Thames & Kosmos Electronics - Flip-flop circuit

EXPERIMENT 

Flip-flop circuit
YOU WILL NEED
 your alarm system from
Experiment 5
When you touch B, the LED still lights up.
But as soon as you press the pushbutton,
the LED goes out. You can repeat this
little game as many times as you like. The
circuit always remembers the last state
— in other words, it stores it.
 WHAT’S HAPPENING?
HERE’S HOW
1. Pull the long wire out of contact
clip A.
2. Briefly touch the free end of the
wire against the base terminal (B) of
the right T2 transistor.
What do you notice?
3. Now press the pushbutton.
Do you notice a change?
Flip-flop
Your alarm system is a
modified “flip-flop”
circuit. A flip-flop is a fully
automatic electronic
switch of a type that is
very often used in
electronic equipment
— such as in the memory
cells of computers.
LED1
LED2
A
B
T1
Pb1
+
–
T2
A
A C
C
R1
 Ω
C1
 µF
R
. kΩ
R
 kΩ
R
 Ω
R
 kΩ
C1
 µF
R
 kΩ
+