Introduction: LED Counter
You can make an attractive LED counter that has various frequencies with a few simple electronic components.
Step 1: Place the Flasher IC
Position the LM3909N IC about three rows of holes from the left side of the solderless breadboard assembly. Also, make sure one-half of the IC is above and one-half is below the central depression in the solderless breadboard assembly. Press down on the IC to force the pins into the holes. All of the pins should be checked for ones that are bent or folded up. If the pins do not make good contact with the solderless breadboard, the circuit may not work.
Step 2: Connect Pin 1 to Pin 8
Prepare and insert a jumper wire that will connect Pin 1 to Pin 8.
The pins are numbered anti-clockwise around the IC (chip) starting near the notch or dot.
The green line in the illustration.
Step 3: Insert the Capacitor
Look for the markings of positive and negative on the capacitor. Insert the electrolytic capacitor into the circuit board so the positive side is in one of the holes immediately below pin 2 of the IC. The other lead of the capacitor should be connected to Pin 1 of the IC.
The purple lines in the illustration.
Step 4: Insert the LED
Insert the light-emitting diode. The marked side of the diode must look to the negative side of the source. To insert the LED correctly, the marked side of the diode must connect to Pin 8. The other lead from the diode connects to Pin 6 of the IC.
The bluegreen lines in the illustration.
Step 5: Connect Pin 5 to Positive
Connect a jumper wire from Pin 5 of the IC to the top horizontal of X track on the solderless breadboard assembly. The entire top horizontal or X track is to be at +1.5 volts.
The red line in the illustration.
Step 6: Connect Pin4 to Negative
Connect a jumper wire from Pin 4 to the bottom horizontal or Y track. This track will serve as the ground.
The blue line in the illustration.
Step 7: Ready to Put Battery In
You are now ready to connect the battery. Connect the negative terminal to the battery to the bottom horizontal or Y track of the board. Connect the positive terminal to the top horizontal to X track of the solderless breadboard. The LED should start flashing.
The 3909N IC only needs a 1.5V battery (AA), so you can use a battery holder to help keep the battery in place.
Step 8: To Change the Speed of Flashing Rate
In the LM3909 IC, electrons from the battery pass through a resistor and charge up the capacitor. The size of the capacitor determines how long it will take for the capacitor to charge.
You can easily change the increasing the flashing rate by having a smaller capacitor. Or a slower flashing rate with a larger capacitor.
Different colors of LED also has a different rate, too.
For my LED Counter, I used 220m capacitor for the yellow LED, which is flashing about every second, and 330m for the slower red LED on top, and 100m for the faster red LED at the bottom.
For more information on my LED flasher, you can visit my site at http://dma.sjsu.edu/~art103/Students/chen/LEDclock.html