Transfering from template to fabric
The last couple of weeks I’ve been continuously working on the wiring of the displays. The first challenge was to prevent the naked wires touching the conductive fabric underneath. In the morning I had another brain wave: I should isolate the wires instead of the fabric. After talking to the salesman in my favourite electronics shop I went home happy because he showed me some nice silicon tubing and cables that I could use. The cable (with its contents removed) was still rather thick. I couldn’t iron it onto the displays. So I went for finer tubing which I could buy from my shop in a nice set with different sizes inside. This wasn’t enough by far so I ordered another five meter online which was only just enough…
I figured out the different amounts of resistance needed for the different ring diameters. The smallest rings now use very thin wire that has a resistance of 44 Ohm per meter. Rings 2 are a resistance of 10 Ohm. Rings 3, 4, 5 and 6 use the 6,9 Ohm wires that I started out with. The two biggest rings are 2,5 Ohm. This way I can keep the heating times together and not make them too long.
Attaching the wires
First I shaped the wires onto a paper template to determine the lengths needed. Then I isolated them and uncoated the end parts of the ones that had a lacquer coating. Then I embroidered the isolated wires onto ordinary fabric making sure that the connection parts were sticking out at the back. Connecting the resistive wire to the common wire using the terminal tubes was not as easy as I expected. It took quite a lot of squeezing and re-squeezing. I secured the connection parts with yarn to make sure they can take a certain amount of pulling. The whole strip of cables I secured with glue from a glue pistol.
The final bottle neck was the code. I’d been struggling with that for weeks. Mainly because the internal workings of the shift register remained unclear to me. I kept thinking that I needed to shift all the positions to get the outmost ring to light up, working with endless loop variations. I finally asked help from Marius again. He is a real hard- and software wizard. First he corrected my code by mail to make the outmost ring light up. It appeared I didn’t need a loop at all. He just pulled the byte values from the array…
As there were also some hardware problems he was kind enough to come over. He rewrote my software (that took me weeks) in 15 minutes! The code is now completely dynamic (and highly compact) using one big loop for all three displays.
We did some measuring and it appeared that the displays, when heating four or more rings on all three displays, use 10 Ampere which the batteries can’t really deliver. They should but they don’t. Which causes the voltage to drop. So I’m considering using a battery from an electric hand tool, a drill for example.
But for now I’m very happy with what I’ve got. It works and the concept is clear. I’m ready for the photo and video shoot upcoming weekend.
Displays in action
I’ve been working my ass of this weekend to get the displays working for the video shoot. I had to moderate my goals where the coding is concerned. I couldn’t get it to work the advanced way for three displays. So I chose just to light up an equal number of rings for every display, using the same amount of heating time for every three similar sized rings.
Wiring of the three displays inside the vest
Full of expectation I switched on all the batteries, pressed the demo button and… nothing. Not a thing happened. After some fiddling I got the smallest of one of the displays to heat up. Paul gave me some testing tips so I could test each ring separately. I got the two smallest rings of one display working. No matter what I tried the third or forth ring just wouldn’t light up. As it has become very cramped inside the vest with all the wires I asked my model, Hans, to help me on Sunday with the testing and we would do the video shoot later, when it was fixed.
The cooperation went very well. We tested and re-soldered some of the rings until we had the two smallest rings working for every display. But when it was time for Hans to wear the vest and press the demo button again nothing worked. We went back to just lighting one ring per display and after applying some pressure on the solder points three small rings light up feebly.
By then it was dark and I had to put up a very big lamp to light the room. With the utmost difficulty we got some reasonable shots. But alas the result is very poor.
The innermost ring of the NO2 display lighting up
Conclusion: this is not the way to go with the displays. These are the problems that have become clear:
- The soldered connection between the hard wire and the soft fabric isn’t stable. Often it doesn’t seem to provide enough power
- The fabric doesn’t conduct the power evenly. On some parts I can’t measure any current
- Often I do measure current everywhere but the fabric isn’t heated, *sigh*
- When turning on more rings the current seems to go the ring that is most conductive leaving the other rings with little or no power
- The more rings I try to heat the harder it gets to get even one working
Stepping into bed and removing my electric blanket I got a brain wave. Why not use this technology? I already had tips from Syuzi on this forum but I wanted to test my own set-up first.
After doing some research yesterday I’ve discovered there’re quite some producers of heated clothing. Some of the garments even work on 7 volt batteries. So that must be the way to go. Now I just need an electronics wizard to help me make the right choises.
I wasn’t feeling well but as I had so much to discuss I just had to go to last Saturdays’ workshop. A tailor was coming and Paul would also be there to help me build my shopping list so I could move on. My head was exploding with all the things that I was still uncertain about going through my mind.
I don’t know anything about tailoring or sewing so it was quite a relief to pose all my question to Michael. He had some nice solutions: I’ll make the fastenings asymmetrical so I can preserve the circles and I’ll sew a box to the outside of the vest where my sensors will be. It will give a nice sci-fi feel to it and it’s very practical because the sensors need fresh air anyway. He also cut a pattern so things are getting more concrete and (best of all) he’s going to make the vest :)
Diagram of Arduino architecture (Bluetooth is missing)
My meeting with Paul was also very calming for my brain. He immediately started drawing two nice schemes (called architecture), one for all the Arduino in and out pins and one for the power supply. Why didn’t I think of that… There are enough i/o pins on the Arduino to fit my project. I’m going to work with the Arduino Mini Pro and the BlueSMiRF Gold Bluetooth module.
