SIGNAL LEVEL INDICATOR LED FOR METAL DETECTOR

Here you find how to make a classic LED bar (strip) voltmeter without using any microcircuits and MK. It turned out to be quite successful. The circuit consists of several electronic elements, which everyone has in the bins. Further, the electrical circuit of the simplest voltage indicator in the form of a LED bar.

Schematic diagram of LED-V-meter

If you wish, you can add a small modification in the form of a transistor and a resistor – this will lead to the simultaneous extinguishment of all LEDs when the input signal level decreases, and not to a smooth linear decrease when turned off.

With the addition of one more transistor in the input circuit, everything immediately goes out and even if the capacitor held the load, the voltage on the LEDs disappears.

Transistors here are any NPN, LEDs for example LL4148. Or special LED assemblies in different colors.

The board is LUT, except for the capacitor and the LED, everything is in SMD form.

You can add an amplification stage – the larger it is, the higher the voltage on the capacitor will turn out, the more current the transistor takes from it, but this also gives non-linearity.

Items are subject to change. For example R 22k and C 10uF affect the rate of light of the ruler. This light bar is perfect, for example, for measuring the voltage of a power supply unit, battery or as a control level indicator.

Reference: https://radioskot.ru/