SN74HC157: Use SN74HC157 as a Quadrature Decoder

Stephen Katz

Part Number: SN74HC157
Other Parts Discussed in Thread: SN74LVC1G79, TIDA-00580

I was told by my distributor that I can use the SN74HC157 as a Quadrature Decoder.

How do you recommend it be configured. My input is a 2-phase rotary optical encoder, I need a two bit output or a single bit with a direction indicator.

Thank you,

over 5 years ago

0 Clemens Ladisch over 5 years ago

Guru 278800 points

The typical discrete-logic implementation of the direction indicator is with a D-type flip-flop (e.g., SN74LVC1G79). (But nowadays, you'd use a microcontroller instead.)

It is possible to construct a flip-flop from muxes, but that would be needlessly complex. You'd have to ask your distributor what they actually meant.

Also see https://www.cui.com/product-spotlight/capacitive-incremental-encoders#2 and https://electronics.stackexchange.com/questions/292334/telling-which-way-a-ky-040-rotary-encoder-has-been-turned, and TIDA-00580.

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SN74HC157: Use SN74HC157 as a Quadrature Decoder