Ups and downs

measuring electricity

Paul explaines how to measure the power used for the heating of the fabric

I’m having a hard time with my wearable. There are different areas where I’m experiencing problems:
- The thermochromic ink deteriorates very fast. Under influence of UV radiation for which I haven’t been able to find a solution. The amount of electricity it needs to heat up is very much depending on the air temperature. Also the width of the strip of fabric (this has to be equal for the whole length) is crucial for successful colour change. So there’s a lot of testing ahead before this will work well. I have switched from reflective strip to using reflective fabric, I wonder if the performance will improve.


Arduino talking to Nokia

- I’ve been talking to a lot of experts lately but Friday last I got a pretty disturbing e-mail from the RIVM which is a leading Dutch centre of expertise and research, it advises and supports policy-makers and professionals in public health and environmental areas. The gases I’m measuring are a good indication of air quality but the sensors I’m using aren’t sensitive enough. I was happy to find gas sensors in the first place but now they appear to be worthless for my purpose.
- Programming the Bluetooth connection has made some progress. I can now connect with the Arduino board and send and receive bytes. Now I’m at the final stage of sending all of my sensor data in a single string to the Nokia. I also have to find out how to let Python check for incoming serial data continuously. Some sort of event listener.
- I keep having trouble using the internal GPS. It seems to break down after I’ve used it once. Only a restart will make it work again.
- On the bright side I’ve made two dummies for my vest. Saturday I worked together with my tailor on my second dummy, using the actual fabric. This gave me a lot of insight in what I want. Discussing it with AnnaMariaCornelia it became clear that I have to take a radical turn to make my vest look like true work ware. I’m really looking forward to designing my vest and make it look sturdy and cool to wear.


The second dummy which at this stage looks too much like an apron

Python kick-off

Last week I did some research on Python for mobile devices. I was so enthusiastic about the documentation I found online and the apparent ease of the language that it was also clear to me what Smartphone I would buy. After quite some hesitation I decided to go for the Symbian based Nokia N97. It beat the i-Phone because I’m already used to Nokia, it has a real keyboard, a 5 mega pixel camera and it runs on Symbian. I found this great tutorial by one of the authors of ‘Mobile Python: Rapid prototyping of applications on the mobile platform.’ I haven’t bought it yet. I’ll see how far I can get without it as there is lots of info to be found online. They do have a chapter on interfacing with an Arduino board which isn’t in the code section. To get started you only need a simple text editor and the latest stable Python for S60 (Pys60) programs which you must upload to your phone. At this moment they are the Python_1.9.4.sis and PythonScriptShell_1.9.4_5thEd.sis as my phone runs on the latest, 5th edition of Symbian. They are not at the top of the maemo list so it took me a while to find out which versions I had to download. I installed them with my Nokia software. All I had to do was to write a little script:

import appuifw
appuifw.note(u"This works", "info")

For example and store it as a .py file. Upload it to my phone. Then go to the Pys60 program on my phone, run the script and see the following astonishing result ;-)

It works!

It works!

Even though the result is of course very simple a ‘Hello World’ script is quite rewarding because you know the routine of writing and uploading and you know your software is working correctly. I’m really looking forward to programming scripts on my phone because so much is possible. From databases to turning your phone into a server!