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7400 competition entry: Discrete logic POV clock

Posted on Wednesday, October 5th, 2011 in 7400 contest, POV Toy by Ian

Matt’s entry in the Open 7400 Logic competition: Discrete logic POV clock.

This persistence-of-vision clock was built entirely out of discrete logic chips. The design consists of three boards, a LED array and a drive motor. The digit board keeps the time while the display board controls the LEDs.

The digit board

Every second, a pulse increments the value stored in a counter.  When it overflows, the next counter is incremented.  Each counter represents a digit in the time.  A decoder selects one digit at a time and puts that digit’s value on the output bus.

The display board

A pulse from an external source wakes up the display board.  It selects the leftmost digit from the digit board, formats it for a 7-segment-display, and chops up the result into a 5 x 5 pixel matrix. It lights up LEDs for each column in sequence then selects the next digit to the right.

Via the contact form

This entry was posted on Wednesday, October 5th, 2011 at 6:00 pm and is filed under 7400 contest, POV Toy. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

4 Responses to “7400 competition entry: Discrete logic POV clock”

  1. Arthur Benemann says:

    Cool project man, well done!

  2. Matt Swann says:

    Thanks Arthur! It was a great learning experience.

  3. Shashank Patil says:

    i hope doing it …………in order to respect those IC which gave birth to controllers

  4. Jose Rodriguez says:

    55001901 DISCRETE LOGIC BOARD V2

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