I wanted to bridge the gap between what for me had been an enclosed capsule of capturing / visualizing my own physiological data and entwining it with data from the environment around me. The barometric skirt visualises data from four sensors, three of them are environmental: temperature, pressure and altitude, the forth is a temperature sensor that sits on the inside of the skirt and pulls in my body temperature. I’m interested in how I can display my physical data alongside that of the ‘bigger picture’ of elements that I am surrounded by.
If you haven’t seen or heard of a barometric sensor board before, it’s a PCB (Printed Circuit Board) and the BMP085 I’ve used integrates temperature, atmospheric pressure and altitude sensors, these together constitute a suite of sensors that can be used for looking at weather data. You may have heard of ‘pressure’ attributed to weather terms such as high or low pressure – high pressure generally relates to warm, sunny weather and low pressure colder, wetter weather. Sensors in a barometric board are also used in altimetry to measure one’s present altitude, or for example, how high one has climbed.
I decided that I had to make a bespoke skirt for this project due to the way I wanted the RGB LED strip to display from inside the skirt. It took me a while to find a skirt pattern that I thought would suit the project, I’ve gone for an A-line skirt with a dropped waist, which I thought would support the components quite well, especially as RGB LED strip requires a 12 Volt supply, which isn’t exactly light! My initial idea was to make a jolly big pocket for the battery pack, but after spending a day experimenting with pocket making, I decided to make a Velcro on-and-offable components substrate apron (for want of a better term) which goes in the middle of the skirt fabric and lining layer, I made a fitted pocket on the substrate apron to hold the 12V battery pack.
The skirt required an illustration to enhance the component design and after pondering weather icons and scenes I decided that I wanted a Japanese feel and practiced fabric painting on with calligraphy brushes and tested various fabrics for holding paint, washability, shrinking and ironing capabilities. In the end I chose to create some Okami style weather designs inspired by the beautiful characters and fan art, so after making 2 or three prototype skirts in satin and organza (and being driven half mad by this task) I painted weather bound characters directly onto the skirt.
Having got the skirt (with the lining to shield the wearer from electronics components) mostly made, I moved on to the electronics. This took some of thinking about as I wanted to visualise data outputted from four sensors individually via RGB LED strip, the resulting rats nest took up three breadboards and contained so many components and wires it would have been a nightmare to reproduce and solder onto stripboard. Luckily a way to consolidate this somewhat came with the introduction of two array ICs. I added another temperature sensor to the circuit for measuring my own temperature and the whole lot was driven by a Shrimp kit instead of my usual choice of microcontroller board such as a LilyPad Arduino. “The Shrimp” as explained on the Shrimping It website is “a Arduino-compatible, handmade circuit you can use to create your own digital inventions” – basically it’s a low cost kit of components that you can put together yourself on breadboard or stripboard. This saved me a lot of space as I crammed all my components (bar the barometric sensor I wanted on the outside of the skirt and 12V battery pack) onto one piece of stripboard.
I’ve written the code, or sketch in C, with the inclusion of the Wiring library and the example code library for the BMP085 which does all the complex and clever calculations to convert readings to °C (Celcius), Pa (Pascal) and m (meter) readings. If you’ve got the barometric sensor set up using the Arduino IDE you can open the serial monitor to see the readings fly by.
I spent the next two weeks stripping wire and soldering, I also did a lot of desoldering and resoldering as I endeavoured to get the shrunken, but still a rats nest of wires in the correct groupings of PWM (Pulse Width Modulation) and digital input and output to their respective pins to match up with my code. I can’t underestimate the value of double checking wires and tracks before soldering, though it’s incredibly easy to make mistakes as wiring is always fiddly and tracks are so close together. Also, don’t forget to work out where your track cutting should be before squeezing everything into a small piece of stripboard – always leave an extra line or two in tracks for contingency! If you’re using a coin cell battery, it’s a good idea to get a small, solderable holder for it, but be selective in which type you choose as some are much more fiddly to release the battery than others! I should also mention that I couldn’t find a stripboard friendly version of a 2.1 barrel socket for the 12V battery pack, so I used an SMD one, but had to dig into the stripboard to join two track holes together. Another top tip is try to get a track in between your 12V and ground tracks, just in case of any stray solder bridging!
Before sewing the stripboard and RGB LED strip to the apron substrate, I added some strong Velcro to hold the apron to the skirt lining fabric, next time I do this style of embedded electronics I will use a stronger substrate for the electronics as lining fabric isn’t really robust enough for suspended 12V battery packs! Until I do a better photo shoot / video enjoy some the photos and video I’ve made along the way.