As for the power we’ll need 7+ volts to power everything. So six AA batteries should suffice. All that’s needed is a set of amplifiers to boost the Ampere value for heating the conductive fabric. I’ll make a test with the largest circle so Paul has an indication and can start working on a design. These amplifiers should be placed as close a possible to the display to prevent energy loss.
Finally we’ll have to organize the sensor tangle and make it easy to plug in and out. I want to separate the display and the sensor part so I can wash the display if that’s needed.
Buttons, temperature and humidity sensor
On the photograph you can see the 5 volt circuit. It houses two sensors and two buttons. At the workshop last Saturday I put together button circuit, if you press the white one it means it smells good, the brown one indicates it smells bad. This is of course just a functional setup, purely for testing hardware and code. Later I’ll make soft buttons which will be integrated in the vest. We also made the humidity sensor (the kinky copper plate, we ran out of circuit board.) It will take some time to calculate the actual humidity from the output and before I can use it with the ozone sensor. A period of extensive callibration is due anyway.
I worked on the code which I completed today. The Arduino now collects data from all sensors (except the gas sensors which somehow have stopped working at the moment) and outputs an ‘e’ when no buttons was pressed, a ‘+’ when the smells good button was pressed and a ‘-’ when the bad button was pressed. It works in a two minute loop which is broken when a button is pressed, then data is immediately collected and send.
As for the sending part, I’m still working on the Bluetooth connection between the Arduino and the phone.
Nice vest with functionality
My aim for this workshop (19-9-09) was to put the three sensors together but we also had a have a meeting with AnnaMariaCornelia concerning the design. The rest was kind enough to let me meet first. I showed the various designs I did with the safety vest as basis. The vest was present from the start of this project because of it’s connection with safety and the clean way it signals a simple message. So Anna suggested I stick to those basics instead of just decorating the vest. She’s absolutely right of course. I should just use the esthetics and functionally of the vest to inform about air quality. Research has shown that the amount and broadness of the reflective stripes indicate higher safety. So I can vary the width of the strips to indicate more or less pollution, resulting in more or less visibility. I’ll use strips of conductive fabric to heat the paint. That should give a nice, clean result.
My research also showed that there are some very functional coats with different pockets. I want to use them in my design to store and build in the boards, buttons, phone and power supply.
The building of the board with sensors went pretty smoothly. That’s no surprise with an expert like Paul standing by my side. So now I’ve got a great little board with all the sensors powered at their own voltage. We also build in a switch to turn all the sensors on and off at the same time to increase their lifetime. We did discover that the ozone sensor is influenced by humidity. So I ordered a humidity sensor yesterday so I can at least measure it. How to interpret the data is a completely different question, the next problem to tackle.
Three sensors integrated into one board
It was four weeks since the last workshop. Despite of the time span I didn’t have a lot of time to spend on the project but I was content with the research I’d done and was keen to show my findings to Anna Maria Cornelia. I also hoped to get at least one gas sensor working.
As I had to wait before I could talk to her I started with Paul to work on the sensors. But first I had to reduce the voltage level for the NO2 and CO sensors to work. It took me an hour and a half to put it together (with help from Paul and Meg), hmm, electronics isn’t really my thing I fear. I find it very hard to translate a scheme (even a simple one) into a circuit. But it’s very nice to have help close at hand, maybe I’ll learn some day…
Then it was time for me to talk to Anna Maria. I showed her the experiments and she was very exited about them and said they offered me a good springboard to continue. She said the parameters: colour, length, applied pressure and pressure duration are very usable for visualization.
The research will follow tree lines. Working with a roll of paper and ink plotted in lines and stains. A humidity meter which they have in museums is a good starting point. I also want to look into punching creating a relief, much like Braille. I could work on paper but also materials like latex rubber that can have a changing relief. This way you can feel the pollution, which is also nice at night. A matrix printer springs to mind to achieve this effect. The nice thing of working with paper is that you have a tangible result at the end of the day. Like an air quality receipt. Still I also want to send life data to internet and I’ll have to think about relation between these two.
Anna Maria suggested that I might use a screen to visualize digitally created flocks and maybe incorporate a watch so you only have to wear on thing around your wrist. She also suggested that it might be nice to somehow keep the functionality I’d used in the experiments working with smell to determine air quality. I could send a marker when I notice something about the air quality so I can later see them side by side to see if my intuitions were right.
She wants me to make five (!) different prototypes by September that translate the manual experiments into something mechanical and digital.
Back with Paul I managed to get the CO sensor working. That is, it outputs a voltage which varies when I breath or blow on it. The NO2 works exactly the same so it shouldn’t be to difficult to build. Now I have to find out what a certain voltage level means. But I will have to make a start in sending the data to a server. The next two months will be very busy…
On Friday 25/07/08 Richard and I have worked on the sensor. The makeshift one was too unstable to give reliable results. We used Barbara’s felt prototype as a starting point. It soon became clear that the stiff wires we used didn’t go well with the soft felt. It’s hard to wear the sensor around the finger and keep it light tight. I think it also is too big for me. But it worked in the sense that it generates data. The tiny LED gives a lot of light :) So the concept works but the realisation needs some fine-tuning.
So we’ll have to look for more solid material on the one hand and less stiff wiring on the other to make the sensor fit tightly and nicely. Materials the could be used are leather, rubber or neoprene (diving suits). I know someone who can sew these thicker materials. I’ll ask her to help with a prototype.