HG105A6 by Danaher

The HG105A6 is an on-off repeat-cycle timer manufactured by Danaher within the Timers and Controllers series. Designed for panel installation, this electromechanical device drives two independent changeover circuits in precise succession so conveyors, heaters, or pumps can run and rest for fixed intervals without external PLC logic. In an automation panel, it converts the constant mains supply into a repetitive contact sequence, coordinating loads that require periodic energizing and de-energizing during continuous operation.

The timer operates from a nominal 120 VAC supply, and its internal circuitry imposes a burden of only 2.5 VA on that line, reducing heat inside crowded enclosures. A synchronous, unidirectional motor synchronized with the incoming 60 Hz line frequency turns the cam stack, so cycle-time stability relies on utility frequency rather than drift-prone oscillators. During each revolution, the mechanism repeats the set dwell with an accuracy of ±0.5% of the dial. Two SPDT outputs are provided, and each pole can carry a resistive load of up to 10 A at 120 VAC, allowing direct switching of most solenoids or pilot contactors. Twelve numbered screw terminals simplify wiring and separate the supply, motor, and contact circuits for maintenance.

The timer has a mechanical life of 10,000,000 operations, while the silver-alloy contact system is rated for 250,000 make-and-break cycles at the stated load. The dwell or overlap between successive contacts is limited to 1.5% of the total cycle, preventing unintended overlap currents when tightly timed sequences are needed. Operation is permitted from -20 °F up to a maximum ambient temperature of 140 °F, enabling use in unconditioned equipment rooms. A round panel cutout measuring 3.187 in accommodates the housing and provides proper support for the bezel.