wire crazy?
This is a 7 digit, 7-segmented display, utilizing several TL constant sink drivers, and the parallax propeller 32 bit, 8-core MCU. There's a TL driver for every common anode digit; communication is handled via SPI to the cascaded shift registers. The prototype is 100% wire wrapped, and surprisingly fast!
Originally we looked into using the maxim 7219, which was a single IC to drive all the segments. That particular IC is limited to 5v and something like a 60ma sink, which would never drive the 14.4 v, 100ma segments! There is a way to do it, but the transistor array and/or auxiliary maxim IC's required felt component heavy. One fun note on the 7219: it works on POV!
The Propeller MCU was chosen arbitrarily; another project will require these chipsets, so it seemed like a good idea to brush up on 'em. They are very reliable and incredibly versatile; parallax sells a kit to make videogame systems out of them! The compiler crashed on XP, but worked fine on windows 7. The language itself, is a bit clunky, but the 8 "cogs", and 80mhz speed make up for it!
Lastly, this device will count waterflow, but only once the PCB is back!
UPDATE:
Installed and operating, this device is live! It only needs a darker tint on the glass.
Here's some ktsf video with it.
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