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How to Make Chaser Lights

Chaser lights switch on and off one by one, in sequence. They may be made with LEDs, which are light emitting diodes. To make chaser lights, use 741 and 4017 IC -- integrated circuit -- chips. The 741 is an operational amplifier (op-amp) that functions as an astable multivibrator, because it oscillates and generates square waves. Its role is to provide pulses to the 4017 chip. The 4017 is a decade counter that counts the pulses and uses them to switch the LEDs on and off.

Things You'll Need

741 op-amp
4017 decade counter
10 LEDs
330-ohm resistor
10k-ohm resistor
10k-ohm resistor
100k-ohm potentiometer
0.1uF tantalum capacitor
9-volt battery
Battery holder
Breadboard
Jumper wires
Digital multimeter

Instructions

- 1
  Construct the square wave generator first. Place the 741 into the breadboard so its notch faces left, and its two rows of pins straddle the top and bottom sections of the breadboard.
- 2
  Establish one row on the breadboard as the voltage source, and another row as ground. Connect the red lead of the battery holder to the source, and its black lead to ground. Place a wire between the voltage source and pin 7 of the 741. Use a jumper wire to connect pin 4 to ground.
- 3
  Place one end of the 100k resistor at pin 6, and its other end at pin 2. Connect one lead of the capacitor to pin 2 as well, and connect its other lead to ground.
- 4
  Attach the 10k resistor to pins 6 and 3. Connect the middle lead of the potentiometer to pin 3, and its other two ends to the voltage source and ground.
- 5
  Check to see if there is an output voltage at pin 6. Add a jumper wire to pin 3, and place the battery inside of its holder. Turn the multimeter on to DC voltage to see if there is a signal. If not, check to see that the wires are secure, and that the other components are wired correctly. If the signal is found, remove the extra jumper wire, and the battery from its holder.
- 6
  Add the 4017 to the breadboard with the same method used for the 741. Make sure that the ICs are not too close to each other.
- 7
  Wire the 4017 to the circuit. Use a jumper wire to attach an LED to pin 3 so that its positive lead faces the chip but its negative lead faces away. The leads must be placed in different columns, and the LED must be placed perpendicular to the 4017. Use the same method to attach LEDs to pins 2, 4, 7, 10, 1, 5, 6, 9, and 11 of the 4017 chip.
- 8
  Attach the 330 resistor between the negative side of the pin 3 LED and ground. Wire the negative sides of the other LEDs to ground.
- 9
  Connect pins 8, 13, and 15 to ground, and connect pin 16 to the voltage source. Add a jumper wire between pin 6 of the 741 and pin 14 of the 4017. Place the battery inside of the holder. When the potentiometer knob is adjusted properly, the LEDs will turn on and off.

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