Electromagnetic radiation monitor

When you work at a computer (PC) or watch TV, your body is immersed in the radiation field generated by electronic devices, such as pulsed electromagnetic radiation (PEMR) generated when electrons scan line by line on the display screen of a cathode ray tube (CRT) monitor. These radiations have low frequencies and belong to extremely low frequency energy.

These artificially generated electromagnetic radiations can destroy the biomagnetic field of the human body. In the biomagnetic field, the impact of thousands of electrons can affect the vitality of human cells. If the human body is exposed to pulsed electromagnetic radiation fields for a long time, it will change the cycle of the human body's hormonal biological order, thereby causing changes in human emotions, confusion in the orientation of self-regulation, eye fatigue, depression, etc., which are often called computer complications. The closer you are to the computer, the greater the risk. Therefore, the human body must maintain a safe working distance from the computer.

The circuit in the attached figure can help you monitor the electromagnetic radiation from the monitor and display the radiation intensity with the light emitting diode LED. The radiation pulse can also be displayed in a flashing manner through LED2 to LED4.

In order to detect the radiation energy of electromagnetic waves, the circuit in the figure uses an induction coil L1 to pick up the radiation energy. L1 is a small inductor that can be replaced by the coil used in the fluorescent lamp (CFL) circuit. The two ends of L1 are directly connected to the input stage of the operational amplifier (TL071).

TL071 (IC1) is a low noise JFET operational amplifier, its input voltage can be very low. It is a low voltage input. And only 2nA offset current. The inverting input pin ② and the non-inverting input pin ③ of the operational amplifier Ic1 only need 7nA bias current.

The detection coil L1 receives the magnetic field energy radiated by various monitors when they are working, and generates a potential difference at the input end of the op amp IC1, so that the output end ⑥ outputs a high level, which lights up LED1. An adjustable resistor VR1 is connected between the ① and ⑤ pins of IC1, as a compensation regulator for the op amp.

The output pulse of Ic1 is fed into the display driver LM3915 (Ic2) through VR2. IC2 is a monolithic logarithmically calibrated driver. The internal part of this IC can logarithmically calibrate the variable input voltage for LED display. IC2's external LED2, LED3 and LED4 will light up with an input voltage increment of 125mV. Resistor R2 controls the brightness of LED2, LED3 and LED4.

When the detection coil L1 approaches the PC display, the output voltage of IC1 increases, and LED1 lights up to indicate. At the same time, the input voltage of IC2 increases. As a result, LED2 and LED3 light up in sequence. Finally, LED4 lights up. When LED4 lights up, the buzzer sounds to indicate high-intensity electromagnetic radiation. Capacitor C1 can keep the input signal of IC2 stable to ensure the intuitiveness of the indication.

During production, the detection coil is placed separately at the appropriate position in the room, and other components are mounted on the circuit board.

After installation, add +9v battery (PP3). Place coil L1 61cm away from the monitor. Adjust VR1 to make LED1 just turn off, and adjust VR2 to make LED2 just turn off. Then bring detection coil L1 close to the monitor and confirm that LED1~LED4 are all lit and the buzzer sounds. At this point, the circuit measurement is ready to monitor electromagnetic radiation.

Note: As the movement of the electron beam intensifies, the display screen will become whiter and the electromagnetic radiation will be stronger. In addition, the circuit shown will not respond to LCD monitors because the electromagnetic radiation of LCD is close to zero. In the test circuit, a +12V relay coil can replace the coil in the CFL (i.e. L1).