Monthly Archives: August 2015

Smart community use case – Wirelessly controlled watering of green areas

We recently begin installing a network of wireless enabled electronic water valves in Pruksa Silvana which is a relatively new residential community in Bangalore. Widespread adoption of such systems will lead to conservation of water, especially in cities in Bangalore, where water is fast becoming a scarce resource.

The system comprises a set of wireless electronic valves which can be remotely controlled. Each of these valves is interfaced to a WiSense WSN1101L low power sub-ghz wireless node. All these nodes are wirelessly connected to a WiSense coordinator node (WSN1101C) installed inside our office. There is a relaying node on the terrace since the “valve” nodes are not in direct line of sight of the coordinator node.  All these nodes create a sub-ghz mesh network operating in the license free 865-867 MHz band in India.

The installed electronic valves are used to control the release of STP treated water reserved for use in the green areas of this community. These wireless enabled electronic valves will be replacing all the manual valves spread out through out the community.

Here are some pics of the system and it’s components:

Pic 1 - A View of the in-line installed valve.

Pic 1 – The solenoid valve.

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Pic 2 – A view of the installed solenoid valve.

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Pic 3 – A view of the solenoid valve.

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Pic 4 – A view of the solenoid valve.

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Pic 5 – A view of the transmitter node.

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Pic 6 – A close-up view of the transmitter node.

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Pic 7 – The power source used (12V Battery)

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Pic 8 – A view of the complete system.

Pic 9 - An image of the relaying node installed on the terrace.

Pic 9 – An image of the relaying node installed on the terrace.

Here, we are using a 12 V lead-acid battery to power the node and the valve. We are going to add a recharging circuit to charge the battery (from the street light) when the latter are powered on at night.

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WTN155 – Wireless Temperature Sensor

We are introducing a new product, the WTN155, a wireless temperature sensor.

Pic 1 - WTN166

WTN155

WTN 166 - Isometric View

WTN 155 – Isometric View

The temperature sensor is a Vishay NTCALUG02A series NTC Thermistor. This sensor is interfaced to a WSN1101L WiSense low power wireless module.  All the electronics is inside an IP-65 weatherproof ABS enclosure. The thermistor is exposed.  The node is powered using 2 AAA batteries. Note that the WSN1101L can be programmed using the low cost EXP-MSP430F5529LP. You can add any sensor to this node.

The node operates in the license free 865-867 MHz band in India. Transmit power is +10.0 dBm. Over the air raw data rate is 10 kbps. The sensor data reporting interval can be remotely configured (via the network coordinator) using the gateway app. By default, the node will send the latest thermistor measurement and the supply voltage in each “sensor report”.

The node has a high quality half wave dipole antenna (as shown in the pics above). We also offer a shorter quarter wave dipole antenna.

Sleep mode power consumption is less than 2 microamps.  Power to thermistor’s signal conditioning circuit is gated by the microcontroller (MSP430) using a mosfet.  This mosfet is turned off by the microcontroller before entering sleep mode.

The node is programmed to operate as a reduced function device (RFD). RFDs do not take part in mesh routing.

Shown below is a snapshot of the temperature data sent by an WTN155 installed in a server room. WiSight is our data storage and visualization tool running on AWS. You can see the saw tooth pattern created by the A/C thermostat which is maintaining the room temperature at around 19 deg C. The WTN155 is sending temperature and battery voltage data to a WiSense coordinator node installed outside the server room. The coordinator node is connected to a Raspberry Pi (which is in turn connected to the LAN). The Pi is forwarding the sensor data to WiSight.

temp_graph

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