The 803-F812X Rotating Cam Limit Switch by Allen-Bradley is a heavy-duty circuit control device used with industrial machinery that has dedicated cycles of operation, in applications where the main machine’s motion corresponds to the drive’s shaft rotation. It is designed for long-lived, heavy-duty operations, and it makes use of a shaft-mounted cam, which actuates contacts as the shaft rotates. The 803-F812X comes with 8 snap-action block contacts with a 150 RPM rotating shaft and with modified double extensions and over-sized ball bearings. It also comes with a spring-loaded cam-roller that is mounted on a contact base, and 8 independent cam operator assemblies, with variable cam segments. The cam activates the circuit when the higher cam segments (lobes) pass across the cam roller, closing snap-action contacts 1 and 2 and opening contacts 3 and 4, and the circuit de-activates as the lower cam segments (valleys) pass by the cam roller.

The total duration of the activation (dwell time) corresponds to the size of the lobes, and it can be either at the maximum (when the lobe offsets at the maximum angle), or at the minimum (when the lobes are aligned perfectly), and it has a timing which corresponds to the position of the cam with reference to the keyway/TDC. The 803-F812X has external dwell and timing adjustments, which can be set or reset by using a screwdriver while the machine is in motion, and it has a cam duration range of 12 to 348 degrees. It comes in a NEMA Type 4, and 13, dirt-tight and oil-tight enclosures, and it has an operating temperature range of -22 to 150 degrees Fahrenheit, with storage limits of -22 to 200 degrees Fahrenheit. The 803-F812X weighs approximately 6.4 kilograms (14 pounds), with shipping dimensions of 177.8 x 82.6 x 312.7 millimeters (7 x 3.25 x 12.31 inches), and it is CE, UL, and CSA-certified.