Elenco Projects 306-511 - Manual (Page 31)

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Project #381
OBJECTIVE: To construct a time delay circuit.
Turn on the slide switch (S1) and the bulb (L2) does not light. Press
switch (S2) and slowly the bulb lights.
When the press switch is pressed, current flows to the base of the
transistor (Q2) and charges the 100
μ F capacitor (C4). When the
capacitor charges up to more than 1 volt, the transistor (Q2) turns on
and triggers the SCR (Q3). The bulb will stay lit until the slide switch
is turned off. The values R5 and C4 determine the time it takes until
the transistor turns on. The larger the capacitor value, the more time
it takes to turn on.
Delay Light
Project #382 Project #383
OBJECTIVE: To construct a time delay fan.
Delay Fan
OBJECTIVE: To build a sound
activated fan.
Sound Activated Fan
Use the circuit in project #381. Replace the lamp (L2) with the motor
(M1) and fan, then replace the 3-snap (base grid locations E6-G6) with
the lamp (L2). Turn on slide switch (S1) and press down the press switch
(S2) to start the motor.
Now replace the 100 μ F capacitor (C4) with the 470 μ F capacitor (C5).
Turn on slide switch (S1) and press switch (S2). See how long it takes
until the motor (M1) spins.
Build the circuit as shown. Place
the fan on the motor (M1). Set
the lever on the adjustable
resistor (RV) toward towards the
100k
Ω resistor (R5). Clap to
start the motor.
!
WARNING: Moving parts. Do not touch the fan or
motor during operation. Do not lean over the motor.
To learn more about how circuits work, visit www.snapcircuits.net or page 62 to find out about our Student Guides.
!
WARNING: Moving parts.
Do not touch the fan or
motor during operation. Do
not lean over the motor.