Bench testing Mesa THCAD

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rodw
Topic Author
Away
Platinum Member

08 Jan 2017 01:21 #85441 by rodw

Bench testing Mesa THCAD was created by rodw

I've been setting up my THC using Mesa 7i767 and a THCAD-10. I have not attached a plasma yet but have been doing some tests.

I've got most of the THC signals working eg.
arc-ok - using a switch to +24v
torch-on - Turns on a temporary light attached to the torch on relay when M3 is sent
enable - I attached this to an unused input pin-not and its working
encoder-vel - Counts away merrilly
current-vel - shows speed on Z axis in metres per second that agrees with a gcode S command in mm/min

But I figured once I got this far I should be able to see the volts output.
I stole some 5v poser from a stepper input and put -5v to THCAD IN- and then ran the +5v through a 100k pot to THCAD +IN
This is giving me a voltage range of 2.5v to 5.0V on the THCAD 10 volt range.

I'm not seeing anything in HAL Configuration. DO I need to attach the THCAD plasma input side to ground?

Here is my HAL stuff

# --- TOUCH OFF ---
net torch-probe motion.probe-input <= hm2_7i76e.0.7i76.0.0.input-09-not

# --- THC - TORCH HEIGHT CONTROLLER ---
# thc calibration data 0v = 122.9 kHz (122900), 10v = 925.7 kHz (925700)
# freq(x) = 122900 + 80280 * V
# so at 10V, 925700 = 122900 + (80280 * 10)
# 1/80280 = 0.000012456

setp thc.vel-scale 0.000012456
setp thc.scale-offset 122900
setp thc.velocity-tol 1.0
setp thc.voltage-tol  1.0
#This might need to be increased
setp thc.correction-vel 0.00001
setp hm2_7i76e.0.encoder.00.counter-mode 1

net thc-encoder-vel hm2_7i76e.0.encoder.00.velocity => thc.encoder-vel
net thc-current-vel thc.current-vel      <= motion.current-vel
net thc-requested-vel thc.requested-vel    <= motion.requested-vel
net spindle-on => thc.torch-on
# starts the motion when the plasma arc has transfered to the work
net start-motion-input thc.arc-ok <= motion.digital-in-00  <= hm2_7i76e.0.7i76.0.0.input-10

#enable THC just for TESTING 
net thc-enable thc.enable <= hm2_7i76e.0.7i76.0.0.input-31-not 

#unused THC inputs
#net thc.volts-requested  
#net thc.vel-tol

#thc.z-pos-in

# THC outputs below
#net thc.z-pos-out
#net thc.z-fb-out
#net thc.volts
#net thc.vel-status
#net thc.offset-value

# --- ARC OK OUTPUT (to LED) ---

net start-motion-input => hm2_7i76e.0.7i76.0.0.output-03

Any help would be appreciated.

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rodw
Topic Author
Away
Platinum Member

08 Jan 2017 03:38 - 08 Jan 2017 03:39 #85447 by rodw

Replied by rodw on topic Bench testing Mesa THCAD

I worked this out. The wiring was correct. I had the THCAD frequency set on the board to be 1/32. My scale and offset config needed to be:

# --- THC - TORCH HEIGHT CONTROLLER ---
# thc calibration data 0v = 122.9 kHz (122900), 10v = 925.7 kHz (925700)
# so at 10V: 925700 = 122900 + (80280 * 10)
# but we are using 1/32 divider on THC board
# 1/32: input 0v = 3840.625, 10v = 28928.125
# 1/32 at 10v:  28928.125 = 3840.625 + (2508.75 * 10) 
# 1/32 scale = 1/2508.75 = 0.000398605

setp thc.vel-scale 0.000398605
setp thc.scale-offset 3840.625

The voltage output in HAL now seems to be remarkably accurate!

Last edit: 08 Jan 2017 03:39 by rodw.

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