Summary of Energy Harvesting Circuit
This article describes an energy harvesting circuit using the LTC3108 DC/DC converter to power devices from body heat via a Peltier generator. The system stores energy in a supercapacitor, lighting an LED once a threshold voltage is reached. It supports multiple output voltages and can charge batteries or utilize other sources like solar cells and piezoelectric generators.
Parts used in the Energy Harvesting Circuit:
- LTC3108 ultra low voltage DC/DC step up converter chip
- CoilCraft LPR6235 1:100 coil transformer
- Peltier thermo-electric generator
- 5.5V 1F supercapacitor
- LED
- Rechargeable batteries (optional)
- Solar cells (< 0.5V)
- Piezoelectric generators
- Small motors
Recently, I built an energy harvesting circuit based on an ultra low voltage DC/DC step up converter chip (LTC3108) from Linear Technology. With a 1:100 coil transformer (CoilCraft LPR6235), it converts the tiny voltage generated from Peltier thermo-electric generator into high enough level to drive small circuits.
In the following video, I demonstrated that body heat is enough to power a LED. When there is a temperature difference between the two sides of the Peltier module, electricity is generated. A 5.5V 1F supercapacitor is used as energy storage. Initially, the super capacitor was fully discharged. As the energy harvesting circuit stores the electricity generated from body heat, the voltage across the capacitor continues to rise. When it reaches the threshold voltage, the LED turns on.
When my palm moves away, the Peltier module stops generating electricity. The LED continues to turn on until the energy stored in the super capacitor is fully depleted.
Other than super capacitors, LTC3108 could trickle charge rechargeable batteries. In addition, other energy sources like, small solar cells (< 0.5V), piezoelectric generators and small motors could be used.
There are 4 different output voltage levels that could be selected: 2.35V, 3.3V, 4.1V and 5.0V. It is flexible enough to drive small micro controllers (like Arduino, Teensy, etc.) and sensors.
For More Details: Energy Harvesting Circuit
- How does the circuit generate electricity?
Electricity is generated when there is a temperature difference between the two sides of the Peltier module. - What component is used for energy storage?
A 5.5V 1F supercapacitor is used as energy storage. - When does the LED turn on?
The LED turns on when the voltage across the capacitor reaches the threshold voltage. - Can the circuit drive microcontrollers?
Yes, it is flexible enough to drive small micro controllers like Arduino and Teensy. - What are the selectable output voltage levels?
The four different output voltage levels are 2.35V, 3.3V, 4.1V and 5.0V. - Can rechargeable batteries be charged by this circuit?
Yes, the LTC3108 could trickle charge rechargeable batteries. - What other energy sources can be used besides body heat?
Other sources include small solar cells, piezoelectric generators and small motors.
