Experiment 9: Time and Capacitors

Chapter Experiment 9: Time and Capacitors

Make Electronics Book Learning by Discovery
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Make Electronics Book Learning by Discovery

  • Experiment 9: Time and CapacitorsChapter 268Experiment 9: Time and CapacitorsYou will need:• AC adapter, breadboard, wire, wire cutters, and strippers.• Multimeter.• Pushbutton, SPST. Quantity: 1.• Resistors and electrolytic capacitors, assorted.In 75,Experiment 8, when you put a capacitor in parallel with the coil of the relay, the capacitor charged almost instantly before discharging itself through the relay coil. If you add a resistor in series with a capacitor, the capacitor will take longer to charge. By making a capacitor take longer to charge, you can mea-sure time, which is a very important concept.Clean the components off your breadboard and use it to set up the very simple circuit shown in Figure 2-78, where C1 is a 1,000 µF capacitor, R1 is a 100K resis-tor, R2 is a 100Ω resistor, and S1 is the pushbutton that you used previously. Set your meter to measure volts DC, place the probes around the capacitor, and hold down the pushbutton. You should see the meter counting upward as the voltage accumulates on the capacitor. (This is easier with a meter that doesn’t have autoranging, because you won’t have to wait while the meter figures out which range to apply.) Resistor R1 slows the charging time for the capacitor. Figure 2-78. Watch the voltage building up on the capacitor while you hold down the pushbutton. Substitute other values for R1, discharge the capacitor by touching R2 across it, and then repeat your measure-ment process. S1: Momentary pushbutton, OFF (ON) R1: 100K initially R2: 100Ω C1: 1,000 µFS1R1C1R2Volts12vDC