OSPb - An Open Source Lead Tester

Today was payday, so another order off to Sparkfun. I ordered an I2C light sensor breakout and some assorted prototyping parts that I *should* have had around (e.g. breadboard) but seemingly have vanished. Oh well. Nothing wrong with having an extra breadboard or two. I hope to have some real progress updates soon.

Well this is interesting. I overlooked the fact that the Pi does not have analog in, so a simple photodiode like the I've procured needs a RLC circuit or ADC to work. A quick google search that there are libraries for the RPi to so some image processing using a webcam. Hmm...a webcam measuring incident light rather than a pin diode. Decisions decisions....

I started laying things out in Eagle whilst I wait for parts to arrive from Sparkfun. Mainly this has been limited to recreating what I found in the above video. Here is a rough shot without the RGB diode connected to the GPIO pins, which is an easy fix.

I also made a mockup of the device next to an Iphone 6 for size comparison. This makes me think I really need to find a way to cut down on the height of the module. I likely can cut the height to just above the Pi's USB ports. Doesn't need to be much higher than that methinks.

I found a great Youtube video showing you to control an RGB LED. I'll post here for reference, as well as throw it in my Trello scrum board for this project.

So today I fired off my first order to Sparkfun. Instead of choosing a single color (i.e wavelength) LED I ordered their WS2812 LED breakout board. Along with a 'solar cell' that doubles as a pin diode. If I have to splurge on a 'reall photodiode I will, but I would prefer to save the money.

I also started tweaking the CAD model a bit. The idea is to bounce the LED light off a test strip and capture the reflected light using the pin diode. We would calibrate the test strip measurements to known samples from a local municipal lab that I have a relationship with.

So we all know about Flint. Lead in the water. Sick children. The greed, and the blind eye. So let's take that problem and seek out solutions. One way solution I can think of is to 'democratize' accurate water testing. Sure, you can go buy lead water test kits at Walmart that use test strips, but genuine photometer-based tests can be prohibitively expensive.

So let's learn how the expensive tests are done, how those devices work, and see if we can do it on a much less expensive scale using off-the hardware, and maybe...just maybe...those test strips.