Simplest Attiny85 based watch

We are used to see different kinds of DIY watches. Some of them try to stuff lots of functionality, other make fancy time telling format or simply mimic smart watches. But why not build a watch that only tells time in a simple manner. This Attiny85 watch is what it does. Schematic is very simple and straight forward – Attiny85 microcontroller, 12 LEDs, push button, three resistors and coin cell battery. Such simplicity allows building small watch shaped PCB where all components are fit to look nice and light. Since microcontroller comes with only 5 I/O pins (excluding reset), LEDs are connected using smart Charlieplexing method that allows saving pins for simple I/O tasks. The only shortcoming of this watch that time is counted using microcontrollers internal clock which may not be very accurate. As author states, clock is capable of keeping time within two minutes over 24 hour period. There are ways of calibrating internal clock source by manipulating internal registers, but in the end there is no point, as oscillator is dependent on many external effects like temperature,… Continue reading

TicTocTrac – a digital watch that tracks time perception

All events in today’s world is based on time. Our day is usually planned and tied to time so we need to keep track of it. So this is a great wrist watch project designed by Cornel students Brian Schiffer and Sima Mitra. The aim of this project was not only to tell time (which is also greatly displayed) but also keep track of your time perception. It records every activity to the SD card that later can be graph plotted. By analyzing time graph you can see how well you perceive time. An you may notice that the more often you check time the slower it seems to go. Especially when you do boring tasks. Be sure to read the whole concept of this project. The rest seems to be somewhat standard – AVR microcontroller, DS3234S RTC, MicroSD, etc. They also put some effort and 3D printed a watch case that looks really geeky. Continue reading