Instructables
Picture of How to make an alternating LED flasher
Using the 4001 quad nor gate CMOS IC and a few other basic parts, build this simple alternating  LED  flasher.
 
 
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Step 1: Parts

Picture of Parts
-4001 quad nor gate
-2.2k resistor
-1meg resistor
-1k resistor
-10 uF capacitor
-100k pot
-Solid core wire
-Breadboard
-2 LEDs

Step 2: Insert the IC and jumpers

Picture of Insert the IC and jumpers
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Insert the IC over a slot in the breadboard and make jumpers.  Connect pins 1 and 2, 5 and 6, and than 3 to 5. Pin 7 goes to ground.  Finally, pin 14 connects to 6 volts. 

Step 3: Components

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That 10 uF cap connects to pin 4 (+) and an open row closest to the IC (-).  The 2.2k resistor connects to the same row of the negative on the capacitor.  Connect the 1meg resistor to that same row and that to pin 1.  Connect one of the LEDs anodes to pin 4 and the cathode to a free row.  Connect the other LEDs anode to pin 5, 3 or 6 and the cathode to the same row as the others.  Connect the 1k resistor to that same row and then to ground. 

Step 5: Schematic

Picture of Schematic

Step 6: Troubleshooting

If the circuit fails to work;

-Check if the IC is hot.  If so make sure its not inserted backwards or that the power connections are reversed
-Make sure the LEDs and the capacitor are not in backwards
-If it still fails to operate take apart the circuit ad build it again!