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How to Make an LED Blink With Sound

Light-emitting diodes (LEDs) are semiconductors that emit light when given a voltage. They can be driven by circuits that force them to blink on and off. They can also be made to blink with the use of sound. One way to do this is to attach an LED directly to speaker wires. The wires provide enough voltage so that the LED can light up without a battery. To make an LED blink with sound, attach an LED to a speaker and drive the speaker with a pulse generator. Use an integrated circuit chip such as a 555 timer.

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Things You'll Need

555 IC timer
LED
10uF capacitor
33uF capacitor
100uF capacitor
1k-ohm resistor
100k-ohm potentiometer
4 AA batteries
Battery holder
Solderless breadboard
Jumper wires
Alligator clips

Instructions

- 1
  Orient the breadboard so that it is parallel. Choose two rows that will serve as the positive voltage and ground.
- 2
  Connect the 555 timer to the breadboard. Place it horizontally in the middle so that one row falls into the top section, and the other into the bottom section. The notch on its top should face left so that pins 1 through 8 run counterclockwise.
- 3
  Connect pin 4 to the positive voltage row. To do this, place one end of a jumper wire into one of holes in the pin 4 column, then connect its other end to one of the holes next to the positive row. Do the same procedure to connect pin 8 to the circuit.
- 4
  Wire pins 1, 6 and 7. First attach pin 1 to ground, then insert one end of a jumper wire at pin 2 and the other end at pin 6.
- 5
  Attach one end of the 1k resistor to pin 2 and its other end to pin 7. Insert the positive side of the 100uF capacitor at pin 2, then use a jumper wire to connect its other end to ground.
- 6
  Connect one end of the potentiometer to pin 8. Connect the wiper, which is its middle part, to pin 7.
- 7
  Connect the speaker to the breadboard by placing one of its leads at pin 3 and its other lead at ground. If the speaker is too close to the circuit, move it a few columns away and attach it to the openings with the use of a jumper wire.
- 8
  Attach the positive lead of the LED directly to the end of the speaker wire that is connected to pin 3. Use an alligator clip to do so. If necessary, strip some of the insulation from the speaker wire first. Attach the negative lead of the LED to the other end of the speaker wire.
- 9
  Connect the red lead of the battery holder to positive voltage and its other end to ground. Add the battery to the holder and the LED will light. Rotate the knob of the potentiometer back and forth to control the pulse rate. Exchange the 100uF capacitor with the 33uF, then the 10uF. In each case, adjust the potentiometer knob.

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