Thames & Kosmos Electronics - Page 41

Flashers
EXPERIMENT 

Hands as “flash
regulators”
YOU WILL NEED
 your flasher circuit from
Experiment 14
  long wire connectors
  resistor, . kΩ
HERE’S HOW
1. Remove the 100-kΩ resistor from the
flasher circuit again, and replace it
with the 3.3-kΩ resistor.
2. Insert the long wires.
3. Take the two bare wire ends
between your moistened thumb
and forefinger.
What do you observe?
+
–
9V
T2
T1
R 2
220 kΩ
R 1
3.3 kΩ
+
10 µF
C 2
+
100 µF
C 1
LED 1
R 4
470 Ω
R 3
470 Ω
LED 2
Depending on how moist your
fingers are, the LEDs will blink
faster or slower. So you can
regulate their flashing speed by
using your skin resistance!
 WHAT’S HAPPENING?
LED1
LED2
T1
+
+
+
–
T2
A
A
C
C
R2
 kΩ
C1  µF
R3  Ω
C2  µF
R
. kΩ
R
 Ω