LED as Energy Harvester

In some applications, solar cells are too expensive. LEDs or photodiodes are a low-cost alternative. We use them to convert light into electrical energy. They are not as efficient at this task as conventional solar cells since they are not designed to work as harvesters. In this example, enough energy can be accumulated with four LEDs to start up a microcontroller, perform the needed measurements and send some data bytes via Bluetooth Smart. This makes LEDs well suited as harvesters in applications, where it is enough to transmit small amounts of data every 1 to 10 minutes. We have also used photodiodes in a similar way.