78
2.22 Light sensitive switch
Circuit 53:
Light sensitive switch with green LED
Setup information
Install the two transistors, the two diodes and the two resistors as shown in
Fig. 2.53
. The three jumper
wires come next. Check the placement on the board again and only then connect the battery.
Components required:
2 x 2N3904 transistors,
1 x green LED, 1 x red LED,
1 x 1 k
Ω
resistor,
1 x 100 k
Ω
resistor,
1 x breadboard, 1 x 9V bat-
tery with clip connector
Fig. 2.53:
Light sensitive switch
with green LED
Experiment
This circuit tells you whether the sensor surroundings are bright or dark. The green LED functions as sensor.
Its reverse current increases noticeably when light shines on the sensor. This will turn on the red LED. It can
be utilised in many ways: Light barriers, remote release for animal photos, room surveillance and the like.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.53.
Summary of Contents for ELECTRONICS EXPERIMENTS BOX
Page 4: ......
Page 265: ...267 Fig 3 56 Cir cuit 56 Audio limiter Fig 3 57 Circuit 57 Amplifier for a storm detector...
Page 269: ...271 Fig 3 64 Circuit 64 Stabilizer for 1 9 V Fig 3 65 Circuit 65 Stabilizer for 2 5 V...
Page 275: ...277 Fig 3 80 Circuit 80 Quiztimer 30 seconds Fig 3 81 Circuit 81 Handy diode tester...
Page 315: ...317 Fig 3 179 Circuit 179 HF generator 150 kHz Fig 3 180 Circuit 180 HF generator 420 kHz...
