01 Flashing Bicolor LED

This is how I drive a bicolor LED with a common cathode. This circuit allows the bicolor LED to flash in intervals RED-GREEN-RED-GREEN.... assuming the LED is a red green bicolor LED.

1. A 555 timer was used to provide the pulse and timing for the intervals.
2. The LED on the left is connected directly to the output Pin 3, while the LED on the right is connected to a simple resistor-transistor logic NOT GATE.
3. Left LED will light when the output is HIGH; Right LED will light when output is LOW.
4. Assuming the 555 timer can source up to 200mA, a maximum 10, 20mA LED can be connected in parallel.

reference:
NOT gate/ inverter
http://www.play-hookey.com/digital/experiments/rtl_inverter.html

email:
shlim90@gmail.com