An Electromechanical Tea Timer
Build Date: 2006
This was my first microcontroller based electronic project (finished in 2006). It is an electromechanical tea-timer which allows to brew your perfect tea each and every time.
It uses very basic DIY linear guides and a DC gear motor to place a tea bag or tea strainer into a water filled cup. After a user defined time period it is removed from the cup and an acoustic alarm signal is emitted. The project is build around an Atmel ATmega8 microcontroller and the firmware is written in assembly language (only in order to learn how this works).
The project is based on an Atmel ATmega8 microcontroller and consists of a straightforward circuit with relatively little amount of additional parts. The DC gear motor is driven by a L293D motor driver which already includes the free wheeling diods. To measure the lower and the upper stop positions for the linear movement two TCRT1000 reflective optical sensors are used. The user interface consists of four push buttons and a 2×16 character LCD display with backlight and a HD44780 compatible controller. The alarm signal is emitted by a piezo buzzer. All of this was build up on a stripboard.
The software was written in assembly language. Not because this is particularly useful for such a project (speed and size does not matter in this project whatsoever) but rather to learn a new technique and to thoroughly understand the microcontroller internals.
The mechanical part of this project was probably the most time consuming and difficult one, especially since good workshop equipment was largely missing at that time, and all was done with a saw and a hand drill. More details on the mechanical components will be given shortly.
Since this was my first project, the software and the schematics are quite ugly. Therefore, I do not publish them here, but if you are interested, write me an email and I’m happy to send them to you.
Tobias Schmidt <firstname.lastname@example.org>