Elenco Electronics SNAP CIRCUITS SKILL BUILDER - Project 112 The Dark Dimmer; The Dark Dimmer Circuit; Project 113 Lagging Light; Lagging Light Circuit

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This circuit shows how capacitors
can be used to provide a delay.
This type of circuit is used in house
lighting to fade out the lights when
you turn the switch off.
The Dark Dimmer
Turn on the slide switch (S1) and push the press switch (S2). If there
is light on the photoresistor (RP), then the LED (D1) will stay on for a
long time after you release the press switch.
The energy stored in the 470mF capacitor (C5) keeps the controlling
current to the NPN transistor (Q2) on even though the press switch
was turned off. If it is dark, the high resistance of the photoresistor
shuts off the current to the transistor.
Lagging Light
Build the circuit and turn on the slide switch (S1). The LED (D1) is
bright but slowly gets dark as the 470mF capacitor (C5) charges up.
The LED will stay dark until you push the press switch (S2), which
discharges the capacitor.
Project 113
Project 112