gottlos Posted February 2, 2006 Report Share Posted February 2, 2006 i need help with a simple circuit Quote Link to comment Share on other sites More sharing options...
audioguru Posted February 2, 2006 Report Share Posted February 2, 2006 Hi Got Lost,Welcome to our forum. ;DYour 555 LED flasher circuit doesn't have enough supply voltage for the voltage requirement of a blue LED plus the voltage loss at the high output of the 555.A blue LED's voltage requirement could be 3.6V. The voltage loss at the output high of a 555 could be 2.25V, but is typically 1.4V.3.6V + 1.4V= 5V so only 1V is across the 330 ohm current-limiting resistor resulting in only 3mA. If your 555 has a voltage loss of 2.25V then the LED's current is only 455uA.The circuit's supply voltage was probably selected for it to use 1.8V red LEDs, wasn't it?Have you checked that the LED and capacitor aren't installed backwards? Quote Link to comment Share on other sites More sharing options...
gottlos Posted February 3, 2006 Author Report Share Posted February 3, 2006 capacitor and leds are in correct, and yes it is for the red leds. thanks for the help Quote Link to comment Share on other sites More sharing options...
trigger Posted February 3, 2006 Report Share Posted February 3, 2006 You can try using a transistor at the 555 output pin for switching and tie the blue LED to 6V with a resistor. Quote Link to comment Share on other sites More sharing options...
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