How to Diagnose a Light Curtain Issue Caused by Power Supplies

Diagnosing a Power Supply Problem Affecting Safety Light Curtains on a Delta Robot

We were consulted to troubleshoot a Delta robot that only worked when the safety light curtain’s beam(s) were broken. This is the opposite of how a safety light curtain operates. The problem traced all the way back to the power supplies. Learn the reasons why safety and motion control systems need separate power supplies. Also, discover diagnostic tips our engineers uncovered along the way.

A customer’s Delta robot on a newly installed packaging machine was not operating correctly. Omron was called in to troubleshoot the problem after the installer and machine builder could not find the cause. The Delta robot is protected with an Omron F3SJ-B Safety Light Curtain system connected to a G9SP Programmable Safety Controller and two S8VK-G Power Supplies.
“It’s usually a simple task to connect the F3SJ-B light curtains so we didn’t think this would take very long to fix. After all, it is just a few 24 V and 0 V connections, grey and pink wires from the emitter and receiver being tied together, and some basic programming,” says Mano Kanagaratnam, Omron Senior Technical Support Specialist. “The fact that you are reading this means we were wrong!”
Tina Hull, Omron’s safety expert, reminded us why we need to use separate power supplies for safety and motion. “Safety devices and controllers need a 24 VDC SELV (Separated Extra Low Voltage) power supply. This is to maintain the integrity of the safety of the machine and to help eliminate false tripping due to inrush currents if other devices on the same supply are switched on.”
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