Energy harvesting as a method of power generation for wireless sensors introduces the potential for a sustainable wireless sensor networking solution, enabling key concerns with ongoing maintenance costs and the environmental concerns with battery disposal to be addressed.
Jennic’s energy harvesting demonstrators show how energy harvesting techniques can be successfully applied to wireless sensor networking.
Use of the high-performance 32-bit RISC CPU core inside the JN5148 for fast processing, combined with the ultra low power consumption of the device in sleep and when active, enables the demonstrators to show how energy levels that might ordinarily be considered as insignificant, can be used to generate sufficient power to energise the ultra-low power nodes in a Jennic based wireless sensor network.
RF Harvesting
By combining this platform with the high performance technology from Powercast (energy harvesting partner) the demonstrator is able to show how RF energy transmitted in to the environment can be harvested to drive a sensor node in an IEEE802.15.4 standards based wireless network.
Low-Power Sensor Board
Designed specifically for purpose and with a footprint of 60mm by 35mm, Jennic's low-power sensor board for the energy harvesting demonstrators is able to take power from a broad range of different energy sources. A 40-pin socket accepts a pluggable JN5148 module. A light-dependant resistor (LDR) and a potentiometer present on the board, provide data to the microcontroller’s comparator and ADC. These can be substituted for other sensors by wired connection through jumpers. The board also features Program and Reset switches, UART access for communication with a PC, and an LED. The microcontroller provisions power for the LED and sensors to maintain minimum power consumption.
Ultra-Low Power JN5148
At the core of the demonstrator, the JN5148 wireless microcontroller handles all of the sensor measurement and control, the system energy management, and communications over the IEEE802.15.4 based network.
With an application sleep current of 3.45μA, a 61μC charge requirement for the 2.4GHz transmission (183μJ of energy at 3V supply), and significant enhancements in startup time and processing, the JN5148 requires approximately half the energy compared to a rival wireless solution.
The trace immediately left shows the energy consumption profile in the wireless solution.
Jennic - Powercast Partnership
Powercast specialise in RF transmitter and harvester systems. Within the Jennic demonstrator a 2W Powercaster and dipole Powerharvester have been adopted. With this arrangement and at a distance of around 20cm, the JN5148 can obtain continuous power for the application.
Equally, energy is stored to a level whereby the JN5148 can continue transmitting up to a half a minute later with the Powercaster powered off. In situations where a transmission is necessary less frequently, the range between the Powercaster and Powerharvester can increase significantly, to the order of meters.
The Powercaster and Powerharvester used identical omni-directional antennas with an antenna gain of approximately 1.4 (the quoted 2W power output of the Powercaster incorporates this antenna gain). The transmission frequency of 915MHz is the GSM band, the same frequency as is used for mobile internet. Being omni-directional, a single Powercaster can be used to supply power to 10+ Powerharvesters for a higher energy efficiency.
To discuss your specific application requirements, please send an email to harvesting_AT_jennic_DOT_com