CURRENT LIMITING RESISTOR CALCULATOR

FOR LIGHT EMITTING DIODES

  The calculators on this page can be used to find current limiting resistors and currents for Light Emitting Diodes.

  The first calculator determines the resistance for a desired LED current while the second calculates the current for a given resistance.


LED - Current and Resistance Calculator Diagram

LED - CURRENT LIMITING RESISTOR CALCULATOR

Supply Voltage

VOLTS
Voltage Drop Across LED

VOLTS
Desired LED Current

MILLIAMPS
Calculated Limiting Resistor

OHMS
Calculated Resistor Wattage

WATTS

LED - CURRENT CALCULATOR

Supply Voltage

VOLTS
Voltage Drop Across LED

VOLTS
Resistor Value

OHMS
Calculated LED Current

MILLIAMPS
Calculated Resistor Wattage

WATTS

Voltages in Volts - Current in Milliamps - Resistance in Ohms

When selecting resistors - It is advisable to choose the next higher standard value.

A browser capable of running Javascript is required for this calculator.

  If LED's are connected in series - ADD their voltage drops together to get the total voltage drop.

  Entering a zero for the LED voltage drop will yield the resistance and wattage for a resistance only circuit.



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Please Read Before Using These Circuit Ideas

  The explanations for the circuits on these pages cannot hope to cover every situation on every layout. For this reason be prepared to do some experimenting to get the results you want. This is especially true of circuits such as the "Across Track Infrared Detection" circuits and any other circuit that relies on other than direct electronic inputs, such as switches.

  If you use any of these circuit ideas, ask your parts supplier for a copy of the manufacturers data sheets for any components that you have not used before. These sheets contain a wealth of data and circuit design information that no electronic or print article could approach and will save time and perhaps damage to the components themselves. These data sheets can often be found on the web site of the device manufacturers.

  Although the circuits are functional the pages are not meant to be full descriptions of each circuit but rather as guides for adapting them for use by others. If you have any questions or comments please send them to the email address on the Circuit Index page.

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19 July, 2008