Monthly Archives: October 2017

Wireless Temperature Sensor for Cold Storage

 

temp_snsr_node_1

We are currently testing our smallest form factor wireless temperature sensor node.

Dimensions: 50 mm x 50 mm x 10 mm.

Antenna options

  • External whip antenna
  • Internal PCB antenna

The temperature is sensed by a thermistor with 1% tolerance.  Thermistor is visible outside the enclosure

Powered by a single CR2032 coin cell battery with 220 mAh capacity and 3V nominal voltage.

Transmit power of +12 dBm

Operates in the 865-867 MHz license free India band.  Operating at this frequency has the following advantages:

  • This band is mostly free throughout India so very low possibility of interference.
  • 3 times higher range compared to 2.4 GHz (assuming same link budget)
  • Greater penetration through obstacles such as walls etc

The sensor node is  configured to operate as a reduced function device which means that the node is sleeping in low power mode most of the time, only waking up to sense and transmit temperature data if absolutely required. Sleep mode power consumption is less than 2 micro-amps.

Sensor node can send data to a WiSense LPWMN coordinator node (WSN1120CL) directly or indirectly through one or more WiSense LPWMN routers/FFDs (WSN1120L).

Each message from sensor node also reports the battery voltage.

Sensor node can be configured to –

  • Report temperature data at fixed intervals where the reporting interval can be dynamically adjusted from every 1 second to once every day.
  • Report temperature data when temperature drops below or rises above configurable threshold values.
  • Report temperature data only if temperature changes by a configurable percentage or absolute value in deg C.
  • Any combination of the above.
  • Report battery voltage and temperature data if battery voltage falls below configurable threshold.

 

For more information, please visit wisense.in.

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WiSense Asset Tagging System using Active RFID Tags

asset_tracking_sys_pic1

 

This is the latest addition to our product line. We are already deploying these at couple of customer facilities (factories).

asset-track

This asset tagging system has these components:

 

Active Tags – Each tag has a radio (sub-GHz or 2.4 GHz) and a tiny micro-controller. It is powered by a 3V Li-Ion coin battery which can last for 7-8 year assuming one beacon transmission per day.  Each transmitted beacon carries the tag’s unique 3 byte hardwired Id.  The tag has a PCB antenna.

Reader-Router Nodes – These nodes pick up the beacons received from all tags in the  vicinity and forward the same to the system gateway. These nodes have two radios each operating on a different frequency.  One radio is always listening for beacons from the active tags and the other radio is used to form a mesh network of router radios. This mesh network is used to forward the beacons and associated information (reader node “Id” and the signal strength of the received beacon) to the system gateway.  The reader-router nodes should be distributed throughout (say a factory) in such a way that each beacon is received by 3 or more nodes. This allows the system to estimate the rough location of each tag using the signal strength information corresponding to each received beacon. These nodes are mains powered with Li-Ion battery backup. A Li-Ion charger IC keeps the battery charged when mains power is available. When mains power is lost, the node gets power from the Li-Ion battery without any interruption.

System Gateway – The gateway is the asset tracking system’s to the external world.  It also maintains the mesh network of router radios.

Tag UI and database – This can be hosted locally or on the cloud.  The database will store all the beacons forwarded to the gateway. The UI shows the location of all tags in real time.

 

For more information, please contact us at rkris@wisense.in.