Drum sequencer (controller)

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A drum sequencer is an electromechanical system for controlling a sequence of events automatically. It is like a mechanical music-machine with movable pins, controlling electrical switches instead of musical notes.


A drum sequencer is a reprogrammable electromechanical timing device used to activate electric switches in repetitive sequences. Primarily, these sequencers were used in industrial applications to enable automated manufacturing processes. In a drum sequencer, an electric motor drives a cylinder, usually through a reduction gearbox, at a fixed speed and usually extremely slowly, or in steps (using stepper motors). The cylinder (drum) is studded with pegs along its surface, which a programmer may change or rearrange (reprogram). Much like the pegs in a music box cylinder activate 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 replaces a human operator and takes on the responsibility of performing repetitive switching and operations ideally with no weariness and fewer errors.


Unlike cam timers, drum sequencers could be reprogrammed easily. They were primarily used with industrial machines to control repetitive sequencing operations by switching associated electrical circuits mechanically. Drum sequencers are one of the predecessors of programmable logic controllers.

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