I've been working on this project off and on (more of the former than the latter) since the last update. The basic idea is the same although some of the details have changed. For example. the chip I was using to drive the LCD wasn't very good for the task (it turns out LCD elements aren't supposed to just be turned on, they are supposed to be pulsed on and off very quickly). So I switched to a different display driver which made this easier to do. To drive the signal off and on, I needed another clock, so rather than adding another 555 timer, I used a 556 which has two timers on it. Finially, the method I'm using to get randomness out of the voltage regulator has changed again -- I'm using a transistor to amplify it. The device works in that it displays numbers that are apparently random, but I have doubts -- it looks like the circuit that's supposed to be random is just a really fast oscillator, so it's not truely random. However, the whole shebang now runs off a 20mm coin Li battery, and includes a smaller LCD, so progress is being made... slowly.
I now have a working prototype using an LCD display, instead of an LED display. Pictures and schematics to come. Here are the datasheets that matter.
Well, it's all working, but not correctly yet. The LEDs draw enough current to change the voltage across the battery enough to screw up the analog part of the circuit. Because there's a capacitor between the op-amp input and ground, I can't use the op-amp to reject these voltage fluctuations. I'm reworking the analog part to get around this problem... I'll post more information when it's working...
