Elenco Circuit Maker Sound Plus 200 - Manual (Page 38)

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Project #72 Light Alarm
Modify the circuit in the preceding project
by replacing the LED (D1) with the 4.5V
lamp (L4) and replacing the 5.1KW resistor
(R3) with the 100W resistor (R1). It works
the same way but is brighter now.
Build the circuit with the jumper connected as
shown, and turn it on. Nothing happens. Break the
jumper connection and the light turns on. You could
replace the jumper with a longer wire and run it
across a doorway to signal an alarm when someone
enters.
Project #73
Brighter
Light Alarm
Press the press switch (S2) to complete the current’s path flow. You
might expect the LED (D1) to light instantly but it doesn’t. The charging
current flows into the 100mF capacitor (C4) first. As the capacitor
charges, the charging current decreases, input current to the PNP
transistor (Q1) increases. So current begins to flow to the LED and the
LED gradually brightens.
Now release the press switch. The capacitor begins to discharge,
sending input current to the transistor. As the capacitor discharges, the
input current reduces to zero and gradually turns off the LED and the
transistor.
Light Dimmer
+
Project #74
CM-200_Manual_031914.qxp_CM-200_Manual_031914 4/2/14 12:04 PM Page 38