We’ve seen how a capacitor’s charge/discharge
cycle can be used to delay certain circuit operations.
Now let’s delay the oscillator action in this project
with a 470
μ
F capacitor.
When you press the key, the capacitor discharges.
When you release the key, the capacitor begins to
charge. The circuit continues to oscillate until the
capacitor is charged, then current stops flowing.
When you close the key for the second time, it
immediately discharges the capacitor.
A discharged capacitor has an equal number of
electronics on its positive (+) and negative (–)
electrodes. A charge is stored in a capacitor by
drawing electrons from the positive electrode (to
actually make it positive) and an equal number of
electrons are added to the negative electrode (to
make it negative). The current that flows to charge
the capacitor is called charging current or
displacement current. When the capacitor is
discharging, the same amount of current must flow
in the opposite direction. This current is called
discharge current or displacement current.
If you have a VOM, use it to measure the charge on
the capacitor with the voltmeter function. The
displacement current can be measured with the
current function.
Only the capacitor has this unique storage-action.
We can use capacitors to perform many functions
using this characteristic. However, this storage-
action makes capacitors in very high voltage circuits
dangerous sources of possible shock or
electrocution. Play it safe? You should discharge
capacitors before touching them if they use voltages
above 50V.
Notes:
EXPERIMENT #61: OSCILLATOR WITH TURN-OFF DELAY
Schematic
-79-
Wiring Sequence:
o
1-29
o
2-30
o
3-85-105-109
o
4-120
o
5-41-110
o
40-106-86
o
42-118-137
o
117-138-119
Summary of Contents for EP-130
Page 11: ... 11 I ENTERTAINMENT CIRCUITS ...
Page 26: ... 26 II BASIC SEMICONDUCTOR AND COMPONENTS CIRCUITS ...
Page 36: ... 36 III LED DIGITAL DISPLAY CIRCUITS ...
Page 41: ... 41 IV A TOUR THROUGH DIGITAL CIRCUITS ...
Page 49: ... 49 V MORE ADVENTURES WITH DIGITAL CIRCUITS ...
Page 64: ... 64 VI THE WORLD OF TRANSISTOR TRANSISTOR LOGIC ...
Page 77: ... 77 VII APPLICATION CIRCUITS BASED ON THE OSCILLATOR ...
Page 88: ... 88 VIII BASIC OPERATIONAL AMPLIFIER CIRCUITS ...
Page 116: ... 116 IX MORE ADVENTURES WITH OPERATIONAL AMPLIFIERS ...
Page 129: ... 129 X COMMUNICATION CIRCUITS ...