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LED Calculator

Logic & Formula

An LED needs a current-limiting resistor to prevent burnout. The resistor drops the excess voltage.

R = Vs − (Vf × n)If

Vs = source voltage, Vf = LED forward voltage, n = LEDs in series, If = desired current.

Quick Setup
LED Color
Source Voltage
?
Power supply voltage (5V for Arduino, 3.3V for ESP32, 9V/12V battery).
V
Forward Voltage
V
Forward Current
mA
LEDs in Series
255 (100%)
0 (OFF) 64 128 192 255 (MAX)
Calculated Resistance
150 Ω
Nearest E24: 150Ω
Power: 60mW
sketch.ino 

          

        

      


    


    
    


      
      

        

          
            RGB LED Basics
            
              
                
              
            
          
          

            
An RGB LED contains three separate dies (Red, Green, Blue) sharing a common pin. Each channel needs its own current-limiting resistor.

            
Common Cathode: shared GND pin, HIGH = ON.

              Common Anode: shared V+ pin, LOW = ON (PWM inverted).

            
Typical Vf: Red ≈ 2.0V, Green ≈ 3.2V, Blue ≈ 3.2V

          

        

      


      
      

        LED Type
        

          
          
        

      


      
      

        Quick Setup
        

          
          
          
          
        

      


      
      

        

          Source Voltage
          

            
            
            V
          

        

        

          Forward Current
          

            
            
            mA
          

        

      


      
      

        Color
        
      


      
      

        
        
        
        
        
        
        
      


      
      

        Calculated Resistances
        

          

          

            
            

              

                

                Red (Vf 2.0V)
              

              

                150
                Ω
                E24:
                150Ω
              

            

            
            

              

                

                Green (Vf 3.2V)
              

              

                90
                Ω
                E24:
                91Ω
              

            

            
            

              

                

                Blue (Vf 3.2V)
              

              

                90
                Ω
                E24:
                91Ω
              

            

            

              Total Power:
              0mW
            

          

        

        

      


      
      

        
        

          

            

              

                

                  

                  

                  

                

                rgb_led.ino
              

              
            

            

          

        

      


    


  


  
  

    

      
      

      


      

        
      

    

  



  

  
  

    
    

    
    

      
      

        
      


      
      

        

          

            
          

          
          

            

          

        

      


      
      

        

          

          

            

              #
              
            

            

              

                R
                
              

              

                G
                
              

              

                B
                
              

            

          

        

      


      
      

        Presets