The operator sees a missing location, stale gas or dust data, or no local red-light and vibration alarm when the measured signal rises. Do not start by replacing the radio module. Split the system into four paths: sensor acquisition, threshold logic, wireless transfer, and the wired bus to the command center.
Reject the usual quick fixes
Power cycling may restore a stalled node, but it erases the symptom without locating the fault. Raising alarm thresholds hides a bad analog channel. Increasing radio coverage cannot repair a failed sensor amplifier or a broken wired bus.
| Quick fix | Why it fails | Reading to take first |
|---|---|---|
Replace the MC13192 module |
The sensor value may never reach the transmitter. | Compare the sensor output, amplifier output, and controller value. |
| Move a receiver | Changing a fixed monitoring point can invalidate the location map. | Check whether other worker transmitters reach the same receiver. |
| Raise the reference value | A calibration or scaling fault remains and the alarm becomes less protective. | Apply a known sensor input and record every state transition. |
| Clear the command-center alarm | Acknowledge and data restoration are separate functions. | Check the packet at the receiver and again on the wired bus. |
Get it running, then fix it properly: use a known-good portable unit or receiver only as a controlled substitution, and return the fixed-node layout and alarm references to their documented values.
Check the sensor path at the worker unit
The portable unit routes sensor outputs through an AD8051 operational amplifier to an MC68HC908LJ12 microcontroller. The controller compares the acquired value with a reference, drives the indicators and vibrator, sends digital data through its I/O to the radio module, and stores digital records in EEPROM.
- Measure the sensor output while applying a known normal input. If it does not respond, troubleshoot the sensor, its supply, and its wiring before the controller.
- Measure the input and output of the
AD8051. A changing input with a fixed or saturated output points to the amplifier stage, its supply, or an out-of-range signal. - Read the digital value used by the
MC68HC908LJ12. If the amplifier output changes but the stored value does not, inspect the conversion path, channel selection, scaling, and firmware. - Compare the live value with a value retrieved from EEPROM. If live acquisition works but records are absent or implausible, isolate the storage function from the radio problem.
The description identifies an internal digital-to-analog converter, but this measurement path requires analog-to-digital acquisition. Resolve that point from the schematic, firmware, and controller datasheet before probing converter pins or rewriting conversion code.
Prove each alarm boundary
The intended states are green for normal, yellow near the reference, and flashing red with vibration for danger. One comparison value cannot define a stable yellow band and a separate red boundary without additional tolerance or threshold logic. Read the implemented limits from the firmware; no numerical gas or dust limits are specified here.
| Applied value | Expected local response | Next decision |
|---|---|---|
| Below the normal boundary | Green indicator | If wrong, check scaling, comparison direction, and output mapping. |
| Inside the critical band | Yellow indicator | If the state chatters, inspect noise, calibration, and hysteresis logic. |
| Above the danger boundary | Flashing red indicator and repeated vibration | If the digital state changes but the outputs do not, inspect the LED and vibrator drivers. |
Test the transitions in both directions. A unit that enters danger correctly but remains there after the input falls may have deliberate latching logic or a defective reset path; determine which from the firmware and operating procedure. Stop the live-input test if it requires exposing personnel to gas or dust. Use the approved calibration method for the installed sensor.
Trace the wireless and wired links separately
The portable controller passes data through its I/O to the MC13192 radio transmitter. Fixed underground radio receivers then forward the information by a wired bus to the surface command center. Treat those as two independent communication tests.
- Confirm that the controller produces a new digital message when the sensor value or alarm state changes. No message means the fault is upstream of the radio link.
- Check whether the assigned underground receiver detects the portable unit. If every portable unit is missing at one receiver, inspect that receiver, its power, antenna path, and local environment. If only one portable unit is missing at several receivers, return to that portable unit.
- Observe the receiver's wired-bus output. Reception without bus activity isolates the fault to the receiver interface or its configuration.
- Check for the same update at the command center. Bus activity at the receiver but no update at the host calls for wiring, bus-interface, addressing, message-integrity, or host-configuration checks.
The bus type, electrical levels, addressing method, and update timing are not specified. Read them from the installed drawings and interface documentation; measure against those limits rather than applying values from another bus family.
Validate the location result and stored record
The command center associates each transmitter number with a worker and uses the arranged monitoring points to display position and measured parameters. This architecture establishes a location only when transmitter identity, fixed receiver placement, and the command-center map agree.
- Place a known transmitter at a documented monitoring point and record its identifier.
- Confirm that the expected fixed receiver or monitoring point reports it.
- Confirm that the command-center graphic shows the same worker identifier at the same mapped position.
- Move the test unit to a second documented point and repeat. A position that never changes indicates a mapping or update problem, not necessarily a failed radio.
- Create a controlled alarm input and compare the local state, received digital value, graphical alarm, audible alarm, and EEPROM record.
The documentation is ambiguous about whether the grid contains fixed receivers or transmitters. Mark the actual fixed devices on the mine drawing before changing the map. Do not infer distance accuracy, ranging, or triangulation unless the installed software and hardware explicitly provide those functions.
Restore production and verify the complete chain
- Repair the first failed stage found in the sequence: sensor,
AD8051amplifier, acquisition logic, local outputs,MC13192link, receiver interface, wired bus, or command-center mapping. - Restore the documented reference values and transmitter-to-worker assignments. Do not leave temporary thresholds or borrowed identifiers in service.
- Apply one normal, one critical-band, and one danger input with approved test equipment.
- At each input, record the controller value, local indication, vibration state, received value, command-center display, and stored EEPROM entry.
- Repeat the radio test from each required monitoring point. Confirm that a message from one worker cannot appear under another worker's identifier.
- Remove the test stimulus and confirm return to the intended normal or acknowledged state.
Production is restored only when the local alarm and remote alarm respond to the same controlled input, the displayed position matches the test point, and the stored record contains the corresponding digital data.
FAQ
Why does the worker unit transmit data but show no local alarm?
The acquisition and radio paths may be healthy while the threshold mapping, LED driver, or vibrator driver has failed. Apply a controlled value above the configured danger boundary and compare the controller state with the red indicator and vibration outputs.
Why does the command center show data but the wrong worker location?
Check the transmitter number, worker assignment, fixed monitoring-point placement, and graphical map as one chain. Test the same known transmitter at two documented points before moving any fixed radio equipment.
Why does an alarm appear locally but not at the command center?
Trace the updated message from the controller I/O through the MC13192, underground receiver, wired-bus output, and host display. Stop here if approved test inputs cannot produce repeatable readings, the converter path cannot be identified from the drawings, or communication limits are unavailable. Isolate the affected equipment and escalate to the equipment manufacturer's official support channel with the measured values, identifiers, wiring documents, and EEPROM records.