Vision-Based Operator Attention Interlock for a Test Station

The challenge

At the test station, a cycle could be started while the operator was turned toward the racks or the conveyor instead of the part in front of them. On a line testing CNG cylinders and tubes, that is both a safety risk and a quality risk. The fix had to work under the plant's changing light and glare from bare metal, run without a PC on the shop floor, and plug into the Mitsubishi PLC already controlling the station.

What we did

We mounted an OpenMV H7 Plus camera over the station and defined a green zone around the part under test. The camera checks that a face is present, that it sits inside the zone and that the head is turned toward the fixture, and that this holds steady for a fraction of a second before it raises a start-permission signal to the PLC. If the operator looks away or leaves, the signal drops and the cycle cannot start. Everything runs on the camera itself: it starts in auto mode on power-up, shows its status on a display and logs every decision.

What we built

• Start permission only when the operator faces the part inside the green zone
• Head direction held steady for 300–500 ms to avoid false starts
• HIGH / LOW output wired to the Mitsubishi PLC's start-permission input
• Runs entirely on the OpenMV H7 Plus, no PC or extra compute
• Auto mode on power-up, with a live status display and a full decision log
• Tuned for shifting shop-floor light and glare from metal surfaces
• Simulated and tested against the station layout before installation