The voltage divider also known as the Potential Divider, is a very common simple circuit which is used to change a large voltage into a small voltage. Through this article, you will learn everything about voltage dividers like:

  • What is a Voltage Divider?
  • Voltage Divider Circuit
  • Voltage Divider Equation / Formula
  • Examples of Voltage Dividers

What is a Voltage Divider?

  • Passive Linear Circuit that produces output voltage that is a fraction of its input voltage.
  • It scales down input voltage to a smaller voltage based on the ratio of the 2 resistors through distributing input voltage among components of the divider.
  • Often used to supply a voltage different from an available battery or power supply.
  • Output voltage of voltage divider is dependent on the resistance of the incoming load.

Voltage Divider Circuit

A voltage divider circuit will normally look like this in a circuit with a series of 2 resistors.

  • R1 = Resistor closest to input voltage (Vin)
  • R2 = Resistor closest to ground
  • Vin= Input Voltage
  • Vout = Output voltage across R2 which is the divided voltage (1/4 of input voltage)

Voltage Divider Formula / Equation

Equation to find the output voltage of a Divider Circuit:

R2 / R1 + R2 = Ratio determines scale factor of scaled down voltage.

For example,
Vin = 100, R1= 20, R2= 10

With the help of a calculator you should get:

Voltage Divider Rule

  • The voltage division rule states that: The voltage divided between two series resistors, are in direct proportion to their resistance
  • Which means your circuit can have more than 2 resistors!
  • Voltage Divider Rule Formula:

Example of Voltage Divider Rule Equation:

Ohm’s Law

Now, we can use Ohm’s Law to calculate the voltage flowing through each resistor:

  • Equation for Ohm’s Law = E = IR
    • E = Current across each resistor
    • I = Circuit Current
    • R = Resistance
Ohm Law
R1R2R3Total
E (Volts)5101530
I (Amps)2.5m2.52.5m2.5m
R (Ohms)2K4K6K12K

Thus, the current across each resistor is 5V, 10V and 15V respectively!

Simplified Equations

  • If R1 = R2,

  • If you are solving for R1,

  • If you are solving for R2,

Examples / Applications of Voltage Dividers

Here at Seeed, we offer many various types of Voltage Dividers. Here are the different types of Voltage dividers that we offer:

Grove – Slide Potentiometer


  • Most voltage divider circuits involves a potentiometer which is a variable resistor.
  • How does it work?
    • The manual wiper which is movable, touches a resistive strip of material. When it is moved up closer to terminal 1 and away from terminal 2, resistance is lowered to terminal 1 while resistance is raised at terminal 2 and vice versa.
  • The potentiometer is useful to help achieve a variable voltage from a fixed-voltage source. It can connect the outer terminals of a potentiometer across the voltage source and control the voltage you need between your potentiometer and one of the outer terminals for your circuit.
  • The Grove – Slide Potentiometer incorporates a linear variable resistor with a maximum resistance of 10KΩ. As the slider moves, the output voltage will range from 0 V to the Vcc you apply.
  • It connects to other Grove modules through a standard 4-pin Grove Cable.
  • Below is an image of the Potentiometer schematic diagram:
  • It has many purposes like being an Adjustable Resistor, standalone, voltage divider with Arduino or even as a human interface device (HID) which means it can be used to control a car!
  • Some projects you can do with the Grove – Slide Potentiometer  are like making your very own Beatbox or Boombox with Arduino!

Grove – Voltage Divider

  • The Grove – Voltage Divider provides an interface for measuring external voltage which eliminates the need to connect a resistance to input interface
  • With a dial switch, you can easily select the voltage gain which makes it simple to use.

Grove – Rotary Angle Sensor(P)

  • The Grove – Rotary Angle Sensor(P) is also another potentiometer.
  • It is capable of producing analog output between 0 and Vcc (5V DC with Seeeduino) on its D1 connector.
  • With a resistance value at 10k Ohms, it is perfect for Arduino use.
  • It is supported on all MCU platforms like Arduino, Raspberry Pi, BeagleBone, Wio and also LinkIt ONE.
  • One of the projects that you can do with this potentiometer is using it to control your LEDs brightness
Using Arduino to control the brightness of an LED through Grove-Rotary Angle Sensor(P)

Resistive Sensors Reading

  • Most sensors are simple resistive devices like our Grove – Infrared Reflective Sensor. However, most of them are only able to read voltage but not resistance.
  • By adding another resistor to the circuit, we are able to create a voltage divider together with the sensor.
  • As we are able to check the output of the voltage divider, we can now calculate the amount of resistance of the sensor.
  • An example of the circuit is as shown below where R2 is a resistive sensor:
  • For example, the resistive sensor is a Grove – Temperature Sensor which is a thermistor with a room temperature resistance of 350 Ω where the resistance of R1 is fixed at 350 Ω
  • Using the Voltage Divider Equation:

TemperatureVin (Fixed) R2R1 R2 /
(R1+R2)
Vout
Cold5V300 Ω
350 Ω0.462.3V
Room Temperature5V350 Ω350 Ω0.52.5V
Hot5V400 Ω350 Ω0.532.65V

Level Shifters

  • What happens when a sensor and a microcontroller with two different voltage meets? Without the voltage leveled down, for example, directly interfacing a 5V logic output microcontroller to a 3.3V input sensor can cause damage to your 3.3V circuit.
  • This is where the hero: A voltage divider comes in and saves the day acting as a level shifter which interfaces two circuits that use different operating voltages.
  • The voltage divider can help level the voltage down from a microcontroller (eg. 5V to 3.3V) to avoid damage to the sensor which makes it safe for the sensor to handle.
  • Do take note that the voltage divider can only work in one direction: level down voltages but not leveling up.
  • Here is a table of resistor combinations for leveling down commonly encountered voltages:
Resistor CombinationVoltages to be leveled down
4.7 kΩ and 3.9 kΩ9V to 5V
3.6 kΩ and 9.1 kΩ12V to 3.3V
3.3 kΩ and 5.7 kΩ9V to 3.3V
  • Do note that it is not recommended using a voltage divider to level down a large load like 12V to 5V as they are not meant to supply such power to a load as with such a load, it may melt the resistor. (You can use voltage regulators instead like our Adjustable DC&DC Power Converter (1.25V – 35V&3A)

Summary

With all the knowledge of Voltage Divider in your hands, you are able to turn any voltage into a smaller one like a magician! Want to test your skills by making your very own Voltage Divider project? Here are some project ideas to get you started using a potentiometer and an Arduino to create a beatbox or a boombox on our wiki page: Grove – Slide Potentiometer Wiki

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