Notes from the Sigfox “Connect your city” Hackathon

November 24, 2015

I attended the Connect your City hackathon organized by Sigfox and the city of San Francisco. It was absolute fun.

What is Sigfox?

Sigfox is a European company that has installed low power wide area networks across several cities in Europe and San Francisco.  Sigfox’s radio network enables interfacing low power sensors to a network enabled by radio transceivers installed in San Francisco’s public libraries.

This radio network enables transmitting a 12 byte message at a time and it is capped at 140 messages per day. This network is very useful in the case of interfacing sensors that do not provide real time updated. For example. sensors that report their status every hour or so, panic buttons that transmit emergency alerts to first responders etc.

The Hackathon

In the hackathon, teams were given the Texas Instruments Sigfox boosterpack, access to the Sigfox backend, assistance from Microsoft’s Azure team and Plasma/Connect2me. The hackathon’s objective was to build proof-of-concepts that would have a civic impact in the city of San Francisco.

My team’s project

My team picked a project that enabled collecting information related to the number of people assembled in any room of a building. This information is transmitted to the Sigfox network in the event of an earthquake (detected by an accelerometer installed in the building) or whenever a panic button is pressed.

We also used a PIR sensor, temperature sensor and a force detecting sensor to simulate events like large pillar columns falling down, buildings catching fire etc. This information could be used by first responders to effectively deploy resources in an emergency.

We built two gadgets. I built one of them and is shown in the figure below. It includes a panic button, temperature sensor and a force detecting sensor.


Gadget that I built includes panic button, temperature and force sensors

My team mate Yingxian built another radio that gathered information from an accelerometer and a PIR sensor.

photo (4)

Photo Courtesy: Yingxian Wang

The radios transmitted the messages to the Sigfox radio network. The transmitted messages were supposed to be used for visualization in a web dashboard like the one shown below.



Dashboard by Tim Strickland

How does this gadget work?

The figure below provides a simple description of how these radios interact with the “cloud”.


We got an unlimited evaluation license for our radios and our radios did not have any daily cap on the number of messages that could be transmitted to the network for development purposes.

The radios were very easy to use. They transmit any message received through the serial port. We used an Arduino Yun to interface our sensors. The Arduino Yun transmits the message to the radio via serial port. It also talks to a processor running linux on the Arduino Yun. Here is a short video of my project: It sends an emergency alert to the Sigfox network and plays an audio alert.


Here is another video where we simulated an earthquake. My teammate,  Yingxian wrote the code to detect earthquake like movements to detect earthquake simulations using an accelerometer.

My team

I met my team mates at the hackathon and I am amazed by how we were able to get along with each other. Here is a pic of my team after the hackathon prizes were announced.


Left to Right: Yingxian, me, Tim, Louis, Albert and Alex.

Who were the winners?

AudioArgus – A team that built a service that predicts faulty rotary/reciprocating equipment requiring service and alerts the city about it. I see this as a project that enforces behavior change using the Internet of Things.

Dry Water – A water sprinkler controller project that considers several weather factors to turn on/off a sprinkler. I see this one also a behavior change tool by building connected devices

There was also a bike project that enabled enhancement of bike rental experience. I am not sure that I am able to recall the project’s theme correctly.

  1. The radio network’s coverage spans between parts of San Bruno in the San Francisco Bay peninsula, Hayward in the eastern side of the Bay, parts of Marin County and Berkeley.
  2. The sketch used to transmit messages is available from here.

What next?

I had fun working on this project last weekend. This has motivated me to register for another smart city hackathon on December 5th. If you are interested in working on a similar project (not the same one) at that hackathon, you should write to me @ yamanoorsaiatgmaildotcom or ping me via twitter using the same handle.


IR and LDR sensor strips

February 26, 2010

I have attached the pictures of the IR and sensor strips that I had designed for the robotics workshop.

The board has been populated and it is ready

February 8, 2010

PICdevelopment board

The board was populated successfully and most of the functional features of the board have turned out to be successful. I am yet to test one of the two voltage comparators available on the board.

