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Manual

THCUD(9)

HAL Component

THCUD(9)

NAME

thcud - Torch Height Control Up/Down Input

SYNOPSIS

loadrt thcud

DESCRIPTION

Torch Height Control This THC takes either an up or a down input from a THC

If enabled and torch is on and X + Y velocity is within tolerance of set speed allow the THC to offset the Z axis as needed to maintain voltage.

If enabled and torch is off and the Z axis is moving up remove any correction at a rate not to exceed the rate of movement of the Z axis.

If enabled and torch is off and there is no correction pass the Z position and feed back untouched.

If not enabled pass the Z position and feed back untouched.

Typical Physical Connections using a Parallel Port
Parallel Pin 12 <= THC controller Plasma Up
Parallel Pin 13 <= THC controller Plasma Down
Parallel Pin 15 <= Plasma Torch Arc Ok Signal
Parallel Pin 16 => Plasma Torch Start Arc Contacts

HAL Plasma Connections
net torch-up thcud.torch-up <= parport.0.pin-12-in
net torch-down thcud.torch-down <= parport.0.pin-13-in
net torch-on spindle.0.on => parport.0.pin-16-out (start the arc)
net arc-ok thcud.arc-ok <= motion.digital-in-00 <= parport.0.pin-15-in (arc ok signal)

HAL Motion Connections
net requested-vel thcud.requested-vel <= motion.requested-vel
net current-vel thcud.current-vel <= motion.current-vel

PyVCP Connections In the XML file you need something like:

<pyvcp>
<checkbutton>
<text>"THC Enable"</text>
<halpin>"thc-enable"</halpin>
</checkbutton>
</pyvcp>

Connect the PyVCP pins in the postgui.hal file like this:

net thc-enable thcud.enable <= pyvcp.thc-enable

FUNCTIONS

thcud (requires a floating-point thread)

PINS

thcud.torch-up bit in: Connect to an input pin
thcud.torch-down bit in: Connect to input pin
thcud.current-vel float in: Connect to motion.current-vel
thcud.requested-vel float in: Connect to motion.requested-vel
thcud.torch-on bit in: Connect to spindle.N.on
thcud.arc-ok bit in: Arc Ok from Plasma Torch
thcud.enable bit in: Enable the THC, if not enabled Z position is passed through
thcud.z-pos-in float in: Z Motor Position Command in from axis.n.motor-pos-cmd
thcud.z-pos-out float out: Z Motor Position Command Out
thcud.z-fb-out float out: Z Position Feedback to Axis
thcud.cur-offset float out: The Current Offset
thcud.vel-status bit out: When the THC thinks we are at requested speed
thcud.removing-offset bit out: Pin for testing
thcud.correction-vel float in: The Velocity to move Z to correct

PARAMETERS

thcud.velocity-tol float rw: The deviation percent from planned velocity

AUTHOR

John Thornton

LICENSE

GPLv2 or greater

2025-12-31

LinuxCNC Documentation