If you have a traditional regulated power supply that you want to make adjustable, you’ll have somewhere in the circuit a feedback line driven by a potential divider across the output. That divider will probably incorporate a variable resistor, which you’ll adjust to select your desired voltage.
The problem with using a standard pot to adjust something like a power supply is that a large voltage range is spread across a relatively small angle. The tiniest movement of the shaft results in too large a voltage change for real fine-tuning, so clearly a better means of adjustment is called for. And in many cases that need is satisfied with a ten-turn potentiometer, simply a pot with a 10 to 1 reduction drive built-in.
[Dardo] had just this problem, and since 10-turn pots are expensive to buy and expensive to ship to his part of the world he built his own instead of buying one.
Continue reading “A Ten Turn Pot, For Not A Lot”
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.
Continue reading “Automatic Resistance: Resistors Controlled by the Environment”
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.
Continue reading “Resistance in Motion: What You Should Know About Variable Resistors”
[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.