| OHMIC(9) | HAL Component | OHMIC(9) |
NAME¶
ohmic - LinuxCNC HAL component that uses a Mesa THCAD for ohmic sensing
SYNOPSIS¶
loadrt ohmic [count=N|names=name1[,name2...]]
DESCRIPTION¶
Mesa THCAD Card component to scale input and outputs from the Mesa
THCAD2, THCAD5, THCAD10, and THCAD300 cards.
Allows user configurable voltage thresholds for ohmic sensing.
Output pins are provided for:
ohmic-volts -the voltage sensed on ohmic sensing.
thcad-volts -the actual voltage measured by the THCAD.
ohmic-on -true if ohmic-volts >= ohmic-threshold, false if ohmic-volts
<= ohmic-low.
A THCAD-5 would often be used for ohmic sensing in conjunction
with a 24 Volt isolated power supply and a 390 kΩ series resistor
resulting in a voltage divider of 4.9.
This would result in a full scale reading of 24.5 Volts which is above the
power supply output voltage.
The circuit will remain protected by the THCAD's ability to tolerate a 500
Volt over-voltage indefinitely.
It is optional that power to the ohmic sensing circuit be disconnected unless
probing is in progress.
FUNCTIONS¶
PINS¶
- ohmic.N.is-probing bit in
- True if probing
- ohmic.N.ohmic-low float in (default: 21)
- The threshold volts below which ohmic sensing is set to be false
- ohmic.N.ohmic-threshold float in (default: 22)
- The threshold volts above which ohmic sensing is set to be true
- ohmic.N.thcad-0-volt-freq float in
- 0 volt calibration data for THCAD card in Hz
- ohmic.N.thcad-divide float in (default: 32)
- THCAD divider set by links on THCAD board (1, 32, 64, or 128)
- ohmic.N.thcad-fullscale float in (default: 5)
- THCAD full scale in Volt (5, 10, or 300 Volt)
- ohmic.N.thcad-max-volt-freq float in
- Full scale calibration data for THCAD Card in Hz
- ohmic.N.velocity-in float in
- The velocity returned from the THCAD and read by the Mesa encoder input
- ohmic.N.volt-divider float in (default: 4.9)
- The divide ratio
- ohmic.N.ohmic-on bit out
- True if ohmic circuit is closed (material is sensed)
- ohmic.N.ohmic-volts float out
- Calculated ohmic voltage
EXAMPLES¶
The below HAL example assumes a THCAD5 card using a 1/32 frequency
setting and a voltage divider internal to the plasma cutter with range
extended to 24.5 volts by a series 390K external resistor as per the manual.
Additional information and wiring diagram is contained in the Plasma Primer
in the LinuxCNC documentation.
Example Calibration Data: 0V = 122.9 kHz, 10V = 925.7 kHz should be entered as
122900 and 925700.
loadrt ohmic names=ohmicsense
addf ohmicsense servo-thread
setp ohmicsense.thcad-0-volt-freq 122900
setp ohmicsense.thcad-max-volt-freq 925700
setp ohmicsense.thcad-divide 32
setp ohmicsense.thcad-fullscale 5
setp ohmicsense.volt-divider 4.9
setp ohmicsense.threshold 22
setp ohmicsense.ohmic-low 21
net ohmic-vel ohmicsense.velocity-in <= hm2_7i76e.0.encoder.00.velocity
net ohmic-enable ohmicsense.is_probing <= plasmac.ohmic-enable
net ohmic-true ohmicsense.ohmic-on => plasmac.ohmic-probe
AUTHOR¶
Rod Webster
LICENSE¶
GPL
| 2024-07-13 | LinuxCNC Documentation |