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G31 Doesn't work properly
« on: January 22, 2014, 01:38:01 AM »
Okay, here's my setup. I have a passive probe from tormach wired into my mach3 (non tormach) machine. One wire to pin 15 as an input and the other to ground. I also have a 220 ohm resistor between the input and 5v (like the second wiring drawing on this page : http://www.cnc4pc.com/Store/osc/product_info.php?products_id=323)

I enabled the pin in Mach3 for probe and leave the active low unchecked. After this I can go into the diagnostics page and see the probe light come on and off as I press on the stylus. However, if I run any G31 command in the MDI, nothing at all happens. No movement and no DRO reaction.

Next, if I go back to ports and pins and enable Active low for the probe, then in the diagnostics screen the led behaves opposite of what it should (as you would expect). But, if I press and hold on the stylus of my probe and run G31, it starts probing until I let go.

So what gives? It works in reverse (which is incorrect), but now how it's supposed to. What am I missing? Do I need a capacitor or something on the probe wiring? I have had the denounce up to 4000 with no noticeable change. Any ideas??

Offline stirling

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Re: G31 Doesn't work properly
« Reply #1 on: January 22, 2014, 03:53:54 AM »
sounds like noise so the usual procedures - check connections, screening, capacitors, debounce.

One thing you could try first though is to switch it to active low. Connect one probe wire to 5V and the other to your input and change the resistor to a pull-down i.e. between pin and ground. I'd also replace the resistor with a higher value. somewhere between 1K and 10K. That 220 is very low for a pullup and is used with that other probe to allow sufficient current to light the LED.
Re: G31 Doesn't work properly
« Reply #2 on: January 22, 2014, 04:20:16 AM »
Yup, swapping to 5V / Active Low did it. Good call about the lower resistor/led current. Must be a noise issue. I was worried about having 5V in the probe incase it shorted to the machine but it seems to be relatively isolated and also anodized which seems to prevent any current transfer. Thanks for the tips. Now into figuring out how to calibrate the 3 adjusters on this thing.
Re: G31 Doesn't work properly
« Reply #3 on: January 22, 2014, 04:22:22 AM »
Also, I just let the breakout board handle the pull-up resistor since it is already doing this for my limits. Maybe that was part of my problem, I had an external pull down resistor but the board was probably then pulling it back up.