BRUSSELS, Belgium – Silicon Laboratories Inc. has produced a wireless sensor node (WSN) reference design based on its Si10xx wireless microcontroller (MCU) family and powered by a solar energy harvesting source.
Although systems powered by harvested energy sources have existed for many years, developers have been challenged to implement wireless sensor nodes within very low power budgets.
The thin-film battery used in the reference design has a capacity of 0.7-mAh. In direct sunlight, the battery can be recharged fully within two hours. While in sleep mode, the wireless sensor node will retain a charge for 7,000 hours. If the wireless system is transmitting continuously, it will operate non-stop for about three hours, although it is designed to constantly recharge itself at an appropriate level to keep the thin-film battery from completely discharging.
Silicon Labs' design includes wireless network and USB software and a complete circuit design with RF layout, bill of materials (BOM), schematics and Gerber files. The design consists of three components:
A solar-powered wireless sensor node that measures temperature, light level and charge level, using an Si10xx wireless MCU to control the sensor system and transmit data wirelessly and a thin-film battery to store harvested energy.
A wireless USB adapter that connects the wireless sensor node to a PC for displaying sensor data; the adapter features Silicon Labs' Si4431 EZRadioPRO transceiver with an MCU running USB-HID class software and EZMac wireless software stack.
A wireless sensor network GUI that displays data from up to four sensor nodes.
An on-board bypass connector gives developers the flexibility to bypass the solar cell and tap other energy harvesting sources such as vibration (piezoelectric), thermal and RF.
The arrangement is suitable for use in home and building automation, security systems, industrial control applications, medical monitoring devices, asset tracking systems and infrastructure and agricultural monitoring systems, Silicon Labs said.
"By combining ultra-low-power wireless MCU technology with a state-of-the-art energy harvesting system, Silicon Labs has delivered the industry's most energy-efficient, self-sustaining wireless networking solution," said Mark Thompson, vice president of embedded mixed-signal products at Silicon Labs, in a statement. It was not disclosed from where the solar cell is sourced.
The Silicon Labs energy harvesting reference design is priced at $45.