Author Topic: PMDX-126 Latching eStop  (Read 2506 times)

jrbloom

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PMDX-126 Latching eStop
« on: April 25, 2021, 02:20:51 AM »
Hi
I have just wired up an estop to my new PMDX-126 based enclosure. The button works as expected on initial press. But once activated the BOB seems to latch the signal and releasing the switch dies not clear the state (led remains lit). Restarting Mach 4 clears the condition until I press again. It's as though the Bob holds the state until the own is lost.

I have confirmed that the switch us working properly. Once latched even shorting the input with a jumper doesn't release it.

And ideas what might be wrong? If the Bob really requires the own to stop is there a way to do this without restarting Mach?

Thanks

Jon

jrbloom

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Re: PMDX-126 Latching eStop
« Reply #1 on: April 25, 2021, 11:31:28 AM »
Lol ... Androids gboard helpfully corrected "PWM" TO "own" above twice 🙄

I meant to say "it is as though the Bob latches the state until the PWM is lost."
&
"If the Bob really requires the PWM to stop is there a way to do this without restarting?"

12strings

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Re: PMDX-126 Latching eStop
« Reply #2 on: April 28, 2021, 01:10:08 AM »
It has been a while since I've used a PMDX-126 board, but I *think* that if you have the PMDX-126 DIP switches set to enable charge pump, the PMDX-126 will keep the EStop signal active until it sees the charge pump signal (from Mach) stop.  So... how do you have the DIP switches on your 126 set?  If you are running Mach3, somewhere there is a setting to keep the charge pump active while in EStop.  You do NOT want that feature enabled.

12strings

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Re: PMDX-126 Latching eStop
« Reply #3 on: April 28, 2021, 01:27:13 AM »
Ahhh... just found my post from long ago about this.  See this thread (not that you are running LinuxCNC, but the PMDX-126 part pertains to you).

https://www.pmdx.com/PMDX-Forums/index.php?topic=521.0

jrbloom

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Re: PMDX-126 Latching eStop
« Reply #4 on: April 28, 2021, 06:31:09 PM »
Thank you, this does match my observations perfectly. At least I know the board itself is behaving 'normally' even if that 'normal' is not documented!

Now I just need to work out how to ask Mach4 to pause/restart the PWM. I'm very new to this, but hopefully the answer lies in an LUA script. I'll do some digging and update this thread for completeness if I find a solution.

12strings

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Re: PMDX-126 Latching eStop
« Reply #5 on: April 29, 2021, 12:54:17 AM »
Quote
how to ask Mach4 to pause/restart the PWM
PWM?  Do you mean the PWM signal that controls the spindle speed?  Or do you mean the charge pump signal on port 1 pin 17 that tells the PMDX-126 that it is OK to enable its outputs?

And lets back up a step here:  What motion device do you have connected between your computer and the PMDX-126?  A PMDX-SmartBOB?  SmoothStepper?  Some other device?

jrbloom

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Re: PMDX-126 Latching eStop
« Reply #6 on: April 29, 2021, 04:59:54 PM »
I just mean the charge-pump. For some reason my brain keeps picturing it as a PWM, and conflating the two!

I'm using an ESS. I did some trawling yesterday and noticed two things:
1) Warp9 point out that we don't really need the charge-pump at all because the ESS won't create noise on the parallel port like a classic direct PC connection
2) There appear to be controls in the pin setup of the ESS config tool to explicitly gate any output on both eStop and Machine Hold. So I should be able to set this for the charge-pump output.

I'm conservative when it comes to machinery so will probably not disable the charge pump unless I have a good reason to. I haven't had a chance to confirm that 2) above works yet. But it looks like it should, and that's the path I will likely take.

Thanks for stepping in and helping here. It's been a baptism of fire, but I'm nearly there I think.

Jon
« Last Edit: April 29, 2021, 05:04:21 PM by jrbloom »

jrbloom

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Re: PMDX-126 Latching eStop
« Reply #7 on: April 30, 2021, 10:53:30 AM »
Ok, so I tried using the ESS Pin controls to Force Charge Pump to Off during Stop, but it makes no difference. I'm guessing that this affects the output only for the G-Code STOP button, and has nothing to do with eStop sadly. Seems strange that Mach3 could do this and Mach4 cannot as far as I can tell.

Taking Force9 at their word (that charge pump is redundant in ESS designs) I have switched the PMDX-126/107 to non charge pump mode instead, and the eStop now releases correctly.
« Last Edit: April 30, 2021, 10:56:40 AM by jrbloom »