What you'll learn
Connect a Type 4 light curtain to a safety relay using two independent OSSD channels, then use a safety output contact to interrupt a contactor coil. Functional earth drains interference; it is not the 0 V operating return.
Lab time: ~22 minutes.
Lesson briefing
Safety Light Curtain with Dual OSSD
Connect a Type 4 light curtain to a safety relay using two independent OSSD channels, then use a safety output contact to interrupt a contactor coil. Functional earth drains interference; it is not the 0 V operating return.
Why it is wired this way
OSSD1 and OSSD2 are pulsed semiconductor safety outputs. A safety relay checks both channels for agreement and detects shorts to supply, 0 V or each other. Never parallel the two outputs into one ordinary PLC input.
Commissioning standard
Before energising, prove protective earth and continuity, verify the drawing terminal-by-terminal, then energise through the protective device and measure the expected supply, signal and return values. Never use this training panel as a substitute for the machine manufacturer’s instructions, risk assessment, isolation procedure or applicable electrical standard.
Hints
Give the light curtain its own +24 V and 0 V supply plus FE bond.
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This lesson uses 7 placed components on the lab canvas. Components are vendor-neutral (no proprietary trademarks); the wiring rules apply to any equivalent industrial part.
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