141
2.53 Sensor button (finger)
Circuit 116:
On button with sensor
Setup information
Install the two transistors, the LED diode and the five resistors as shown in
Fig. 2.116.
Finally, insert the six
jumper wires. Check the placement on the board again and only then connect the battery.
Components required:
1 x J111 FET transistor,
1 x 2N3904 transistor,
1 x red LED, 1 x 1 M
Ω
resistor, 1 x 100 k
Ω
resis-
tor, 3 x 1 k
Ω
resistors,
1 x breadboard, 1 x 9V bat-
tery with clip connector
Fig. 2.116:
On button with
sensor
Experiment
Although everything is wired correctly, nothing will happen when you connect the battery; the LED remains
dark. This circuit is a responsive to a DC voltage amplifier with a high-resistance input. We use the bare end
of the wire jumper as a sensor. When you touch the sensor surface with grease-free fingers, the red LED will
shine brighter. If you use a relay instead of the LED, you could turn on your lights or the audio system with
just a tap of your finger.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.116.
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...
