MACH3 and MPG Pendant

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ctwo
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MACH3 and MPG Pendant

Post by ctwo »

Hey All,

I was trying to set up my MPG pendant on my Bridgeport CNC and managed to successfully burn out my C22 BoB. It's a simple parallel BoB (not modbus) with just resistors and a couple of octal bus transceiver chips. Actually, just two resistors burned and they were connected to the LPT pins on the PC side, so I'll need to test my parallel port too. The BoB was installed inside the PC to a pin header on the PCI parallel card, and I used a 5V (red) line from the PC power supply, which can probably supply 20 amps :roll: The only thing I can think of that was wrong is that perhaps the parallel port card's internal pin header is not an LPT port, but device manager did show 3 LPT ports and the card only has one external port (and the MB has one).

The pendant is a generic 6-axis pulse generator, model tm1469-100bs-l5 (Handwheel Pulse Generator, Encoder, TM1469-100BS-L5 Wide Number System, Mitsubishi System). Just two knobs:

Off, X, Y, Z, 4, 5, 6
X1, X10, X100
100 detent encoder knob

The pendant pin label attached below.

I think I am realizing this will not be compatible with a simple BoB from CNC4PC because it has a 5V and a 24V pin, and nowhere in this system is 24V. I also do not know what A/, B/, +, -, and COM do (I thought COM would mean common ground but says +5Vdc in the setup guide). Does anyone have an idea?

I was able to see the 4th, 5th, and 6th axis select pin toggle in MACH3's input diagnostic indicators (looks like pins 10, 18 and 19 on the parallel port side, but I do not know which MACH3 indicators correspond to which pins) and pin 6 output led on the pendent would switch on/off with various MACH3 settings, so there was some communication, but many of the other port 1 pin indicators were just stuck on, the ones in second row towards end.
(setup using this guide: https://cnc4pc.com/Tech_Docs/GUIDE_FOR_ ... PLUGIN.htm)

Also, in MACH3 setup, there is a B Port set to pin 3 but I don't know what port B means or what it's used for?
Attachments
cnc-pendent-20200713_082728.jpg
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ctwo
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Re: MACH3 and MPG Pendant

Post by ctwo »

Update:

I pulled out my oscilloscope and using the pinout chart on the setup site linked above, I measured each pin on the pendant and parallel port of the BoB, after bridging pin 1, output#6 to 5V. It all works just as it's supposed to, except I am puzzled that there are pulses on the MPG CH A+ and MPG CH B+ on both ends, but there are no pulses on the MPG CH A- and MPG CH B- on the PC side, and those pins are not connected to the port connector, plus they are not assigned in the software setup. It kind of makes sense that you would just need one set of pulses to determine direction, so it must only use the positive pulses.

Now I'm off to test the PC parallel port. It might be as simple as I picked the wrong LPT port in the setup. Perhaps the internal port is LPT2 and the external is LPT3. I still have no answer for why the two resistors burned. ? They go to pins 10 and 13, which would be driven by the SN74ACT245 transceiver chip, which can only source or sink 20mA and could not burn the resistors without taking out the chip, and the chip works!
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...
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Re: MACH3 and MPG Pendant

Post by ctwo »

Well, now I am more than perplexed. IT WORKS! But not after some fiddling with settings, and all I really did was change the port setting to the second resource range and then back again, so it's set up exactly how I had it originally. After doing that, all of the diagnostic pins would toggle when I shorted the parallel port pins.

Next obstacle is figuring out why MACH3 sometimes listens to the pendent and sometimes not. I've discovered that merely opening the cal dialog and closing it brings the pendant back online. I'm kinda skeptical it will work reliably since the input pins were only halfway responding on the diagnostic screen the first time around, and the LED on the pendent would either fully illuminate or halfway illuminate when in the OFF position.

I don't think I like it as much as I was expecting.

When I change the multiplier knob, it always changes the step to 0.01, 0.1, or 1.0. I want it to be 0.001, 0.01, and 0.1 for the X1, X10, and X100. Maybe there is a file that needs to be changed. Who wants their machine to move an inch when you move dial one thousands?

