Body heat energy harvester

Based on LTC3108 with selectable output voltages
DC/DC converter ideal for harvesting and managing surplus energy from extremely low input voltage sources such as TEGs (thermoelectric generators) and thermopiles. The step-up topology operates from input voltages as low as 20mV. It is a power source for wireless sensor applications where a Peltier element can be used on the input side. Although any Peltier element or TEG can be used, it is recommended though, that a power source is specifically intended as power source generator.

Operation
The DC/DC converter uses a small transformer to create an ultra low input voltage step-up. It is ideally suited for low power wireless sensors and other applications in which surplus energy harvesting is used to generate system power because traditional battery power is inconvenient or impractical. The LTC3108 manages the charging and regulation of multiple outputs in a system in which the average power draw is very low, but there may be periodic pulses of higher load current required. This is typical of wireless sensor applications, where the quiescent power draw is extremely low most of the time, except for transmit bursts when circuitry is powered up to make measurements and transmit data. The converter can also be used to trickle charge a standard capacitor, super capacitor or rechargeable battery, using energy harvested from a Peltier element. A storage capacitor provides power when the input voltage source is unavailable.

This converter has two power outputs:
1. Vout with selectable voltage and
2. Vout2 which follows Vout in terms of voltage level

Output voltage level is selected on the two solder jumpers, where the following combination is used:

1+3 Vout = 5V
1+4 Vout = 4.1V
2+3 Vout = 3.3V
2+4 Vout = 2.35V

In the above image voltage selection, the selected Vout is 4.1 volts.

Connections

Please see images for board connections

S - additional storage element ( super capacitor or similar - voltage up to 5,25V)
V1 - Vout1, up to 5mA of output current
V2 - Vout2, up to 300mA output current
G - ground connection

Dimensions 22mm x 21mm
Peltier element is not part of the offer.