156
Circuit 131:
15 seconds switch-off delay
Setup information
Install the two transistors, the diode, the three resistors and the electrolytic capacitor as shown in
Fig. 2.131
The six jumper wires come next followed by the jumper, which serves as a switch (shown dashed). For your
guidance, we labelled the “switch” with
Start.
Check the placement on the board again and only then con-
nect the battery.
Components required:
2 x 2N3904 transistors,
1 x BAT85 Schottky
diode, 1 x red LED,
1 x 1 k
Ω
resistor,
1 x 220 k
Ω
resistor,
1 x 1 M
Ω
resistor,
1 x 100 μF elec-
trolytic capacitor,
1 x breadboard, 1 x 9V
battery with clip con-
nector
Fig. 2.131:
15 seconds switch-
off delay
Experiment
Even if everything is wired correctly, nothing will happen at first. But when you activate, which means clos-
ing the
Start
switch, the red LED will go on after a short delay. The delay time in our case is about 15 sec-
onds. When the “switch” is opened again, the red LED turns off. This basically is equivalent to the switch off
delay. The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.131.
Summary of Contents for ELECTRONICS EXPERIMENTS BOX
Page 4: ......
Page 265: ...267 Fig 3 56 Cir cuit 56 Audio limiter Fig 3 57 Circuit 57 Amplifier for a storm detector...
Page 269: ...271 Fig 3 64 Circuit 64 Stabilizer for 1 9 V Fig 3 65 Circuit 65 Stabilizer for 2 5 V...
Page 275: ...277 Fig 3 80 Circuit 80 Quiztimer 30 seconds Fig 3 81 Circuit 81 Handy diode tester...
Page 315: ...317 Fig 3 179 Circuit 179 HF generator 150 kHz Fig 3 180 Circuit 180 HF generator 420 kHz...
