Classes > Output Devices
This week I want to build an audio and light beacon for my final project. My high elevation baloon tracker sends its GPS position by radio and by SMS, but for example if you land in a forest, the GPS can be innacurate and have an error of 100m or more, so it can be difficult to find the device if stuck on a tree or a rooftop, etc.
So I want to build a device that when the tracker lands (fixed altitude smaller than certain value), outputs some sound and light to help finding the tracker.
The design will be based on a small microcontroller that will generate the sound using a small piezo and a high luminosity LED. The sound and light pulses will be morse code for the name of the tracker.
This small board will receive a signal from the main controller unit of the tracker, a usually "high" signal. If this signal goes low, the beacon starts. The bacon will have it's own power supply (small battery). This way, the beacon will work even if the main system runs out of battery.
This unit will handle two speakers and two LEDs on opposite sides of the tracker, to prevent that the landing will cover the speaker and the LED.
The board is based on an attiny84 (needed the extra space for the morse table and conversion routines), driving the leds using a digital output (sinking current), and the speaker using PWM. I used timer0 to create a square wave of 700Hz, the most used tone for morse signals. It has a connector for the digital signal coming from the main board, and another one that connects to the speakers and LEDs.
Then there are two twin boards with the LED and the speaker, they have connectors on each side to make a pass-trough of the LED and speaker signals
Hardware:
Firmware: