Maker Factory ELECTRONICS EXPERIMENTS BOX Manual page 77

Circuit 54: Light sensitive switch with solar cell
Setup information
Install the two transistors, the LED and the two resistors as shown in Fig. 2.54. The three jumper wires
come next. Last but not least connect the solar cell. Check the placement on the board again and only then
connect the battery.
Experiment
This circuit tells you whether the sensor surroundings are bright or dark. The sensor functions as solar cell.
Strong illumination delivers a voltage up to 4V. This triggers transistor T1 and the red LED light turns on. It
can be utilised in many ways: Light barriers, remote release for animal photos, room surveillance and the
like. With some adapted wiring, also an exposure meter for photographers could be accomplished.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.54.
Components required:
2 x 2N3904 transistors,
1 x solar cell, 1 x red LED,
1 x 1 kΩ resistor, 1 x 10 kΩ
resistor, 1 x breadboard,
1 x 9V battery with clip
connector
Fig. 2.54: Light sensitive switch
with solar cell
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