Electronic pulses are handy for testing audio equipment as well as driving digital and computer-related circuits. An ideal pulse rises instantly from zero volts to some nominal value, such as five volts, remains there for a predictable amount of time, then drops instantly back to zero before repeating its cycle. Pulses come in a wide range of frequencies, from less than one per day for timing experiments to billions per second to run a modern-day personal computer. The 74LS14 Schmitt hex inverter integrated circuit, or IC, has six logic inverters; you need only one, plus two other components, to build a very simple pulse generator.
- 74LS14 Schmitt hex inverter integrated circuit
- Solderless breadboard
- 4 12-inch pieces of 22-gauge wire
- 5-volt DC power supply
- 680K-ohm, 1/4-watt resistor
- 1-microfarad, 35-volt capacitor
Set the 74LS14 IC into the breadboard. It fits into the horizontal slot in the board so the legs are on either side of the slot. Press it in carefully, keeping the legs straight.
Insert one end of a 12-inch wire so it connects to the IC's pin 14. Connect the other end to the DC power supply's positive terminal. Insert the end of a second wire so it connects to the IC's pin 7. Connect the other end to the power supply's ground terminal. Insert the end of a third piece of wire so it connects to pin 7. Connect the fourth wire to pin 2.
Set the leads of the capacitor so one connects to pin 1 and the other connects to pin 7. Insert the resistor so it connects between pins 1 and 2.
Clip the oscilloscope's probe to the wire connected to pin 2. Connect the probe's ground clip to the remaining wire coming from pin 7. Turn the oscilloscope and 5-volt power supply on. Set the oscilloscope's sweep speed to 1 millisecond per division. You should see the pulses on the oscilloscope screen.
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