Hoistway Signal Circuit (HW)
1 Overview
The Hoistway Signal Circuit (HW) consists of leveling switches and terminal switches that provide critical position and safety information to the elevator control system.
1.1 Leveling Switches (PAD Sensors)
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Function: Detect cAr position for floor leveling, door operation zones, and re-leveling areas.
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Common Signal Combinations:
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DZD/DZU: Main door zone detection (car within ±50mm of floor level).
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RLD/RLU: Re-leveling zone (narrower than DZD/DZU).
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FDZ/RDZ: Front/rear door zone signals (for dual-door systems).
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Key Rule:
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If either RLD/RLU is active, DZD/DZU must also be active. Violation triggers door zone safety protection (see SF Circuit).
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1.2 Terminal Switches
| Type | Function | Safety Level |
|---|---|---|
| Deceleration | Limits car speed near terminals; aids position correction. | Control signal (soft stop). |
| Limit | Prevents overtravel at terminals (e.g., USL/DSL). | Safety circuit (hard stop). |
| Final Limit | Last-resort mechanical stop (e.g., UFL/DFL). | Cuts #5/#LB power. |
Note: Machine-room-less (MRL) elevators may repurpose upper terminal switches as manual operation limits.
2 General Troubleshooting Steps
2.1 Leveling Switch Faults
Symptoms:
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Poor leveling (±15mm error).
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Frequent re-leveling or "AST" (Abnormal Stop) faults.
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Incorrect floor registration.
Diagnostic Steps:
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PAD Sensor Check:
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Verify gap between PAD and magnetic vane (5–10mm).
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Test sensor output with multimeter (DC 12–24V).
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Signal Validation:
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Use P1 board's debug mode to display PAD signal combinations as the car passes floors.
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Example: Code "1D" = DZD active; "2D" = DZU active. Mismatches indicate faulty sensors.
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Wiring Inspection:
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Check for broken/shielded cables near motors or high-voltage lines.
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2.2 Terminal Switch Faults
Symptoms:
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Emergency stops near terminals.
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Incorrect terminal deceleration.
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Inability to register terminal floors ("write layer" failure).
Diagnostic Steps:
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Contact-Type Switches:
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Adjust actuator dog length to ensure simultaneous triggering of adjacent switches.
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Non-Contact (TSD-PAD) Switches:
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Validate magnet plate sequence and timing (use oscilloscope for signal analysis).
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Signal Tracing:
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Measure voltage at W1/R1 board terminals (e.g., USL = 24V when triggered).
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3 Common Faults & Solutions
3.1 Inability to Register Floor Height
| Cause | Solution |
|---|---|
| Faulty Terminal Switch | - For TSD-PAD: Verify magnet plate insertion depth (≥20mm). - For contact switches: Adjust USR/DSR actuator position. |
| PAD Signal Error | Confirm DZD/DZU/RLD/RLU signals reach the control board; check PAD alignment. |
| Board Fault | Replace P1/R1 board or update software. |
3.2 Automatic Terminal Re-Leveling
| Cause | Solution |
|---|---|
| TSD Misalignment | Re-measure TSD installation per drawings (tolerance: ±3mm). |
| Rope Slippage | Inspect traction sheave groove wear; replace ropes if slippage >5%. |
3.3 Emergency Stop at Terminals
| Cause | Solution |
|---|---|
| Incorrect TSD Sequence | Validate magnet plate coding (e.g., U1→U2→U3). |
| Actuator Dog Fault | Adjust length to ensure overlap with limit switches. |
4. Diagrams
Figure 1: PAD Signal Timing
Figure 2: Terminal Switch Layout
Document Notes:
This guide aligns with Mitsubishi elevator standards. For MRL systems, prioritize TSD-PAD magnet plate sequencing checks.
© Elevator Maintenance Technical Documentation
