Elenco Electronics 202 - Manual (Page 98)

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Project #229 Adjustable Time Delay Lamp
OBJECTIVE: To build a lamp that
stays on for a while.
OBJECTIVE: To build a fan
that stays on for a while.
Replace on battery holder (B1) with a 3-
snap and replace the lamp (L2) with the
motor (M1), be sure to put on the fan.
Turn on the slide switch (S1) and press
the press switch (S2). The fan stays on
for a while after you release the press
switch. You can change the delay time
with the adjustable resistor (RV).
Turn on the slide switch (S1) and
press the press switch (S2). The
lamp (L2) stays on for a while after
you release the press switch. You
can change the delay time with the
adjustable resistor (RV).
Project #230
Adjustable
Time Delay Fan
Project #231 Transistor Fading Siren
OBJECTIVE: To build a siren that
slowly fades away.
OBJECTIVE: To build a
doorbell that slowly fades away.
Replace the alarm IC (U2) with
the music IC (U1). The circuit
has a doorbell sound that plays
and stops.
Turn on the slide switch (S1), then
press and release the press switch
(S2). You hear a siren that slowly
fades away and eventually goes off.
You can modify this circuit to make
machine gun or ambulance sound
instead like in the other projects. You
can also replace the 10
μF capacitor
(C3) with the 100 μF (C4) or 0.1μF
(C2) to greatly slow down or speed
up the fading.
Project #232
Fading
Doorbell
!
WARNING: Moving parts.
Do not touch the fan or
motor during operation.