LS PLC XGQ-TR4A Programmable Logic Controller XGT Series Output Module XGQ-TR4A,EXP XGQ-TR4A

LS Electric XGQ-TR4A | XGK 32-Point NPN Sink Transistor Output Module — DC 12/24V / 0.1A per Point / 2A Common / Photocoupler / ≤1ms

NPN Sink — What It Means for Field Wiring

The XGQ-TR4A is the NPN (sink) variant of the XGK 32-point transistor output module. Its PNP (source) counterpart is the XGQ-TR4B. The distinction is fundamental to field wiring:

NPN (sink) — XGQ-TR4A: Each output transistor provides the return path to COM (0V). The field supply's positive terminal connects to the load; the transistor connects the load's other terminal to COM when commanded ON. Current flows from supply → load → transistor → COM.

PNP (source) — XGQ-TR4B: Each transistor provides the positive supply. COM carries 24V; the transistor connects 24V to the load when commanded ON. Current flows from COM → transistor → load → 0V.

If field devices have one terminal connected to the 24V positive bus and require a switched return to 0V, NPN is correct. If devices have 0V connected and require a switched 24V supply, PNP is correct. Specifying the wrong type produces wiring where outputs have no effect regardless of programme state.

Key Specifications

2A Common Limit — The Practical Constraint

Each point can sink 0.1A; the common terminal is shared with a 2A maximum. With 32 points at full 0.1A each, simultaneous current would reach 3.2A — exceeding the limit. In practice:

• At 0.1A per point: maximum 20 outputs simultaneously ON (20 × 0.1A = 2.0A)
• At 0.05A per point (50mA solenoid coil): all 32 outputs = 1.6A — within limit
• At 0.06A per point: all 32 = 1.92A — within limit

Most real-world loads — 24VDC solenoid coils, signal relay coils, LED indicators — draw 30–60mA. For these, 32 simultaneous active outputs stay well within the 2A common limit. The constraint matters only in dense applications driving many high-current loads simultaneously.

Application Scenarios

Pneumatic valve panels: 32 valve pilots at 24VDC, 50–80mA each. Total current at 70mA × 32 = 2.24A approaches but depends on simultaneous activation — in cyclic applications where not all valves fire simultaneously, well within the 2A limit.

Signal relay driving: XGQ-TR4A outputs driving 24VDC relay coil inputs (30–50mA each). All 32 simultaneously = 0.96–1.6A — well within common limit.

LED indicator panels: 32 status indicators at ≤20mA each. All 32 active = 0.64A — no constraint applies.

FAQ

Q1: Can NPN outputs drive inductive loads (solenoid coils) directly?

Yes, within the 0.1A per-point limit. Inductive loads generate a back-EMF spike when switched off — suppress with a freewheeling diode across the coil (cathode to positive supply, anode to switched terminal). Without suppression, back-EMF degrades transistor life and can cause spurious switching on adjacent wiring. Verify whether the specific solenoid coil already includes internal suppression.

Q2: What does ≤1ms response time mean for real applications?

The 1ms transistor delay — from PLC output command to terminal state change — is negligible for solenoid valve, conveyor, and indicator applications where the controlled device responds in 10–100ms. For microsecond-precision timing (stepper motor pulse generation), a dedicated high-speed pulse output module is required; a standard transistor module is not appropriate.

Q3: Is the XGQ-TR4A compatible with the XGB compact PLC?

No. The XGQ-TR4A is an I/O module for the XGK modular PLC bus. The XGB uses a different expansion bus format with its own specific expansion modules. For XGB systems, the appropriate XGB-series transistor output module must be specified.

Q4: How is a used XGQ-TR4A verified before installation?

Mount in an XGK base, power the system, command each of the 32 channels ON and OFF individually via a test programme or diagnostic function. Verify at each output terminal: ≤0.2V when ON; floats to supply voltage when OFF. Any channel remaining near 0V when commanded OFF (stuck closed) or failing to pull below 0.2V when ON (stuck open) has a failed transistor. Confirm LED behaviour matches expected ON/OFF states throughout.

Q5: Where is the XGQ-TR4A sourced after discontinuation?

Through the LS Electric XGK aftermarket — industrial automation spare parts dealers and tested surplus suppliers. Request tested units with individual channel verification. Confirm XGQ-TR4A (NPN, 32-point) vs XGQ-TR4B (PNP, 32-point) before ordering — the NPN/PNP distinction is critical for wiring compatibility.