EarthWearth: Lulu Wein, Matthew Siegel, Ron Wolf, and Marci Brustman
Weight Measurement – Load Cell, Force-Sensitive Resistor
The load cell is a small metal bar that is designed to convert the forces placed on it into electrical signals, which can be measured by a computer like the Arduino. Basically, it measures weight. It does this, using variable resistors on both sides of the cell, which measure tension and compression. The signals from these resistors are sent through an operational amplifier (described below) and read by the Arduino.
A transistor is an electronic gate, which allows current to flow through it given the correct input. Transistors are needed to help power electronic components which need more than the 5 volts from the Arduino, by acting as a switch. (They can also be used to amplify voltage or current, but this article will talk about the switch function.) There are two types of transistors, NPN and PNP, which accomplish the same goal, but through different methods.