Maker Factory ELECTRONICS EXPERIMENTS BOX Manual page 222

Circuit 199: Infrared receiver
Setup information
Install the transistor, the diode and the resistor as shown in Fig. 2.199 followed by the four jumper wires.
Check the placement on the board again and only then connect the battery.
Experiment
The best way is to build the IR transmitter of our previous circuit together with this one on a shared bread-
board. This allows you to align the IR diode and the phototransistor facing each other so that the infrared
light travels directly into the phototransistor. If everything is wired correctly, the IR diode emits a strong
light within the infrared range. The phototransistor responds and the red LED turns on. A cardboard piece
held between IR diode and phototransistor blocks the beam of light, and the red LED turns off. If the LED
is replaced by a suitable relay, you could use it to remotely turn on and off a self-built tube amplifier, for
example.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.199.
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Components required:
1 x PT331C phototransis-
tor, 1 x red LED, 1 x 1 kΩ
resistor, 1 x breadboard,
1 x 9V battery with clip
connector
Fig. 2.199: Infrared receiver