Velleman EDU01 - Manual (Page 13)

www.vellemanprojects.com Pag. 13
Required parts: 9V battery*, 1K resistor (brown black red gold), 470K resistor (yellow
purple yellow gold), red LED, BC547 transistor, wire jumper.
How it works: In this circuit, the small
current flowing through your finger will be
amplified by the transistor.
The base current that runs via your finger
and resistor R1, is amplified by transistor T1.
The amplified current flows through the LED
and R2 making the LED lit.
R3 will prevent the transistor for unwanted
functioning.
HINT: wet you finger to make the LED
light up stronger.