LED Indicates Two Power States


Posted on Nov 25, 2012

The circuit in Fig. 1 uses a single bicolor LED to indicate both power-on and blown-fuse conditions. Regardless of the condition of the fuse, the green side of the LED is always on for each positive half-cycle of the ac input. With a 120Vrms ac input the average diode current is a little more than 10mA. If the fuse is good, current cannot flow through the red side because the good fuse shorts out this side. If the fuse is blown, the ac mains voltage is across the fuse terminals. This condition allows current to flow through the red side of the LED during the negative half cycle of the ac input. The result is a yellow LED. There are some losses in the transformer, but you can adjust the current setting resistor on the red side of the LED for best color.






Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Self oscillating flyback converter
    Add-on-telephone-hold-button
    Geiger Counter Ii Circuit
    Stablised Power Supply With Short Circuit Indication
    Night light Wake up Alarm Combo circuit
    Sounds From The Old West
    Transistor Testers
    Ultrasonic remote control switch lighting circuit
    Homemade disinfectant circuit
    Application of IR2130 three-phase fixed frequency output of the power supply system wiring diagram



    Top