A technical meeting

There was a small group at the meeting last week. Which was nice in the sense that we could all claim Paul (the engineer) for a longer time. Today we all inventoried our current status and needs with regard to the technical part of our projects.

Thermochromic ink

Testing with conductive yarn and thermochromic ink
Testing with conductive yarn and thermochromic ink

First I did tests with the thermochromic ink and conductive yarn: to change colour the voltage should be between 6 and 12 and 0,1 ampere. With 6 volt you can change ink above a straight line of yarn for about 6 cm. For longer stretches stitching of the same length can be placed parallel. When the yarn is stitched tightly it is easier to change the colour. Thickness of yarn will make a difference. I’ll have to do some tests. I can use an adaptor to try out different voltages to work with, the ampere value can stay the same.
I worked a little on the Arduino program which will be pretty straight forward. I will have to make sure that the sensors have time to heat up before I read the data. It is unclear how many minutes the sensors may stay on. They may deteriorate quickly when they stay turned on too long.
Paul is going to work on the schematic for the three analogue sensors. It’s pretty complicated because they use different voltages. We’ll be using a part that will allow us to completely switch them off. It will give us more control and save power. He’ll also calculate the power needed. Most power will go to heating the yarn or wire for changing the colour pattern. Depending on the length of the wires we’ll need more or less power.
Solar power
It is possible to realize the wearable using solar power. The panels will be used to charge batteries and not to power the wearable real-time. Solar power is too instable because I’ll be needing enough power every two minutes to measure and change the display. But it will run independently on it’s own solar panels which makes me very happy. I’ll probably need 6 C batteries to power the wearable which will make it heavy…
I’ll probably use Bluetooth to communication for talking from the Arduino to the phone. As I can’t find any documentation on serial/USB communication.

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