Cam timer

A cam timer or drum sequencer is an electromechanical system for controlling a sequence of events automatically. It resembles a music box with movable pins, controlling electrical switches instead of musical notes. An electric motor drives a shaft on which is arranged a series of cams or a drum studded with pegs along its surface. Associated with each cam is one or more switches. The motor rotates at a fixed speed, and the camshaft is driven through a speed reducing gearbox at a convenient slow speed. Indentations or protrusions on the cams operate the switches at different times. By arrangement of the cams and switches, complex sequences of opening and closing switches can be made. The switches then operate different elements of the controlled system - for example motors, valves, etc. A programmer may change or rearrange (reprogram) peg or cam positions. Much like the pegs in a music box cylinder activate the notes, in a drum sequencer, as the drum of the sequencer spins, the pegs run across switches activating machine processes. The placement of the pegs along the length of the cylinder determine which switch along the length of the drum it will activate. Where the peg lies along the circular circumference of the drum determines at what point in the spin of the drum the peg will activate the switch. By controlling the timing and sequence of switches, the drum performs repetitive switching operations. Most cam timers use a miniature mains synchronous motor to rotate the mechanism at an accurate constant speed. Occasionally more complex timers with two motors are seen. A drum sequencer is a re-programmable electromechanical timing device used to activate electric switches in repetitive sequences. Primarily, these sequencers were used in industrial applications to enable automated manufacturing processes. Cam timers and drum sequencers were primarily used with industrial machines to control repetitive sequencing operations. The cam followers often operated hydraulic valves.