Build It: The Electronic Post-It Note
Who needs pen and paper? Jot down reminders on a digital screen, using only your finger
“Pick up milk.” “Feed dog.” “Finish homemade nuclear sub.” Like many people, I can’t function without writing little reminders to myself. But using one paper sticky note after another causes a lot of clutter and can be pretty wasteful. Instead, assemble a bunch of surplus parts into a digital note system for your kitchen or office. Just write out your message with your fingertip on a computer trackpad, and it appears on an LCD screen.
When you’re done, press a button and the screen is erased. Add a rechargeable battery and an enclosure, and you have unlimited (and eco-friendly) note-making capability. The project does require some computer code to drive the LCD; you can copy it here. If you can just remember that, you’ll be good to go.
TIME: 7 HOURS
- (1) LCD + carrier board (SparkFun Electronics #LCD-00569 + #LCD-00600; $19.95 + $18.95)
- (1) Trackpad (Electronic Goldmine #G1283; $1)
- (1) Microcontroller (Parallax #28803; $99.95)
- (1) PAK-XI Mouse Coprocessor (AWC #PAK11; $23.49)
- (1) 3.3V voltage regulator (SparkFun Electronics #COM-00526; 1.95)
- (1) 10mF electrolytic capacitor (SparkFun Electronics #COM-00523; $0.45)
- (4) 10K resistors (RadioShack #271-1335; $0.99)
- (1) 9V battery $3 (available locally)
- Hookup Wire (RadioShack #278-1224; $5.99)
- 1 Solder wires to the trackpad’s [A] PS/2 connector.Connect them to the mouse coprocessor, which translates finger movements on the trackpad. Connect the coprocessor to the microcontroller [B] so the program code can generate an image on the LCD screen [C].
- 2 Follow the data sheet instructions on sparkfun.com to attach the voltage regulator and electrolytic capacitor to the screen. This adapts the screen’s power to the right level.
- 3 Plug the screen into the carrier board. Solder resistors to the board, and connect them to the microcontroller. Power the board by connecting pins to the voltage regulator.
- 4 Download our code for the screen at popsci.com or, if you substitute other components, from sparkfun.com.
- 5 Install a nine-volt battery. Program the microcontroller with the code from your PC. Test the device’s operation, put it in a custom-built box, and forget about those sticky notes. (NB: Screen image in above picture is simulated.)
_NOTE: A BASIC Stamp BS2 microcontroller is way too slow for adequately driving this project. The microcontroller used in this project was salvaged from an old Parallax Boe-Bot robot kit. Better performance could be obtained from AVR or PIC microcontrollers. In retrospect, I wouldn’t even consider using a BASIC Stamp for this project. If you do, you’ll be disappointed. Therefore, please consider this PBASIC code as a “starting point” for building a better digital notepad.