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Energy Harvesting Evaluation 

Wireless sensors are sometimes located so remote that replacing batteries is not an option. Such applications often turn to energy harvesters. Energy Harvesting (EH) also known as energy scavenging for small electronic and low power electrical devices uses ambient energy to provide electrical power, eliminating dependency of battery power, thus they work autonomously for years. 

In general, applications by EH sources like light, vibration, RF, thermal or chemical/biological are not only low power (in micro to milli watt level) but they are at low voltages. Since most current wireless sensors, including power conversion circuits, require 2+ volt range, we have two possible ways to meet those application requirement. One, the harvested voltage must be boosted and transfer energy as efficiently as possible. Two, the application requirement must buck down to subthreshold level to match with the harvested voltage.  Since second option involves newer chip designs and it is complex, the current proposal will focus on the first option. 

In theory the systems and methods using multiple energy generators connected to the same energy harvesting circuit should result in more energy. However, if multiple sources are attached to the same circuit in an attempt to produce more electric energy, the energy loss will be very high and there will be less energy harvested than if a single source was used. The main reason for this is impedance mismatch in circuits that consumes all or a part of generated resource. Also, further losses occur due to the destructive electric signal interference results in less energy available. For these reasons, traditional single energy management circuit can only handle one energy generator at a time. 

We offer a solution that allows all EH sources to be stored at once by using an efficient energy management technique.

Wireless Strain/Temp Gauges 

WN128 series products

WN128 series is programmable wireless sensor system based on IEEE 802.15.4 (ZigBee) and off-the-shelf strain sensors to measure structures deformation just like wheatstone bridges equipment.  WN128 series monitor the strain sensor's resistance change. Users require installation of the strain sensor to a structure with special epoxy adhesive. WN128 series products support following strain measurment. 
  • 2 ¼ bridge configurations
  • 2 ½ bridge configurations
  • 2 Full bridge configurations or 2 Wheatstone bridge configurations
  • Low temp and gain error of less than 1 ppm/°K
  • Wide temperature performance, -20 ~ 85°C
  • Low measuring current of less than 100 μA at the sensor
  • Accuracy equivalent or better than 24 bit A/D converter up to 1,000 μ-strain
  • Many measuring related parameters are configurable
  • Normal range is about 15 meters

Product Summary

Application Summary

Note: Each sensor module can take multiple ¼, ½ and Full bridge configurations (see application section for the detail). 

Cases 1 - 3: We recommend to purchase WN128 set. 
Case 4: We recommend to purchase WN128 development kit. 
Cases 5 - 8: Please contact us since SDIO version is not the same as USB version. 

Each WN128-USB supports 

  • Auto end device find and bind

  • K factor input for strain gauges (This is given for each strain gauge)

  • Real time graphic display for strain change (per location)

  • Sample and data transfer rate adjustment


WN128-USB Limitations 
  • Maximum sampling rate is reduced when using multiple sensors simultaneously

  • USB hot-plug is not supported (do not remove USB dongle while it is in operation)

  • Supports Windows XP / Vista only (USB driver available for development in other platforms)

Each WN128-SDIO supports 
  • Coordinator, router and end device selection

  • Auto end device find and bind

  • Samples selection

  • K factor input for strain gauges

  • Graphic display for strain change

WN128-SDIO Limitations 
  • Supports Windows-based PDA only

  • Please contact us for PDA compatiblity

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