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ALDEH 300 Energy Harvesting Modules
Jeff LeBlanc 1.22.08
The EH300 Energy Harvesting Module is made by Advanced Linear Devices. It is designed to store sporadic electrical energy from almost any source (solar, piezo, mechanical, ...). The stored energy can be used to power circuits that run at 3.3V DC for short periods of time.
The EH300 consists of 3 basic parts: electrical power input conditioning circuit; capacitor for electrical power storage; voltage trigger to release energy when capacitor reaches proper voltage. The EH300 charges up to 3.6V, at which point it's output pin Vp will switch "on" and can power a load. Vp will stay on until the voltage drops to 1.8V, a which point the module will begin harvesting energy again.
The EH300 can store 4.6 mJ of useful electrical energy. This is approximately enough to power an LED (drawing 15mA at 2V) for 0.2 seconds. The larger EH300A can store 30mJ of useful electric energy. This is approximately enough to power an LED (drawing 15mA at 2V) for 1 second. Although this doesn't seem like much power, for small sensors or radios this can be enough to take a sample and transmit or store the data.
I tested the EH300A with a solar cell (output 4V in bright light) and in good conditions it was able to power an XBee Radio for 2 data transmissions (for those with XBee experience the settings were: D02, IT1, IR50). The pause between transmission bursts varied with the lighting conditions. In ambient indoor light, this setup did not work, though I was able to pulse a single LED once every few minutes.
The EH300/300A can be purchased from Mouser:
Due to their high costs, they won't always be the best solution for certain kinds of inputs. For example, most solar cells output steady (if low) power and a simple and cheap BEAM setup of Capacitors and voltage trigger will work fine. The EH300 will probably be most valuable when trying to harvest sporadic energy sources (such as piezo or mechanical), since it's major ability is to intelligently condition the incoming energy.