the 424 acts similarly, particularly on E-Stop and Fault.  Please point me elsewhere if I'm missing something! 

A couple specific questions on the 424:
 
  1. Is Fault filtered and captured after ~50ms as with the 126, and is that when all outputs (incl. motor enables) are disabled AND Mach4 gets the report?
  2. Are (a) outputs re-enabled on-board if Fault is de-asserted, or (b) does the 424 wait for Mach4 to restart things?
  3. If 2(a) is true, is there any concern about, say, an unintended spindle restart or axis movement, independent of Mach?

Thanks in advance... This will help me design the interface between the PMD 424 Fault input and my 3 servo Fault Outputs.

Ray

3

General Discussion / Re: Connecting ClearPath Servo HLFB signal to PMDX 424

« on: April 03, 2017, 09:34:05 PM »

I've tested and confirmed that ClearPath servos de-assert HLFB on a servo fault or anytime ENABLE is low. That suggests some questions assuming de-asserted HLFB asserts the PMDX /FAULT input.

1. Does the 424 immediately (on-board logic?) disable outputs (including motor enables) on an E-Stop or Fault?
2. Is there a minimum pulse length for E-Stop or Fault (like ~50ms on PMDX 126)?
3. Will Mach4 enter E-Stop after a Fault Assertion?
4. When restarting after E-Stop or Fault, will outputs be re-enabled if Fault is still asserted?

I'm guessing (4) is a "no" and the rest are "yes", and if so I'll need a way to clear the Fault input before attempting to restart Mach. It may require gating HLFB with the motor Enable so Fault is asserted only until Enable drops.

I'd like to open my servo and VFD contactors on a physical E-Stop, but rely just on enables dropping quickly on a servo fault.  That allows the servos on-motor LEDs to be checked for an error code, otherwise the fault cause is unknown.  Any thoughts here will be appreciated.

4

General Discussion / Re: Connecting ClearPath Servo HLFB signal to PMDX 424

« on: March 30, 2017, 08:44:53 PM »

I went hunting for more data on the 4404.  I found a sample circuit on the data sheet that shows the input tied to a 4469 with a 12V output... so it looks like inputs up to Vdd are fine.  (Also, the 4469 is an interesting logic/driver choice for HLFB... similar specs to 4404, 4 drivers in one chip, and gated inputs). But I still like your idea of protecting the inputs with a simple voltage divider!

HOWEVER, I just noticed HLFB shows "fault" (i.e. stops conducting) any time a motor is NOT enabled... not just on a real Fault.   Wondering if this is OK with the PMDX 424 and Mach4?  Maybe enable never gets set because Estop/Fault is set, and we are stuck?? I'm out of my depth here!

If this is a problem, we can use Steve's earlier alternative: make a script, hook HLFB to a normal input, but only look at it when we are running.   Or maybe use the AND-gated 4469, and wire it so that FAULT = (ENABLE) AND (NOT HLFB).

5

General Discussion / Re: Connecting ClearPath Servo HLFB signal to PMDX 424

« on: March 29, 2017, 04:00:03 PM »

Appreciate the feedback!

Yes, I couldn't figure a simple way to put HLFB's in series with their voltage drop.  But I'm thinking that the parallel connection of several 4404 open-drain outputs gets around that.... any single or multiple motor fault will cause the /FAULT input to pull to ground.  The paralleled outputs may not show up well... at the top of the diagram.

I checked the 4404 datasheet again, and while it says "TTL/CMOS compatible", I didn't think there is an issue as long as Vin is less that Vdd and the gate is internally diode protected to stay below VDD.  (But if there is an issue, your series resistor (voltage divider) could get us down to any desired hi-state gate voltage).

Am I misunderstanding the 4404 data sheet?

6

General Discussion / Connecting ClearPath Servo HLFB signal to PMDX 424

« on: March 27, 2017, 12:10:20 AM »

ClearPath servos will connect directly to a PMDX controller for step, direction, and enable outputs.  The problem is the HLFB signal from the motor is active (on) when a motor is happy, and off when it faults.  The /FAULT input on the PMDX 424 (or 416) needs to connected to the isolated ground to indicate a fault, just the opposite of the HLFB output. Steve Stallings suggested possible solutions in this forum last fall... a relay might work, but the ClearPath HLFB is limited to 30v and 9ma, and that is non-inductive. Plus, you've probably got 3 or more HFLB signals to connect to /FAULT. Has anybody done this?

I've been checking out solid-state solutions, and it looks like the TC4404 driver chip might be a good choice. It's an inverting open-drain MOSFET driver, and you get two of them in an 8-pin IC for about $3 from Digikey, Mouser, etc.  Two of them plus 4 resistors will handle 4 motors. I haven't tried it yet, but I think the hookup shown below will do the job.

I'd appreciate thoughts from Steve and anybody else on this approach... and any problems with the design.

Ray