How to connect an amplifier to a light curtain

A light curtain amplifier is connected to the receiver of the light curtain to process safety signals, enabling muting, diagnostics, and integration with safety relays or PLCs.

Overview

A safety light curtain consists of a transmitter and a receiver. The transmitter emits infrared beams, and the receiver detects interruptions to create a safety barrier. When an object interrupts the beams, the receiver sends a signal to stop hazardous motion or trigger a safety function.

To enhance functionality, a light curtain amplifier (or muting amplifier) is used to process these signals, manage muting, and provide diagnostic information.

Wiring and Signal Types

Power Supply: The receiver requires a 24 V DC power supply, while the transmitter typically only needs power. Output Signals: Light curtain outputs can be NPN (sinking) or PNP (sourcing). The amplifier must match the output type of the light curtain and the input type of the downstream safety device, such as a PLC or safety relay.

Normally Open (NO) vs Normally Closed (NC): NC outputs are preferred in safety applications because they can indicate a fault if wiring is disconnected, enhancing reliability. Typical wiring includes connecting the receiver's output to the amplifier input, which then interfaces with a safety relay or PLC. The amplifier may also handle muting signals from sensors to allow material to pass without stopping the machine.

Muting and Safety Integration

Muting: Some amplifiers, like the UE403 used with SICK M4000 light curtains, allow two-sensor L-type muting, enabling objects to pass through the curtain without stopping machinery. Safety Relays: Amplifiers often connect to a configurable safety relay (e.g., Guardmaster 440C-CR30) to implement emergency stops and safety functions. Diagnostics: Modern amplifiers provide status and diagnostic outputs, simplifying commissioning and reducing downtime.

Practical Tips

Ensure the amplifier and light curtain are compatible in terms of voltage, output type, and safety category. Follow manufacturer wiring diagrams carefully to maintain Performance Level (PLd or higher) compliance. Use proper mounting and alignment to avoid false triggers or missed detections.

Test the system after installation to verify that muting, emergency stop, and normal safety functions operate correctly. By connecting the amplifier correctly, the light curtain can provide reliable safety monitoring, muting functionality, and integration with industrial control systems, ensuring both safety and operational efficiency.