LED controller

Discussion in 'The Projects Forum' started by spacebison, Jan 18, 2009.

  1. spacebison

    Thread Starter New Member

    Jan 18, 2009
    I've been entertaining recently the idea of making my own Boston Bomb with a few enhancements like an animated finger. Given the size of the pcb, space is not particularly an issue, but I'd thought I'd run it by and see if for this part of it, it could be simplified any or if I've missed something.

    I've breadboarded it using 4 different 74xx series chips plus a 555 timer for the astable clock pulses. It pretty much goes:
    [555 timer] -
    [7490 counter, resets at 5] -
    [74138, 3 to 8 decoder] -
    [7404 inverter, to flip the 74138's output] -
    [7432 OR gate, for lighting up the current number and those below it] -

    This video shows my current mess, the led on the left is the clock output. The leds on the top is the output I'm using for the finger taken from the output of the decoder and the OR gates shown on the led bars on the bottom. Also, it's not shown but it's set up so that on the last OR gate if one of the inputs is set to high, then all the leds will light, regardless of the clock cycles. The extra two ic's on the board were only used to fill the rest of the led bar out and won't be needed.

    Here's the output I want, as provided by my circuit. And it just repeats itself continually. If you can imagine a finger in 3 sections from closed to extended. led 1 is at the bottom, led 2 is the middle, and led 3 is the top.

    logic table:

    here's the schematic:

    I realize that a microcontroller would be perfect for this, but I don't (yet) have much experience working with them, nor would it seem to be any more cost effective to use one as this won't cost more than $2, and besides I've got bunch of 74xx chips around here anyway.