The watch is centered around the attiny85, a really small eight pin micro controller (just like the arduino, only tiny-er). The attiny keeps the time, and drives the vibration motor. A transistor is used as a motor driver to current-protect the attiny. Even though the vibration motor is small, it needs more current the the attiny can handle. Finally, there is a button to manually request the time. The entire setup is mounted on protoboard and powered by a coin cell.
This project is not only a cool watch, but a really small arduino board! That's right, the attiny85 is programmed through the arduino IDE. More on that later.
Step 1: Gather/buy Materials
-Hot glue gun
-Rotary tool or hacksaw
-Soldering iron w/solder and damp sponge
-Arduino uno or similar to program attiny.
-Computer with latest arduino IDE
-USB cable for uno
I chose not to link to distributors like digikey or sparkfun because everybody seems to have their own preference on where to buy parts, and you can buy these at almost any good online store. However, I recommend jameco. Some stuff can be salvaged easily. All are thru-hole.
-Through hole stripboard. (Look for the epoxy stuff, fiberglass is dangerous to cut)
It will be easier to follow this instructable if you use the same board then I did, you can find it at
-CR2302 coin cell battery holder.
-Small push button.
-220 ohm resistor
-3300 ohm resistor
-8 pin DIP socket
-Vibration motor (I salvaged this from an old cellphone, or you can buy one)
-Scrap hookup wire (not much is needed)
For reference throughout the build, refer to the (sloppy) attached schematic
Step 2: Add Socket and Battery Holder to Stripboard
Step 3: Populate More Components
Step 4: Jumper for Joy
Step 5: Populate Pushbutton+friends
Step 6: Solder It Up
Step 7: Power Rails
Step 8: Vibration Motor
Step 9: Program the Attiny
Flash the program file below.
Step 10: It's ALIVE
Press the button, and it should start vibrating the time! Fee free now to carve away the unused section of the board.
Step 11: It Didn't Work
First, double check the connections with the instructions and the diagram. If something looks out of place, then go back and fix that.
Use a fresh coin cell battery.
Re-upload the code and ensure that the programming was successful.
Press an LED on the power rails, negative side facing down. If it fails to light up, then the connections between the board and battery are bad.
Press an led on the top left and lower right of the atmega, negative side on the lower right pin. If it fails to light up then the connections between the chip socket and breadboard are bad, or the chip isn't oriented correctly. Remember that the dot on the attiny faces the lower left.
Press an led on the far right and far left pins of the transistor, negative side on the far right. If it fails to light up the problem lies within the transistor, if it lights up then the vibration motor is bad.
Leave a comment and I'll reply.
Step 12: Going Further/a Final Note
I did not design a band or case for this watch, so it is pretty delicate.
This watch rips through coin cell batteries at a rate of one per 10 hours, possibly some power saving firmware would help?
Because the attiny keeps track of time on its own, it is rather inaccurate. A external RTC would benefit this project, however the DS1307 needs 5 volts. Any suggestions?
A small lipo battery in place of the watch battery would save a lot of space.
On a final note, I read a story about designers who created a watch with no display and a vibrator motor instead(just like me!) but they programmed their watch to vibrate every 5 minutes, creating a unique perspective on time. I promptly copied them, the firmware is below(beware, untested) with some experimental power saving stuffs.
This is my first technology instructable, any suggestions? Please comment below.