blueroomelectronics
- Joined Jul 22, 2007
- 1,757
I've just recently began reading through this massive thread and that's the first thing came to mind. Even though it's a moot point now I thought it would be interesting to see what I'd have done. Off the top of my head.For real flexibility consider a microcontroller solution, software is often easier to modify than hardware. The advantage of hardware is often found in speed. Here, compared to hardware speeds, your circuit can be very slow.
PIC18F4620 (cheap, common, and can be programmed in bog easy Swordfish BASIC)
I/O
28 for 4x7 segment CA displays (direct segment drive, easy PWM in software)
1 for colon
2 for 32,768Hz crystal
1 A/D for LDR
3.5 remain for RS232 based remote control (XBee, WiFly, Bluetooth), or something similar to the OPs version. IMHO I'd have gone for wired such as RS485 just to keep it reliable.
Segment drive: a series of ULN2803 or other high current NPN driver
LM2574N-5 (or ADJ if you want 3.3V) simple switcher (DIP-8 is so easy to work with, and runs very cool)
This would have been fairly straight forward to code in Swordfish BASIC and far more flexible than a non microcontroller version.