PurpleAir Sensor Investigation and Teardown, Pt1

With the ongoing poor air quality all over Central California due to the Camp Fire, the interest of providing fine grained and reliable air pollution measurements peaked. One of the interesting providers of data is the website PurpleAir.com. The data for PurpleAir is sourced from a series of sensors sold through the website

Parts Roundup: FemtoFET

FemtoFET vs SOT-23

Ever felt like your board level MOSFETs were too large?

Texas Instruments now has an answer!

Simple CO2 Solenoid Carbon Doser Project

Controlling pressurized carbon dioxide (CO2) delivery into a Calcium reactor or into a planted tank with precision can be fraught with problems. The conventional mechanism is to use a needle valve after a pressure regulator - this design is very finicky to adjust for low flow rates and has a tendency to drift over time, meaning your carefully controlled delivery is now out of whack. In addition, if you use a pH controller driving an AC solenoid valve, the valve actuation can be quite audible.

Spectrometer Pt 2 - Driving

First things first, we need to figure out how to drive and read the spectrometer. There are two key diagrams to consult - the suggested application and the timing diagram. The application diagram shows several key signals, some of which the meaning isn’t clear at first. After reading through the rest of datasheet, you can generally make out the following pins: Video - the spectrometer is like a 2d camera - it is an image sensor in a line after all.

Spectrometer for LED lighting analysis

Hi! You may remember me from other threads like LEDBrick DIY puck and high density stars, plus drivers (now available on blueAcro.com and the Apogee sensor PAR interface board. Many moons (months) ago, I dropped some money into a GroupGets buy for a pair of Hamamatsu Micro-spectrometers. They can resolve light intensity between 340-780nm in up to 15nm increments. They are not cheap ($180 on groupgets, qty1), but are a lot cheaper than other commercial pre-packaged light spectrum units that employ an actual spectrometer (and not a coarse approximation using an RGB light sensor).

Design Log: LEDBrick Acrylic Enclosure

I spent some time mocking up a case for the lights. I’m not totally happy with the side panels yet (more on that later), but a quick walk through the process:

Design Log: LEDBrick - part 2

Nearly 6 months later, and after back-burnering the project multiple times, I’ve made some significant progress on the LEDBrick aquarium light. In the space between blog posts, I’ve: Received a round of metal-core PCBs for the LEDs. Designed an 8 channel driver board based on the L3414, a different sketch from the original planning Machined a single heat sink, and did test mounting of the emitter board. Populated one emitter board.

Design Log: LEDBrick Aquarium LED Lighting

This design has been on my back-burner for quite awhile, but its time to write it up and continue pressing on.

I really like reef aquariums. I currently have a (modest) 90 gallon system, which has livestock dating back to when I started keeping salt-water systems in college (circa 2004). How I managed to actually afford keeping a salt-water system in college is beyond me, but things have progressed nicely.

Design Log: NixieView

As part of an effort to share more designs, I’ve decided to start writing a continuing series of blog articles on my hardware design efforts. This first article covers the NixieBoost of a NixieView.