143
2.54 Sensitive RF watchdog
Circuit 118:
RF watchdog with LED indicator
Setup information
Install the two transistors, the two diodes, the eight resistors and the three ceramic capacitors as shown in
Fig. 2.118
Finally, insert the ten jumper wires. Check the placement on the board and only then connect the
battery.
Components required:
1 x 2N3904 transistor,
1 x 2N3906 transistor,
1 x BAT 85 Schottky diode,
1 x red LED, 4 x 1 k
Ω
resis-
tors, 1 x 2.2 k
Ω
resistor,
1 x 4.7 k
Ω
resistor,
2 x 10 k
Ω
resistors,
1 x 10 nF ceramic capaci-
tor, 2 x 100 nF ceramic
capacitors, 1 x breadboard,
1 x battery, 9V battery with
clip connector
Fig. 2.118:
RF watchdog with
LED indicator
Experiment
You cannot smell electromagnetic radiation. Use this circuit to detect it within the range of 100 kHz to 1 GHz.
Normally, the red LED is not on or only dimly lit. As soon as radio waves are received, the LED turns on
brightly. The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.118.
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...
