Overview
The project uses an accelerometer to track movements as it builds a small key ring-sized alarm.
Details
During the usage, the device vibrates gently to notify the reaching of a stopping point to signify getting off the train. The right number of stops can be set by the user using a simple one-button interface which will remind when getting off is time. Due to the low cost and suitable array of features, the ATtiny13 was chosen for this project. The tilt and movement of the device can be monitored by a 3-axis accelerometer MMA7260-3. A discrete silent alarm is provided using a simple cell phone’s alarm motor.
The operation starts as the data is read from the pushbutton and accelerometer and the cell phone motor is gently pulsed with a sine wave once certain conditions are met. In order to minimize production cost, the hardware limitations were set so high in this device, since it was at the limit of I/O for the tiny13 device. As an alternative to the vibrating cell phone motor, the circuit has provision for a LED-based visual alarm. The RESET pin is designated for sleep mode.
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