I have been in Washington making a technical presentation in an unbelievably secure building, but now I'm back and it is time to catch up.

I am still waiting for some parts for my sensor card – it is starting to look like I will have to kludge some connectors and use lower performance amplifiers to get it working within the schedule. In the mean time I am using the working parts of the system to take some readings in my environment and I'm also doing a lot of 3D design and printing to make all the modules wearable.

Rather than try to build suspense, here is a short video showing three wearable instruments on one arm:

The concept is to mount all these devices on my forearm where the displays can easily be viewed and the controls can be easily accessed. This arrangement keeps both hands free for other tasks and eliminates the need to carry a tool box and set it down when taking readings. I am experimenting with different friction in the hinges - it is nice to be able to flip the displays up or down just by twitching my arm, but inadvertent flipping may be too big of a drawback.

The two flip-up modules have five 3D printed pieces each, plus a stretchy strap and some fasteners. The meters have some foam rubber in the caps so that when they are cinched down, everything remains snug with no rattling. The meter caps are held down with wire-ties, which minimizes the complexity and size of the 3D cases, while providing a very secure, snug fit. (obviously designed by an electronics guy) The Wi-Fi enabled gas sensor display uses seven 3D printed parts – covered in an earlier blog. Considering these modules are first prototypes, I am very happy they work so well.

There is still one module not shown – the multi-gas sensor - although most of the electronics are shown working in an earlier blog. Some of the 3D printed parts are finished, but at least one section is not designed and the cards cannot be stacked yet to finalize measurements for it.

In a previous blog a discussion came up about the use of (radioactive) Americium in smoke detectors so here is a follow up with some tests.

Here is a picture of what my radiation meter reads when next to a smoke detector in my house:


Here is a picture of the background radiation in my house:


The meter is pretty nice in that it provides an accuracy estimate as well as a reading. The accuracy in these readings is no better than 40% because the meter was not running very long and the amount of radiation is very low. Which means these readings could be the same real value although the smoke alarm area was consistently very slightly higher than other areas. Whatever radiation is reaching the meter is probably gamma radiation as I don't see how alpha particles could reach the meter with any velocity. My conclusion is that any radiation from the smoke detector is pretty similar to background radiation and generally the background radiation will be larger than any contribution from a smoke detector.

My next blog will be a discussion of microwave hazards including cell phones and some readings from my environment. After that I will be working on gas sensor software while waiting for parts to arrive.


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