Monthly Archives: March 2017

3D printed antenna stand

This week we got a antenna stand 3D printed. The stand keeps our half-wave dipole antennas up right on a flat surface.  The antenna can be snapped in to one of three holders. Useful to have when doing some testing without using an enclosure.

I have some pics of the setup below showing a WSN1120L sensor node connected to an antenna through a U.FL to SMA cable assembly.

Thanks again to Hack Lab for help with the design and printing.









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WiSense nodes in the machine shop

Pic below shows a WSN1120L  based sensor node equipped with two float switches and  a temperature sensor for tracking the level and temperature of a CNC machine’s coolant tank.



Pic below shows another WSN1120L based sensor node equipped with an NTC thermistor for measuring motor temperature.


Both the nodes (shown above) run on a pair of AAA  batteries. The WSN1120L wireless sensor  node (in each  case) is  configured to operate as a reduced function device (RFD). The node wakes up periodically (depending on the application), samples the attached sensors, sends data to the network gateway and goes back to sleep.  The battery voltage level is also measured and  reported in every sensor data message sent to the gateway.

All the electronics is protected by a low cost weather proof enclosure.




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GSM/GPRS Modem Board

This week we tested our new Telit GL868-Dual GSM/GPRS board. The GL868-Dual is a dual band 900/1800 MHz GSM/GPRS device.

This board is suitable for providing cloud connectivity to a remote instance of a WiSense wireless mesh network. The board can work directly off a Li-Ion battery which could in turn be charged by a solar panel or even mains AC if available.

This board can be easily interfaced to a Raspberry PI using an USB to serial (RS-232) adapter. The 5V output of the Raspberry PI should be used to power the board’s comm interface (see supply (2) below).

The GL868-Dual board can also be interfaced to an external micro-controller such as the MSP430 on a WSN1120CL coordinator node. The external micro’s supply voltage can be different from the power supply provided to this board. This is possible since this board utilizes voltage translator ICs for all exposed GL868-Dual signals. The external micro’s supply voltage should be used to power the board’s comm interface (see supply (2) below).

The GL868-Dual peak current draw is around 2 Amps.


  • Power supply (1): 3.8V  to 4.2V  (Allows the board to work directly off a single cell Li-Ion battery) through 4 pin screw less terminal block.
  • Comm interface voltage supply (2) allows board to be interfaced with external micro-controller / R-PI etc through multiple voltage translator ICs. This is independent of the power supply (1) mentioned earlier.
  • Mini-SIM card holder
  • Comm interface:
    • RS-232 (TX/RX) through a  DB-9  connector
    • UART (TX/RX) on 2.54 mm pitch headers.
  • Other exposed GL868-Dual signals (through voltage translator  ICs) on 2.54 mm pitch headers.
    • RESET_M
    • ALARM_M
    • BUZZER_M
  • External signal which controls a load switch gating power supply (1) to the GL868-Dual modem.
  • Antenna  connection through u.fl connector.

PCB specs:

  • Layers: 4
  • Dimensions:  69 mm x 82 mm
  • Finish: ENIG
  • Mounting holes: 4
  • All components mounted on top side.

Here is a  pic of the board.


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Wireless Soil Moisture Sensor

We got a 3d printed enclosure for our soil moisture sensor thanks to Vikram Rastogi who runs  (co-located at Nasscom COE-IOT). This was our first experience with 3d printing and we are happy with the outcome.

The 3d enclosure has two parts. The top part can be screwed on/off the longer bottom part.

The moisture sensor is connected to a WiSense WSN1120L sub-GHz wireless node through 4 wires (2 for power and 2 for the I2C bus).

In the pic below, you can see the soil moisture sensor connected to the WSN1120L mounted inside another weather proof enclosure.


Here’s a close-up of the 3d printed enclosure.


Here’s a pic showing  the sensor in action outside Nasscom COE-IOT in Bangalore. The soil moisture data is being  sent (every  5 minutes) to our data collection/visualization application “WiSight” running  on AWS.


Here is a  snapshot of the sensor data from WiSight.


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