Monthly Archives: February 2022

WDN110 Wireless Door Sensor

The WDN110 is a wireless door sensor operating in the Sub-GHz band. It is powered by two AAA batteries. Sleep mode power consumption is less than 2 microamps.

Multiple geographies supported:

  • FCC (900 MHz band) certified Radio
  • ETSI (868 MHz band) certified Radio
  • India (865-867 MHz band) compliant Radio

This sensor node report’s the state of the door (open or closed). It runs on 2 AAA batteries which can last many years since the node stays in ultra low power mode consuming a few microwatts except when it has to communicate with the associated network gateway.

Sensing Element

The door sensor utilizes an SPDT (Single Pole Double Throw) reed switch which opens or closes under the influence of a magnetic field. The SPDT configuration makes the sensor more power/energy efficient compared to door sensors which use a SPST (Single Pole Single Throw) reed switch.

SPDT Reed Switch

The SPDT reed switch enclosure is 3D printed. It connects to the sensor node PCB over a three wire cable. This connection is ESD protected.

We also offer a single sensor node with temperature, RH and door sensors.

Installation

  • Open the node enclosure, insert two AAA batteries and close it.
  • Stick the magnet on the edge of the door frame. It should be placed vertical to the ground.
  • Stick the switch on the edge of the door as close as possible to the magnet.
  • Place the node enclosure as high as possible with the antenna perpendicular to the ground.
  • Switch on the node. It will automatically connect to the gateway and start sending whenever the door is opened or closed.

Reporting Algorithm/Logic

The firmware on the sensor node runs can be configured to :

  1. Report every time the door opens or closes.
  2. Report only when the door is left open for more than a (configurable) duration. In this case, the node will send door state report at a higher frequency until the door is closed.
  3. If the door state does not change for a long time, the node can be additionally configured to send a report conveying the current state of the door after a configurable interval of inactivity. This message then serves as a keep-alive indication to the end application (local or cloud resident).

If the node is being used to monitor say a refrigerator or freezer, the door sensor reports will be useful in explaining changes in measured temperature.

Note that each report message also includes the supply voltage from the two batteries (connected in series).

WiSense Gateway

This node sends door state change alerts via a WiSense gateway. This gateway has multiple interfaces such as WIFI, RS-232, RS-485, serial over USB.

The gateway will report the door state to the configured endpoint which can be local or in the cloud. Supported standards/formats include MQTT, JSON, HTTP, HTTPS etc.

A single gateway can support up to 64 sensor nodes of different types. Each sensor node has a IEEE assigned globally unique 64 bit MAC address. Each sensor on a sensor node has a unique 8 bit ID.

The WiSense low power sensor node network supports both mesh and star configurations.

For more information, visit wisense.in.