Magnetic field detection circuit

This article introduces a magnetic field detection circuit, as shown in the figure below. The L1 in the figure is a 110V (220V can also be used) AC relay coil, the coil L1 acts as a magnetic field sensor. Integrated block IC1 is a comparator LM339, and LED1 is a detection indicator. The magnetic field detection circuit composed of these components in the above figure has a very high detection sensitivity. Even if a small permanent magnet moves near L1, the LED will respond (light up) immediately.

In the normal condition of the circuit, that is, there is no iron-containing material near L1, there is no potential difference between the two ends of the inductor L1, that is, the two pins of IC1, and the circuit does not work. As long as there is a change in the magnetic field near L1 (if any The presence of iron material), L1 will generate a tiny AC signal, causing a potential difference between the two comparison terminals of the comparator. As a result, there will be a high and low level change at its output terminal, and the LED will flash (LED on and off ) To indicate the presence of iron-containing substances near L1. Therefore, the magnetic field detection circuit can be used to find iron-containing objects on the ground.

For example, change L1 in the circuit above to an electromagnetic microammeter head (for example, 50μA), it can become a vibration sensor, as shown in the following figure. If there is a small vibration outside, LED1 can display it.

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