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4040 Mobile Phone Electromagnetic Radiation Demonstration Experiment Circuit

Source: InternetPublisher:黄土马家 Keywords: Electromagnetic Radiation Updated: 2024/10/25

Mobile phones radiate electromagnetic waves when in use. Especially GSM mobile phones, the radiation signal is stronger. This circuit can demonstrate the electromagnetic radiation of mobile phones when in use.

1. Circuit Introduction

The circuit diagram is shown in the figure below. The circuit consists of four parts: mobile phone signal reception and shaping, pulse counting and display, automatic clearing, and sound reminder.

2. Circuit Analysis

The high-frequency transistor T1 amplifies and detects the electromagnetic radiation signal of the mobile phone received by the antenna, and then outputs it to the shaping circuit composed of CD4069 to become a pulse signal, which is output to the 4040 counter. T1 is preferably a high-frequency tube C3355. 9018 can also be used. The stability of the transistor working point is provided by the DC feedback resistors R1 and R2; in order to ensure the amplification factor, the capacitor C2 bypasses the AC component in the feedback signal. The detected mobile phone signal is amplified by the linear amplifier circuit composed of the non-gate 1 of 4069.

When no electromagnetic radiation signal from a mobile phone is received, the 11th pin of the 4069 NOT gate 2 is controlled by resistors R6 and R7. It is at a high level; after two-stage NOT gate conversion, the 8th pin of the NOT gate 3 outputs a high level. The 4040 counter CR reset terminal is controlled by the pull-up resistor R8 and is at a high level, so all the outputs of the counter are zero, and the LEDs showing the binary counting results are all off. Once the electromagnetic radiation signal from a mobile phone is received.

The mobile phone signal detected by transistor T1 is input to NOT gate 1. After shaping, the pulse signal is input to the 4040 counter by NOT gate 3: at the same time, diode D1 is turned on and outputs a low level, causing the reset terminal potential to be low, the counter starts working, and the light-emitting diode lights up; at the same time, the buzzer emits intermittent beeps. The driving signal of the sound reminder is output from the Q5 terminal of the counter, and then rectified by diode D2 to drive transistor T2. It can make the single-tone active buzzer emit a "beep-beep-beep" sound with a period of about half a second.

When the electromagnetic radiation signal of the mobile phone disappears, the output of NOT gate 3 is high. The diode D1 is not conducting; the potential of the CR terminal of 4040 is controlled by R8 and C5, and becomes high after 1 second, and the counter of 4040 is cleared.

Not all of the 12 outputs of 4040 are necessarily used, but they must be used starting from the lowest bits, usually no less than 8 bits.

The power supply can be 4.5~6V, and the circuit can work without adjustment if it is assembled correctly.

The antenna is made in a special way. You only need to connect the base of T1 to ground with a 0.01u capacitor with a lead several millimeters long. That is to say, whether you plug this circuit into a breadboard or solder it on a printed circuit board, you don't need to install an additional "antenna" - the capacitor C1 itself is the antenna.

3. Demonstration experiment of electromagnetic radiation from mobile phones

(1) The detection distance experiment of this mobile phone electromagnetic radiation demonstrator is to place a mobile phone about 1m away from the device and make a call to observe. By changing the distance between the device and the mobile phone, the maximum detection distance of the device can be determined. The radiation intensity of each mobile phone is different: depending on the usage environment, the intensity of the electromagnetic signal radiated by a mobile phone is also different; the detection sensitivity of this device for GSM mobile phones is about 5m.

(2) Comparative experiment on radiation intensity of various mobile phones

There are GSM, CDMA, 3G and other mobile phone models. Which type of mobile phone has the strongest electromagnetic radiation? Through experiments, it is known that the radiation intensity of GSM mobile phones is the strongest. But on the other hand, CDMA mobile phones do not have the effect of saving power. This shows that GSM mobile phones emit pulse signals when working, with high instantaneous power; their average power is not much different from that of CDMA mobile phones.

(3) Radiation experiment of receiving text messages by mobile phone

Experiments have shown that mobile phones also emit electromagnetic signals when receiving short messages.

(4) Electromagnetic radiation test when the mobile phone is turned off

When you shut down your phone according to the program, you will find that electromagnetic radiation is generated at the same time. This is the mobile phone sending a message to the base station that it is shutting down.


4040 Mobile Phone Electromagnetic Radiation Demonstration Experiment Circuit


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