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Messages - freedom2000

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OK it's clear now  ;)


Thanks JP - now working. FWIW I first tried this on my simulation Mach PC - i.e. no PP driver and although the Torch On/Off worked the TorchUP/Down didn't - the LEDs lit but no Z activity. Then I remembered a similar keyboard emulation issue I had a while back with the probe signal. It only actually works with the PP driver loaded. Sure enough the same seems to apply in this case.

thanks again


Ok that's cool !

BTW, what do you mean with "pp driver" ?


Hi JP. I too have been trying to simulate control of Torch Up/Down via keyboard emulation in ports n pins. I get the Torch Up/Down LEDs lighting on the Diagnostics page but no Z movement in the DRO. I've made a call to StartTHC (THCOn() throws a script syntax error) but this makes no difference. What am I missing?
Hi Ian,

I have also emulated the torch on signal with a keyboard key. Then I have loaded a Gcode file at constant height.
When pressing the "torch on" key the cutting starts
when releasing the torch on key the cutting stops
when pressing the torch on + torch Up then the cutting height increases
with the torch down it decreases.

Well quite simple in fact
motion = torch on pressed
motion + torch up or down --> the height climbs or decreases


Hi Matt,

In fact the plugin is not needed. My problem was only due to a missing THC On signal !!!

Now everything is in order and when emulating these signals (THCon, TCH up, THC down) Mach3 takes into account the height correction properly.

I have also progressed a bit.

Here is the schema of the electronics :

The voltage divider has been supressed as my Cut 50L provides a signal from 3V to 7V (when cutting) up to 90V when starting the arc.
The two diods on LM331 inputs are there to limit the voltage between -0.6V to 12.6V that is to the usefullrange of the torch signal.

I have not yet tested this schema excepted the inputs to the LM331.

For the moment I am finishing my CNC  !
More details here (in french) : http://www.usinages.com/ma-fraiseuse-v2-a-vos-critiques-svp-t8144-90.html


For sure I will keep you  informed. As we say in France : "c'est la moindre des choses" !

BTW I am not yet sure how I can handle the negative voltage of the arc with the LM331... I will see !

I have just received the optocoupler today
still waiting for the LM331

And I have found into my plasma two devoted pins where to pick up the arc voltage  :o

I have tried to emulate the Torch Up and torch down with keyboards in Mach3... but I don't see any effect in the Z DRO when running...
Any idea ?



Mach already has all of the logic for dthc built in so there is no need to use anything else, my brain simply compares my value read in (in the process described above) with the value i have typed into dro 1036 i think, but its whatever is in the candcnc screenset for preset volts and moves up if the voltage is too low or down if its too high, the thc controls are there in the brain editor under thc up and thc dwn, and mach does the rest, if all criteria are met, arc ok signal is on and thc is turned on it will adjust the torch position.

Bingo youve got dthc

I have also been looking at how to do this with no pokeys, i think if i was to put a simple analogue to digital converter on my analogue voltage and reading in the pulses across the parrallel port using the spindle speed input or something which will measure frequency, this may also give the advantage of a wider working band, the limitation with my device is that i am taking a perhaps 10v variation and reducing it to perhaps 0.5v variation and then mathematically multiplying it back up, so there is error but in fairness to it i can make a 200mm long cut with one end of the material raised by 50mm and the cut height is pretty constant and when im hundreds in pocket i cant complain.


Fisrt of thank you Matt for this great idea.

I think that I will try to do the suggestion with using the spindle speed input. The pulse signal should be easily generated by a tension to frequency converter such as the so cheap LM331.

Something like this (but only from the left to the optocoupler)

My only doubt compared to your pokeys solution is that with the LM331 I will only have one input which will prevent me to do the averaging that you perform in the brain while using several imputs on your pokeys...

Well I will see and keep you informed


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