Count Down Clock
NASA has one. So should we.
Design
Wants
- Large LED 7-segment display with a +/- out front. HH:MM:SS
- You can get ~ 1 foot ones around the internet, probably better than making one.
- Something like a A6279 Constant-Current Latched LED Driver.
- Some little μc (PIC?)
- Is RTC overkill?
- Serial (for other, future devices) interface (with commands like set, start, stop)
- USB (for, say, the launch computer). Same commands as before)
- Loudspeaker to announce 'Go, flight.', countdown, and 'Guidance on internal'
Part Options
- Sparkfun red 6.5" 7 seg $14.95
- Evil Mad Scientist 12" 7 seg $55.00
- Digikey 5" green 7 seg $32.60
- Futurlec 9" 7 seg (board only) $30.90
These are more expensive than I was hoping. The sparkfun ones might be the best deal though. Still easier than making them.
Cost
| Part | Number | Cost [USD] | Total |
|---|---|---|---|
| 7seg | 6 | ??? | ? |
| Some LEDs (colons) | 4ish | 1.00 | ? |
| LED Drivers | ? | ? | ? |
| Power MOSFETs | ? | cheap | ? |
| USB driver | 1 | ? | ? |
| μc | 1 | ? | ? |
| Board | 1 | ? | ? |
Board layout
- img preview
- attach file