Thames & Kosmos Electronics - Lengthening the cycle time

EXPERIMENT 

Lengthening the
cycle time
YOU WILL NEED
 your timer from
Experiment 9
 capacitor  µF
The cycle time is determined by the
electrolytic capacitor you install in the
switch circuit. Because the newly-
installed 100-µF capacitor has ten times
the capacitance of the 10-µF one used in
Experiment 9, the result is about ten
times the cycle time.
 WHAT’S HAPPENING?
HERE’S HOW
1. Replace the 10-µF capacitor in
your timer switch with the
100-µF one.
2. Connect the battery and wait until
the timer is ready.
3. Press once on the pushbutton.
What has changed since
Experiment 9?
+
–
9V
T2
T1
R 2
22 kΩ
R 1
3.3 kΩ
R 5
220 kΩ
R 3
470 Ω
R 4
100 kΩ
+
100 µF
C 1
Ta 1
LED 1
R 6
470 Ω
LED 2
LED1
LED2
T1
Pb1
+
–
T2
A AC C
R1
. kΩ
R
 Ω
C1  µF
R
 kΩ
R
 Ω
R
 kΩ
R4
 kΩ
+