Potential Divider Applications (LDRs and other sensors)
Voltage dividers have tons of applications, they are among the most common of circuits electrical engineers use. Here are just a few of the many places you’ll find voltage dividers.
Potentiometers A potentiometer is a variable resistor which can be used to create an adjustable voltage divider. Internal to the pot is a single resistor and a wiper, which cuts the resistor in two and moves to adjust the ratio between both halves. Externally there are usually three pins: two pins connect to each end of the resistor, while the third connects to the pot’s wiper. If the outside pins connect to a voltage source (one to ground, the other to Vin), the output (Vout at the middle pin will mimic a voltage divider. Turn the pot all the way in one direction, and the voltage may be zero; turned to the other side the output voltage approaches the input; a wiper in the middle position means the output voltage will be half of the input. Potentiometers come in a variety of packages, and have many applications of their own. They may be used to create a reference voltage, adjust radio stations, measure position on a joystick, or in tons of other applications which require a variable input voltage. |
Reading Resistive Sensors
Many sensors in the real world are simple resistive devices. A photocell (LDR) is a variable resistor, which produces a resistance proportional to the amount of light it senses. Other devices like flex sensors, force-sensitive resistors and thermistors, are also variable resistors. It turns out voltage is really easy for microcontrollers (those with analog-to-digital converters - ADC’s - at least) to measure. Resistance? Not so much. But, by adding another resistor to the resistive sensors, we can create a voltage divider. Once the output of the voltage divider is known, we can go back and calculate the resistance of the sensor. https://learn.sparkfun.com/tutorials/voltage-dividers |