The resistance of a relaxed stretch sensor is about 3.5K ohm. When stretched, the resistance may increase to about 14K ohm. But take comfort into consideration. The sensor can not be used in a tightened way. So the resistance should be 3.5K~4K in design.
In order to make it easier to use, I used a dandelion module instead of an Arduino. The dandelion board is designed by me one year ago and can be powered with a Li-poly battery or 5V source which makes it portable and compact. It communicates with other devices through virtual serial port on Bluetooth. So I can use processing to send commands to control its IO ports and read values from them.
The ADC in dandelion uses a 1.8V reference. So I chose a 1.1K resistor off my hand. In this case the voltage on the analog pin should be less than 3.3*1.1/(3.5+1.1)=0.79V. When the sensor is stretched, the resistance will increase which result in the decreasing of the ADC value.
In order to fix the sensor on my chest, I used wrapping-wire. Each hook is warped with a piece of uncoated wire. Since the wire has an insulating coat and has a little rigidity, I can twist the wire at a desired point and from a small loop, and hood the sensor on. In this way I can adjust the length of the loop easily.
After wrapping the system on my chest, the value will drop when I breathe in. Also the log recording function works well.
When talking to how to increase happiness. The reading materials show 3 levels of ways:
The lowest level is doing things that make us happy. This includes leisure, making friends, etc. These methods are easy to achieve, but happiness is hard to sustain. So it is only suit for short term happiness.
The medium level is to create a flow. If we focus on some challenge that can absorb us, we won’t have enough energy for ourselves. In this case, we may not notice the change of time, the statues of ourselves. This statue of ecstasy will bring more happiness.
The highest level is to fill our lives and make them meaningful. If there is a life long career that makes our live more valuable, especially for others, we will feel a long lasting happiness.