The main features of the board include:

  1. PIC16F877A platform
  2. L293D module ( Can drive 2 geared DC motors or 1 stepper motor)
  3. ULN 2003A module for stepper motors
  4. Voltage comparator circuit for LDR based sensor module
  5. Voltage comparator circuit for IR LED – photodiode based sensor modules
  6. Analog Inputs
  7. Seven Segment Display * 4nos
  8. RS232 port
  9. LED outputs to test the comparators/voltage sensors
  10. 8 LEDs to test the outputs of the individual pins of the controller
  11. Plug and play option — Can test it with simple connecting wires across any pin of the microcontroller
  12. Power supply pins to power other add-on boards

Looking foward for your comments!

Building your first development board

November 2, 2009

I had a long chat with one of my friends regarding microcontroller applications and the like.

It never occurred to me that we spend thousands on buying different components for our hobby projects and we discard them after their intended use or construct a different one for another application.

A classical example of using an electronic circuit board on a longer run is your first microcontroller development board.  Be it AVR or a PIC microcontroller, you are going to re-use them for several hobby projects.  Why not develop it as a standard platform?

There are people who sell development boards for PIC and AVR microcontrollers in the market. They provide you with standard interfaces to learn from scratch. For e.g LED Blinking, Seven Segment LED interface, LCD interface, Stepper Motor Driver, Servo Motor Driver etc. One can develop them for himself/herself, step by step.

PIC development board

The insert picture shows a PIC 16F877A board developed by me for my hobby projects. It has got the ubiquitous LED interfaced to it. Any hobbyist tests his/her microcontroller board with a standard LED blinking program to start with.

By developing one such board, I learnt interfacing the above mentioned examples. I developed all the standard drivers required for the components, myself. One day, I am planning to bring all the applications together as a product!

Why not try one for yourself?

IR Sensor using LM 311

September 22, 2009

September 22, 2009:

My IR sensor using LM311 and IR LED – Photodiode pair is done. Please see the pics below:

IR sensor circuit
The LED on the right side is the IR LED. The one on the Left is a Photodiode

IR Light

The circuit seems to work like this:

If you take a white reflective surface close to the Transmitter – Receiver pair, the light from the IR LED is reflected on the Photodiode and hence a high signal is received at the output.

If you take a black surface close to the sensor, they seem to show no response. Black surfaces usually absorb IR radiations and hence there is no effect on the output.

However, there seems to be a problem with the output voltage. The high signal seems to be a mere 1.5 V which doesn’t seem to “Switch off” the Red LED at the output instead it seems to glows dimmer. I am trying to find out the reason.

IR LED emits IR Radiations in narrow angles. So, the IR LED/Photodiode need to be placed as close as possible.

Both the IR LED and the photo diode look similar to the naked eye. To check for an IR LED, connect the LED to a battery with a 100 ohm resistor. Use a camera to observe the IR radiations from the LED. If the LED glows in shades of violet and red, Bingo! you have chosen an IR LED!

LM 311 Light activated Switch

September 18, 2009

18 September 2009:


Well, Here is my first sensor that was rolled out for my Line following Robot ‘Cyborg’. It is a Light Detective Resistor (LDR) based circuit where the resistance of the LDR drops when light is incident on it. This results in an LED glowing at the output of the LM311 voltage comparator.

I got the circuit for this comparator from Circuits Today. At present, I am facing some problems with BC107 transistor which acts a switch at the out put of the comparator. I will either replace it or remove it from the picture at the earliest. To know how a voltage comparator works, click here.

I have plans of debugging the worn out transistor, adding up one more sensor for my Cyborg as well as trying this comparator for IR transmitter pair. Watch out for more updates!

19 September 2009:

I removed the transistor and I was able to learn that the transistor while acting as a switch, inverts the output of the comparator i.e., When the LDR resistance drops, the LED goes off and vice versa which is quite opposite to its earlier operation.

I have demonstrated the application of obstacle detection using a simple video. Here, the obstacle reflects the light from the white LED on the surface of  the LDR causing a drop in resistance. This makes the output of the comparator turn high. Eventually the LED switches off!