VMA502
V. 02 – 05/04/2019
10
©Velleman nv
Programming Code
Result
After programming, the buzzer should ring.
7.5
The Phototransistor
A phototransistor is a transistor the resistance of which varies according to different light strengths. It is based
on the photoelectric effect of a semiconductor. If the incident light is intense, the resistance reduces; if the
incident light is weak, the resistant increases. A phototransistor is commonly applied in the measurement of
light, light control and photovoltaic conversion.
Let’s start with a relative simple experiment. The phototransistor is an element that changes its resistance as
light strength changes. Refer to the PWM experiment, replacing the potentiometer with a phototransistor. When
there is a change in light strength, there will be a corresponding change on the LED.
Required Hardware
1 x phototransistor
1 x red M5 LED
1 x 10KΩ resistor
1 x 220 Ω resistor
1 x breadboard
jumper wires as needed
