The QCA is an external safety relay controller designed to work with DADISICK QC, QE, and QT series safety light curtains. When the connected light curtain detects an object entering the protected zone, the QCA instantaneously reverses its output states — the normally open contact opens and the normally closed contact closes — providing a reliable stop signal to the machine control circuit. This hardwired relay architecture ensures fail-safe operation independent of software-based safety logic.

How is the QCA integrated into a machine safety circuit?

The QCA is installed in the equipment control cabinet and wired between the safety light curtain pair and the machine's emergency stop or control circuit. It receives the OSSD (Output Signal Switching Device) signals from the light curtain transmitter-receiver pair and drives its internal relays accordingly. The standard configuration provides one normally open and one normally closed contact set rated at 5 A for AC250 V or DC30 V resistive loads, sufficient for directly interrupting contactor coils or safety relay inputs. For applications requiring redundant outputs, a special-order variant with two NO and two NC contact sets is available.

What operational modes does the QCA support?

The QCA offers two configurable operating modes to suit different machine safety workflows:

• Reset Mode: Manual reset requires an operator to press an external reset button after each light curtain interruption before the outputs re-energize, suitable for full-body access guarding. Automatic reset restores outputs as soon as the light curtain is clear, used where the protected zone cannot be entered by personnel.
• Channel Mode: Single channel mode uses one OSSD input path, while dual channel mode cross-checks both OSSD signals for agreement, detecting short circuits and wiring faults in the light curtain connection.

What safety performance does the QCA achieve?

The QCA is certified to SIL 3 (per IEC 61508), PL e (per ISO 13849), and Category 4 (per ISO 13849) safety standards, the highest classification achievable for a safety-related control system using a single-channel architecture with diagnostics. The combined response time of the QCA and connected light curtain is ≤20 ms, meeting the requirements for high-risk applications where stopping time directly determines the minimum safety distance. Dielectric strength is rated at AC1500 V for 60 seconds, and the internal relays are rated for over one million electrical operations.