Voltage Divider Calculator
What is a Voltage Divider?
A voltage divider is a series arrangement of resistors that converts a higher voltage to a lower voltage. The output voltage depends on the ratio of the resistors used in the circuit.
How Does a Voltage Divider Work?
A voltage divider works by using two or more resistors in series to divide the input voltage proportionally. The output voltage is taken across one of the resistors.
- For 2 resistors: Vout = Vin × (R2 / (R1 + R2))
- For 3 resistors: Multiple taps available
- For 4 resistors: Complex voltage division possible
Voltage Divider Applications
- Arduino voltage divider: Level shifting for ADC inputs
- Battery voltage monitoring
- Reference voltage generation
- Sensor interfacing
- LED current limiting
Resistor Voltage Divider Circuit Types
| Type | Configuration | Usage |
|---|---|---|
| 2 Resistor Voltage Divider | R1-R2 series | Basic voltage division |
| 3 Resistor Voltage Divider | R1-R2-R3 series | Multiple output levels |
| 4 Resistor Voltage Divider | R1-R2-R3-R4 series | Complex voltage ratios |
Resistor Selection Guide for Voltage Dividers
Choose appropriate resistors based on these factors:
- Power rating of resistors in voltage divider
- Resistor tolerance impact on output accuracy
- Temperature coefficient for stability
- Standard resistor values availability
- Cost vs precision requirements
Common Voltage Divider Problems
Loading Effect
When load resistance is too low compared to divider resistors, output voltage drops. Solution: Use lower value resistors or buffer the output.
Power Dissipation
Resistors may overheat if power rating is insufficient. Solution: Calculate power dissipation and use appropriately rated resistors.
Accuracy
Resistor tolerance affects output voltage precision. Solution: Use 1% or better tolerance resistors for critical applications.
Practical Applications
- 12V to 5V voltage divider using resistors
- 5V to 3.3V voltage divider for microcontrollers
- Battery voltage monitoring with resistor divider
- Analog sensor scaling with voltage divider
- Reference voltage generation for ADC
Design Calculations
Resistor Power Rating
P(R1) = (Vin - Vout)² / R1
P(R2) = Vout² / R2
Resistor Selection
R2 = (Vout × Rtotal) / Vin
R1 = Rtotal - R2
Voltage Divider Rule Examples
Example 1: Basic Voltage Division
Input: 12V, Required output: 5V
Using standard resistor values:
R1 = 1.4kΩ, R2 = 1kΩ
Output = 12V × (1kΩ / (1.4kΩ + 1kΩ)) = 5V
Example 2: Three Resistor Division
Input: 24V, Required outputs: 12V and 5V
R1 = 1.2kΩ, R2 = 1.2kΩ, R3 = 1kΩ
Output1 = 24V × ((1.2kΩ + 1kΩ) / (1.2kΩ + 1.2kΩ + 1kΩ)) = 12V
Output2 = 24V × (1kΩ / (1.2kΩ + 1.2kΩ + 1kΩ)) = 5V
SMD Resistor Considerations
When using SMD resistors in voltage dividers, consider:
- Package size affects power handling capability
- 0603 resistors typically limited to 0.1W
- 0805 resistors can handle up to 0.125W
- 1206 resistors suitable for 0.25W
- 2512 resistors for high power applications up to 1W
Voltage Divider Design Steps
- Calculate required voltage ratio
- Determine total current requirements
- Select appropriate resistor values
- Calculate power dissipation in each resistor
- Choose resistors with adequate power rating
- Consider temperature effects and derating
- Verify voltage accuracy with actual load
Troubleshooting Guide
Output Voltage Too Low
- Check for excessive loading
- Verify resistor values and tolerance
- Look for damaged resistors
- Check input voltage stability
Resistor Overheating
- Verify power calculations
- Check for proper resistor power rating
- Consider using higher power rated resistors
- Improve ventilation if needed
Quick Reference
Output Voltage
Vout = Vin × (R2 / (R1 + R2))
Output Impedance
Zout = (R1 × R2) / (R1 + R2)
Power Dissipation
P1 = (Vin - Vout)² / R1
P2 = Vout² / R2
Design Tips
Resistor Selection
- Low current: 10kΩ - 100kΩ
- General purpose: 1kΩ - 10kΩ
- High current: 100Ω - 1kΩ
- Precision: 0.1% - 1%
- Power rating: 2-5x calculated
Loading Guidelines
- Rload ≥ 10 × R2
- Iload ≤ Vin / (10 × Rtotal)
- Consider buffer for heavy loads
- Use bypass caps for AC loads
- Monitor power dissipation