This design challenge is nearing its final deadline so the pressure as been building to complete the project.

I finally finished building all the hardware and all the hardware is working well.

The past week has seen a lot of 3D design work and 3D printing and mechanical building, but also powered up the full system for the first time.


The subscriber power monitor is showing 5.08 volts at 10 mA.

The publisher power monitor is showing 4.97 volts at 190 mA.


Here are the four instruments that make up the Invisible Hazardous Environmental Factors system.


Note the 2 USB power monitor modules are not part of the system - I was just checking how much current the systems consume.

(10 mA and 240 mA respectively)

If you look closely - you can see the CO2 is reading 463 ppm, which is bang on - a really nice quick sensor.


Here are the 4 IHEF instruments on one forearm. They barely fit.


Here is the IHEF system running. After wearing the system around for a while I am re-thinking my desire to build a Pip Boy - the weight of the full system is non-trivial.

There are a lot of LEDs on the embedded modules - I like the way they shine through the plastic housings. You can just see the green coming out the side - the yellow are mostly visible in the video.


As with any project of this complexity, there was a lot to learn and a lot of issues to work through, but on all the major tasks careful planning and design paid off.

The plusses

  • I was able to successfully design a custom sensor Booster Pack and it worked flawlessly, which was a huge benefit as there is not really time and money to spin multiple custom PCBs in a project like this.
  • The EXP432P401R MCU card was powerful and easy to program with lots of onboard resources - sometimes new products have only rudimentary documentation, but this card was well done.
  • I had purchased a second MCU card as a spare, which didn't turn out to be needed so I was able to convert it into a remote MQTT subscriber/display.
  • The CC3100MODBOOST Wi-Fi modules (I had to buy a second one for the MQTT subscriber) worked great - there were challenges for me to get familiar with it but it was well supported.
  • I learned a bit about MQTT - I'm still a neophyte, but I fully expect to use this technology in future projects.
  • I learned a lot about radiation and Radon
  • I learned a lot about the hazards of ultra violet light and electric fields, and what is important about various invisible gasses such as carbon monoxide and carbon dioxide.
  • I was able to design and print twenty-seven 3D objects to package four instruments into robust wearable systems.
  • The CO2 sensor works very well - much better than expected

The not so plus issues

  • I ordered the wrong RF sensor module (it couldn't measure Wi-Fi or Bluetooth) so I had to buy a meter instead. (the meter works great)
  • The VOC (volatile organic compounds) sensor I ordered, never arrived, but I added alcohol instead. (VOC can be substituted when it arrives - alcohol is more fun to test anyway)
  • The large complement of Booster Packs supplied with the kit had some conflicts with pin assignments, making it problematic to use all in the same system. (I'm happy with the set I was able to stack up - it made the system easy to connect electrically)
  • I did not implement my MQTT broker on a Raspberry Pi, because by the time my RPi3 finally arrived, I was well into testing with mosquitto on a PC.


The project and plan morphed a bit based on what I learned along the way, but all in the interests of achieving the primary objectives.

The project did cover the hazards of invisible environmental factors, how to measure them and what can be done to minimize them.

The project did manage to use 6 TI modules, including 2 of the EXP432P401R MCUs.

The project did end up to be fully functional, robust, wearable and useful. I already have multiple requests to borrow it - and it has only been working for a matter of hours.

Overall the project was both fun and educational, even though I don't generally enjoy dwelling on dangers and hazards.

I've enjoyed experimenting with lots of TI modules in the past but EXP432P401R MCU is going to be my new favourite for complex microcontroller projects - this project didn't even cause it to break a sweat, either in speed or resources. It is easy to use and the price is attractive for an ARM Cortex M4 module.

If you are thinking about entering a design challenge like this, I heartily recommend it - there is tremendous satisfaction in completing such a project.


Next Steps

Although the system is complete, I still have some time and some tasks I would like accomplish:

  • clean up my sensor program well enough to publish it
  • try to calibrate the gas sensors better
  • take some readings in different environments
  • add a Wi-Fi switch so the system can operate without WiFi when desired

I have to be on the road over the next little while, so my project time will be severely limited, but we will see what can be managed...


All links to blogs related to this project can be found in the first blog here:

Safe and Sound - Invisible Hazardous Environmental Factors Monitoring System - blog 1