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General Mach Discussion / Another THC Hickup I have noticed...Axis acceleration

« on: February 20, 2010, 04:11:24 PM »

It appears to me so far that the THC UP / THC DOWN inputs trigger the z axis to move up and down at her THC RATE, without acceleration.... if I put the THC RATE anywhere close the the max Z axis rate the motor stalls. Is there a way to correct this??? (If I emulate the THC inputs you can tell there is no acceleration.)



On a positive note I do have a working THC circuit for my Powermax 45, It just needs some dialing in on resistor values and i need to stop both outputs being able yo go  high at the same time. Might be a noise thing.

It is one OP-AMP for input impedance and signal inversion, a quad comparator , quad and-gate, and transistor output... resistors and a tun of jumpers all over my breadboard....LOL.

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General Mach Discussion / Interesting driver problem... THC doesnt respond to click.

« on: February 18, 2010, 11:35:51 PM »

Hi all, Im in the process of building a cnc plasma table, and having played a little with a little cnc mill and mach I had noticed that there is a plasma version
When looking into the plasma screen set I noticed there ar some THC commands on it. and figured out to use the inputs (emulated on my laptop) to drive the Z-axis.
After a liitle bit of design work and troubleshooting/re-design, I have the start of my THC circuit. So off to the shed I go , but I cant for the life of me get this thing to go...
the main problem is I wanted to use the THC enable output (#5 on the config screen) to enable / disable my circuit output into Mach3s torch up/down command inputs...
When I click the button, the led and output wont come on... It took some time before I figured out - get this - If I install Mach3 WITHOUT the parallel port driver, the button works... led comes on and off. If I reinstall mach3 WITH the driver.... nothing ?? Am I missing something
I have verified this behavior on 3 different PCs with all the versions available for download.... including R3.042.037

I suppose I can find a way around this... edit my own screen... write a brain... but I just thought It's weird and would like to see it work, because If I can get it working I will post my results as There seems to be lots of questions on a DIY THC but few solutions ... so far I have used a quad comparator , an and gate and a bunch of resistors... might be able to lose the and gate but we will see....