Overview
The goal of this is to design a simple watch made from a single PCB and a watchband. In this initial version the time will be told using an RGB LED to tell an approximate minute time in color, and 4 LEDs to tell the hour precisely in a binary encoding.
Design Specification
Goals
- All Surface Mount.
- Easy enough to solder to act as an intro SMT soldering board.
- Battery Life of 3+ months, preferably closer to the 1 year mark.
- Simple and novel watch design
Features
- 4 bit binary hour counter, with LEDS.
- RGB LED to tell part of hours
- 3V coin-cell Battery Supply
- 1 Button, to bring up and set display.
- 32.768 kHz Crystal Oscillator driving an asynchronous clock
- Utilizes low-power modes, for long battery life.
Time Display "Protocol"
I have spent a little bit of time designing a basic time display methodology. 4 LEDS represent the hour in binary form. The RGB LED represents the part of the hour divided up into 10 separate states as follows.
| Colours (R,G,B) | # of Minutes Passed |
|---|---|
| R | 0 |
| R G | 10 |
| G | 20 |
| G B | 30 |
| B | 40 |
| R B | 50 |
Basic Layout
This is just a basic layout prone to be changed a lot.
Preliminary Parts List
| Reference | Description | Distributor | Distributor # | Manufacturer | Manufacturer # | Datasheet Link | Quantity | Cost Per Part | Cost Per Board |
| na | ATTiny24A Microcontroller | Digikey | ATTINY24A-SSU-ND | ATMEL | ATTiny24A-SOIC14 | http://www.atmel.com/Images/doc8183.pdf | 1 | 1.01 | |
| na | Side Actuated SMT Buttons | Digikey | P12279SCT-ND | Panasonic Electronic Components | EVQ-P7C01K | http://industrial.panasonic.com/www-data/pdf/ATK0000/ATK0000CE20.pdf | 1 | 0.74 | |
| na | Green 0805 CHIPLEDS | Digikey | 475-1410-1-ND | OSRAM | LG R971-KN-1-0-20-R18 | http://catalog.osram-os.com/catalogue/catalogue.do;jsessionid=B38D4035738FAE714C474120326E9384?act=downloadFile&favOid=02000002000009ee000100b6 | 4 | 0.09 | |
| na | 32.768kHz Crystal Oscillator | Digikey | 300-8663-1-ND | Citizen Fintech Miyota | CMJ206T-32.768KDZF-UT | http://cfm.citizen.co.jp/english/product/pdf/CMJ206T.pdf | 1 | 0.83 | |
| na | LED CHIP RGB 3.2X2.7X1.1MM SMD (1210) | Digikey | 516-1795-6-ND | Avago Technologies US Inc. | HSMF-C114 | http://www.avagotech.com/docs/AV02-2451EN | 1 | 2.03 | |
| na | 20pF Capacitors | 2 | |||||||
| na | RESISTORS! | ||||||||
| na | RESISTORS! | ||||||||
| na | RESISTORS! | ||||||||
| Battery Holder 2032 | Digikey | BC2032-E2-ND | MPD | BC2032-E2 | http://www.memoryprotectiondevices.com/datasheets/BC2032-E2-datasheet.pdf | 1 | 0.74 |