Second is using either velocity or velocity/step seems to move random amounts. The movement mostly matches how I change the dial in speed and when I stop, but you could not machine using those modes. You couldn't machine using the single or multi step modes either. In single step, it will miss counts if you keep turning without waiting for it to complete the step. Multi step keeps dead track of where the dial had moved, even the pauses as you're looking to find the right detent, but it's too jerky. Maybe I need to slow the feed rate to some actual manual machining speed? I'm gonna go out and try it again.

Whoo Hoo! How many years have I had this machine with the pendent sitting in a box?

BTW, if I could edit my first post, I would let the readers know that they can skip to post #3 (or maybe #5 by tomorrow :lol: ) since the original ramblings seem to have been solved.
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...
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ctwo
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Re: MACH3 and MPG Pendant

Post by ctwo »

Seems that MACH3 has trouble initializing the port. I have to fiddle with the port setting many times and I got it to work only a couple times after rebooting MACH3. Or it could be a faulty parallel port card.

Then I found another setup guide that talks about brains so will try that tomorrow. https://cnc4pc.com/Tech_Docs/guide_for_ ... r_LPT2.htm

Oh, and I found the X1, X10, and X100 step size settings.
Last edited by ctwo on Tue Jul 14, 2020 1:56 am, edited 1 time in total.
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...
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Re: MACH3 and MPG Pendant

Post by Harold_V »

So you know your posts are being read, I'm responding. If only I understood what you're talking about! :oops:

H
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Re: MACH3 and MPG Pendant

Post by rrnut-2 »

And my experience is with Centroid.

Jim B
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Re: MACH3 and MPG Pendant

Post by NP317 »

I'm with Harold!
What is an MPG Pendant?
'Sounds like a necklace that provides mileage...
Foreign language to me for sure.
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ctwo
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Re: MACH3 and MPG Pendant

Post by ctwo »

I could not get it to work today. Brains don't seem to matter. I tried a parallel port monitor and at least it would toggle the "output" pins that seem stuck in MACH3. It does not monitor pins 2-9 as input pins, however, and I could not find one. MACH only indicates activity on pins 10-13, usually with 2-9 stuck high, but now they are stuck low, probably because that is how I set them in the parallel port monitor.

Maybe I will buy a modbus BoB, or I discovered that there is a modbus software library for the popular Arduino microcontroller, so maybe I will make my own, or try another PCI Parallel port adapter.
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
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ctwo
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Re: MACH3 and MPG Pendant

Post by ctwo »

NP317 wrote: Tue Jul 14, 2020 10:15 am I'm with Harold!
What is an MPG Pendant?
'Sounds like a necklace that provides mileage...
Foreign language to me for sure.
RussN
MPG is a manual pulse generator. I don't know why they called it a pendant, but probably because it's on a cord and usually hangs around the machine somewhere. It's basically a manual hand controller for the CNC motors.

It's like a steering wheel for your computer car racing game, as opposed to using the keyboard.
Standards are so important that everyone must have their own...
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Disclaimer: I'm just a guy with a few machines...
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Re: MACH3 and MPG Pendant

Post by ctwo »

So reading more I see people had been having problems with some parallel port cards. On the Mach forum there was a suggestion to get a netmos chipset so I bought a used pull off ebay. We'll see. Maybe next week.
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Re: MACH3 and MPG Pendant

Post by NP317 »

Thanks for explanation.
Always something to learn.
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Re: MACH3 and MPG Pendant

Post by Steggy »

ctwo wrote: Mon Jul 13, 2020 10:41 amI was trying to set up my MPG pendant on my Bridgeport CNC and managed to successfully burn out my C22 BoB. It's a simple parallel BoB (not modbus) with just resistors and a couple of octal bus transceiver chips. Actually, just two resistors burned and they were connected to the LPT pins on the PC side, so I'll need to test my parallel port too.
The type of failure you are describing is typical of when contention occurs on a parallel port. The port's transceiver is usually not able to tolerate contention for more than a few seconds, mainly because of the use of 74AC logic, which has strong drive. Since 74AC logic can swing from rail to rail, a lot of magic smoke can get out in short order, especially considering the copious amount of current that can be emitted by a typical PC power supply.
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