The P21110 Powerharvester receiver has some great new features for power management in addition to RF Energy Harvesting. A battery-free wireless sensor node (shown below) has been designed to demonstrate the improved performance capabilities of the P2110.
The sensor module has a P2110 Powerharvester, 50mF AVX BestCap, 3 sensors (temperature, humidity, light), a PIC24 microprocessor, and a 2.4 GHz radio module. This node was powered by a 4W EIRP, 915 MHz transmitter. For testing purposes, an antenna was used with a linear gain of 4, or 6 dBi. The PCB dimensions are approximately 1.5″x2.5″.
When a charge threshold of 1.25V is reached on the supercap, the DC output is turned on to power the MCU and radio. A quick read of the sensors is performed, the received signal strength (RSSI) from the transmitter is determined, and that data is transmitted using the MiWi P2P protocol. The PIC24 was programmed to use the new RESET feature to turn off power as soon as the data packet was transmitted. With the energy management implemented in this node, a significant reduction in energy consumption was achieved from a previously unoptimized, off-the-shelf sensor demo. The transmitter also has the ability to send low-rate data, such as a transmitter ID, that can be used for location-based applications or to activate only specific end devices.
The performance at different distances is as follows:
10 feet - every second
20 feet - every 6 seconds
30 feet - every 21 seconds
40 feet - every 89 seconds