228
Circuit 203:
7 seconds switch-off delay
Setup information
Install the transistor, the diode, the four resistors and the electrolytic capacitor as shown in
Fig. 2.203
fol-
lowed by the three jumper wires and the jumper, which serve as switch (shown dashed). For your guidance,
we labelled the “switch” with
Start.
Check the placement on the board again and only then connect the
battery.
Components required:
1 x 2N3904 transistor,
1 x red LED, 2 x 1 k
Ω
resis-
tors, 1 x 10 k
Ω
resistor,
1 x 100 k
Ω
resistor,
1 x 100 μF electrolytic
capacitor, 1 x breadboard,
1 x 9V battery with clip
connector
Fig. 2.203:
7 seconds switch-off
delay
Experiment
Even if everything is wired correctly, nothing will happen at first. But when you activate the
Start
switch,
that is, when you insert the wire, the red LED will go on after a short delay. When the “switch” is opened
again, the red LED will continue to glow for a certain time. In our case this delay is about 7 seconds. If you
use different values for R1 and C1, you can also accomplish longer delay times. Use it for example, to set up
a stair lighting solution.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.203.
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...
