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.
For each clock cycle my output for the finger using three led's looks like this (o is on, x is off), repeating:
xxx
oxx
oox
ooo
ooo
I've breadboard 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] -
[leds]
http://spacebison.com/files/fingercircuit.MOVThis 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.
I'll try to post a schematic soon. But 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.
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. And even though it looks like a total mess on the breadboard now, it'll look alot cleaner once I transfer it over to my pcb program.
thanks
