LED sequencer

PARTS AND MATERIALS

• 4017 decade counter/divider (Radio Shack catalog # 276-2417)
• 
• 555 timer IC (Radio Shack catalog # 276-1723
• 
• Ten-segment bargraph LED (Radio Shack catalog # 276-081)
• One SPST switch
• One 6 volt battery
• 10 kΩ resistor
• 1 MΩ resistor
• 0.1 µF capacitor (Radio Shack catalog # 272-135 or equivalent)
• Coupling capacitor, 0.047 to 0.001 µF
• Ten 470 Ω resistors
• Audio detector with headphones

Caution! The 4017 IC is CMOS, and therefore sensitive to static electricity!

Any single-pole, single-throw switch is adequate. A household light switch will work fine, and is readily available at any hardware store.

The audio detector will be used to assess signal frequency. If you have access to an oscilloscope, the audio detector is unnecessary.

LEARNING OBJECTIVES

• Use of a 555 timer circuit to produce "clock" pulses (astable multivibrator)
• Use of a 4017 decade counter/divider circuit to produce a sequence of pulses
• Use of a 4017 decade counter/divider circuit for frequency division
• Using a frequency divider and timepiece (watch) to measure frequency
• Purpose of a "pulldown" resistor
• Learn the effects of switch contact "bounce" on digital circuits
• Use of a 555 timer circuit to "debounce" a mechanical switch (monostable multivibrator)

SCHEMATIC DIAGRAM