Automatic Resistance: Resistors Controlled by the Environment

Resistors are one of the fundamental components used in electronic circuits. They do one thing: resist the flow of electrical current. There is more than one way to skin a cat, and there is more than one way for a resistor to work. In previous articles I talked about fixed value resistors as well as variable resistors.

There is one other major group of variable resistors which I didn’t get into: resistors which change value without human intervention. These change by environmental means: temperature, voltage, light, magnetic fields and physical strain. They’re commonly used for automation and without them our lives would be very different.

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Resistance in Motion: What You Should Know About Variable Resistors

Adjusting the volume dial on a sound system, sensing your finger position on a touch screen, and knowing when someone’s in the car are just a few examples of where you encounter variable resistors in everyday life. The ability to change resistance means the ability to interact, and that’s why variable resistance devices are found in so many things.

The principles are the same, but there are so many ways to split a volt. Let’s take a look at what goes into rotary pots, rheostats, membrane potentiometers, resistive touchscreens, force sensitive resistors, as well as flex and stretch sensors.

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Interfacing with an analog joystick

[Firestorm_x1] put together a tutorial about interfacing an analog joystick with a microcontroller. These analog sticks are easy to find; he got his from Goodwill but we’ve got a couple in our junk box right now. The stick uses variable resistors to report its position so it’s just a matter of reading and interpreting that data. After explaining the concepts he demonstrates how to use the joystick to control a Basic Stamp 2 based robot, the Boe-Bot. This could easily be adapted for use with other robot platforms.