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.
Содержание ELECTRONICS EXPERIMENTS BOX
Страница 4: ......
Страница 251: ...253 Fig 3 27 Circuit 27 4 seconds switch off delay Fig 3 28 Circuit 28 20 seconds switch off delay...
Страница 258: ...260 Fig 3 42 Circuit 42 Active 8 5V battery monitor Fig 3 43 Circuit 43 Active 7 8V battery monitor...
Страница 260: ...262 Fig 3 46 Circuit 46 Meters for 1 5 V Zener diodes and higher Fig 3 47 Circuit 47 Discreet 2 2V Zener diode...
Страница 261: ...263 Fig 3 48 Circuit 48 Discreet 2 9V Zener diode Fig 3 49 Circuit 49 Discreet 3 7V Zener diode...
Страница 265: ...267 Fig 3 56 Cir cuit 56 Audio limiter Fig 3 57 Circuit 57 Amplifier for a storm detector...
Страница 269: ...271 Fig 3 64 Circuit 64 Stabilizer for 1 9 V Fig 3 65 Circuit 65 Stabilizer for 2 5 V...
Страница 275: ...277 Fig 3 80 Circuit 80 Quiztimer 30 seconds Fig 3 81 Circuit 81 Handy diode tester...
Страница 290: ...292 Fig 3 118 Circuit 118 HF watch dog with LED indicator Fig 3 119 Circuit 119 HF watchdog with moving coil instrument...
Страница 295: ...297 Fig 3 130 Circuit 130 4 seconds switch on delay Fig 3 131 Circuit 131 15 seconds switch off delay...
Страница 298: ...300 Fig 3 136 Circuit 136 NAND gate with moving coil instrument Fig 3 137 Circuit 137 Input level Mixing console...
Страница 300: ...302 Fig 3 140 Circuit 140 Electrometer with moving coil instrument Fig 3 141 Circuit 141 Simple AM Radio...
Страница 315: ...317 Fig 3 179 Circuit 179 HF generator 150 kHz Fig 3 180 Circuit 180 HF generator 420 kHz...
Страница 324: ...326 Fig 3 202 Circuit 202 3 seconds switch on delay Fig 3 203 Circuit 203 7 seconds switch on delay...
Страница 325: ...327 Fig 3 204 Circuit 204 Piercing siren sound with Piezo element Fig 3 205 Circuit 205 Discrete Operational ampli fier...
Страница 328: ...330 Fig 3 210 Circuit 210 Discreet 5 2V Zener diode Fig 3 211 Circuit 211 Discreet 7 4V Zener diode...
