The mobile phone radiates electromagnetic waves outward during use. Especially for GSM mobile phones, the radiation signal is stronger. This circuit can demonstrate the electromagnetic radiation conditions of the mobile phone during use.
1. Circuit introduction circuit diagram The circuit shown in the following figure consists of four parts: mobile phone signal receiving and shaping, pulse counting and display, automatic clearing, and sound reminder.
2. The circuit analysis high-frequency triode T1 amplifies and detects the electromagnetic radiation signal of the mobile phone received by the antenna, and then outputs to the shaping circuit composed of CD4069 to become a pulse signal, which is output to the 4040 counter. T1 should use high frequency tube C3355. It is also possible to use 9018. The stability of the triode operating point is provided by DC feedback resistors R1, R2; to ensure amplification, capacitor C2 bypasses the AC component of the feedback signal. The detected cell phone signal is amplified by a linear amplifying circuit composed of the non-gate 1 of the CD4069.
When the electromagnetic radiation signal of the mobile phone is not received, the 11 pin of CD4069 non-gate 2 is controlled by resistors R6 and R7. Is high; after two levels of non-gate conversion. The 8-pin output of the non-gate 3 is high. The CD4040 counter CR clear terminal is controlled by the pull-up resistor R8, which is high level, so all the outputs of the counter are zero, and the LEDs showing the binary counting result are all off. Once the mobile phone electromagnetic radiation signal is received.
The cell phone signal detected by the transistor T1 is input to the non-gate 1. After shaping, the pulse signal is input from the NOT gate 3 to the CD4040 counter: at the same time, the diode D1 is turned on and outputs a low level, which causes the zero terminal potential to be low, the counter starts to work, and the LED is lit; meanwhile, the buzzer emits Intermittent barking. The drive signal for the sound reminder is output from the Q5 terminal of the counter, and then rectified by the diode D2 to push the transistor T2. The monophonic active buzzer can be made to emit a "one-on-one" sound for a period of about half a second.
When the electromagnetic radiation signal of the mobile phone disappears, the non-gate 3 outputs a high level. Diode D1 is not conducting; the CR terminal potential of CD4040 is controlled by R8 and C5. After 1 second, it goes high and the CD4040 counter is cleared.
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The 12 outputs of the CD4040 are not necessarily used. But you must start with the low position, generally no less than 8 places.
The power supply can be used from 4.5 to 6V, and the circuit assembly can be operated without any adjustment.
The antenna is made in a special way. Just ground the base of the T1 directly with a 0.01u capacitor with a few millimeters of long leads: that is, plug the circuit on the breadboard. Still soldering on a printed circuit board, there is no need to install an additional "antenna" - the capacitor C1 itself is the antenna.
3. Mobile phone electromagnetic radiation demonstration experiment
(1) The mobile phone electromagnetic radiation demonstrator detection distance experiment put a mobile phone placed about 1m away from the local machine, dial the mobile phone for observation; change the distance between the work and the mobile phone to determine the maximum detection distance of the work. The radiation intensity of each mobile phone is different: the intensity of a mobile phone radiating electromagnetic signal is different depending on the environment used; the sensitivity of this work to the GSM mobile phone is about 5m.
(2) Comparison of radiation intensity of various types of mobile phones The experimental mobile phone system has GSM, CDMA, 3G, etc. Which type of mobile phone has large electromagnetic radiation? It can be seen from experiments that the GSM mobile phone has the highest radiation intensity. But on the other hand, CDMA mobile phones do not have the effect of saving electricity. This shows that the GSM mobile phone emits a pulse signal when it works, and the instantaneous power is large; its average power is not much different from that of CDMA mobile phones.
(3) The mobile phone receives the SMS radiation experiment. It can be known that the mobile phone also emits electromagnetic signals when receiving short messages.
(4) Electromagnetic radiation experiment when the mobile phone is turned off The mobile phone is shut down according to the program, and it will be found that electromagnetic radiation is generated at the same time of shutdown. This is the information that the mobile phone sends its own machine to the base station.
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