Each row is switched on in sequence (S1, then S2 and then S3) and the corresponding switches S4, 5, 6 and 7 closed in synch to switch on the desired LEDs. To fool the eye into seeing a continuous display the sequencing is typically done at more than 50 times per second. Current flows through (1), (2) and (3).Ī practical circuit uses tranistorised switches. By closing switches 2 and 6 we can turn on LED 7 alone. In practice some form of current limiting is required. Each LED can be turned on individually by closing the appropriate row and column switches. Multiplexed displays using seven-segment LEDs remain popular due to low cost and high brightness. The advantage is simplification of hardware due to the reduced number of pins required. Multiplexing is a technique used to connect devices – typically LEDs (for displays) or buttons (for keyboards) – in a matrix of addressable rows and columns.
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