Fire-Powered Phone Charger
Overview
This project integrates Peltier modules to convert heat generated from a campfire into electrical energy for charging devices.
Challenges & Solutions
This project was built for a university course which prompted us to build a product that harvested wasted energy. We decided to design a device that harvested heat from a campfire to charge devices while camping. This meant we had to balance performance with industrial design considerations, as it would be a consumer product. In order for the Peltier modules to work as efficiently as possible, we used a pin-style heat sink to keep the back side as cool as possible to create as big of a temperature gradient as possible. This also met the aesthetic requirements from our industrial designer.
Technical Details
I designed an electrical charging system that used an ATTiny 85 microcontroller to monitor the voltage of the system to notify the user when the device was at a high enough energy output to charge a phone and energize the USB port. This microcontroller also monitored the temperature of the device to notify the user if the device was overheating.
What I would do differently
One thing I didn't consider was the voltage sag from the Peltier modules as current was drawn. When the microcontroller detected that the Peltier modules were outputting enough voltage to energize the voltage regulator, it would energize the USB port. However, when current flowed, the Peltier module voltage would drop, and the microcontroller would cut power to the USB port. Only after the Peltier module voltage rose above a certain threshold could it support the current flow without sagging below the functional voltage of the regulator. I should account for this sag in the microcontroller programming by using a higher threshold before energizing the USB port.
