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 about:
- What is a Voltage Divider?
- Voltage Divider Circuits
- Voltage Divider Equation / Formula
- Applications 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.
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:
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
Thus, the current across each resistor is 5V, 10V and 15V respectively!
- If R1 = R2,
- If you are solving for R1,
- If you are solving for R2,
Applications of Voltage Dividers
Voltage dividers circuits are very common and are found in many applications. Here are a few examples of where a Voltage Divider circuit is found:
- A potentiometer is passive electronic component with a sliding or rotating function that acts as an adjustable voltage divider.
- The voltage input is applied across the entire length of the Potentiometer and output voltage (voltage drop) is controlled with the fixed and sliding contact of the potentiometer.
- There are two types of Potentiometer
- Rotary Potentiometers (Rotary Knob)
- Linear Potentiometer (Slider)
- Here at Seeed, we offer both types!
- 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!
- The Grove-Rotary Angle Sensor (P) 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
- Interested? You can check out the projects ideas here and also for more detailed information on our wiki page: Grove – Rotary Angle Sensor Wiki
- Want to know more about Potentiometer Functions, types, etc? Check out our other blog about Potentiometer – Functions, Types and Applications!
- 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.
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:
|Temperature||Vin (Fixed)||R2||R1||R2 /|
|Cold||5V||300 Ω||350 Ω||0.46||2.3V|
|Room Temperature||5V||350 Ω||350 Ω||0.5||2.5V|
|Hot||5V||400 Ω||350 Ω||0.53||2.65V|
- 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 Combination||Voltages to be leveled down|
|4.7 kΩ and 3.9 kΩ||9V to 5V|
|3.6 kΩ and 9.1 kΩ||12V to 3.3V|
|3.3 kΩ and 5.7 kΩ||9V 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)
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