Tribe Against Machine Wiki | e-Textile basics

分壓電路 Voltage divider

Arduino的類比輸入腳位（analog in）讀取的是電壓，而不是電阻。當您要使用電阻式感應器時（像我們課堂上的碳煙壓力感測），您需要進行電阻式改變來控制從感應器進入Arduino類比輸入腳位的電壓。為了這個目的，我們可以製作一個分壓電路。您可以使用2個電阻「分壓」。如第一個圖表所示，比如說您有2個完全相同的電阻，則電壓會被分為一半一半。隨著兩個電阻之間的比例，您獲得的電壓比例也會相應變化。

可以這樣計算
電源電壓（5v）x電阻A /（電阻A +電阻B）= 分壓
Here's the translation of the description about voltage divider on Kobakant:
''Arduino‘s analog pins are reading the voltage that comes in, not the resistance over the two points. When you want to use a resistive sensor (i.e. neoprene bend sensor), you need to manipulate the voltage that goes into the analog pins with the resistive change the sensor makes. For this, we can make a voltage divider circuit. You can divide the voltage by using 2 resisters. If you have 2 exactly same resistors, the voltage gets half in the middle, like the first diagram. As the ratio between two resisters changes, the voltage you get in the middle (between the resisters) changes accordingly.
One can calculate this by Supply voltage (5v) x resistanceA / (resistanceA + resistanceB) = divided voltage''

explanation of voltage divider

simple pressure sensor

1. first soldering! we soldered a karl grim thread, a Dupont DIP pin and 2 square of EMI tape sheet together.
2. cut off a velostat sheet with the same size (but a little bit bigger than the EMI) and sandwitch it in middle of the two EMI sheets, your simple pressure sensor is done!
3. connect the pressure sensor to voltage divider and upload the arduino code. in this case we use the pressure value as the blinking gap of the LED.

pressure sensor matrix
We followed the tutorial of Hannah's pressure sensor matrix (check the reference), turning the one node pressure sensor to matrix. Here was our version:

firstly solder the 28 DIP pins for every pinouts of teency lc. (14 pins each side)

cut 7 stripes of EMI tape and then stick it to two pieces of non-conductive fabric sheet. We soldered 14 enameled wires to 14 EMI tapes. Finally we sand witch it with the velostat sheet like the pressure sensor we made before.