80
Circuit 55:
Light sensitive switch with phototransistor
Setup information
Install the three transistors, the LED and the two resistors as shown in
Fig. 2.55.
The five 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 PT331C phototransistor,
1 x red LED, 1 x 1 k
Ω
resis-
tor, 1 x 100 k
Ω
resistor,
1 x breadboard, 1 x 9V bat-
tery with clip connector
Fig. 2.55:
Light sensitive switch
with phototransistor
Experiment
This circuit tells you whether the sensor surroundings are bright or dark. The sensor functions as phototran-
sistor. When lit, this becomes electrically conductive. Transistor T1 is thus triggered and the red LED turns
on. It can be utilised in many ways: Light barriers, remote release for animal photography, room surveil-
lance and the like. With wiring adapted, also an exposure meter for enthusiastic photographers could be
accomplished.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.55.
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...
