I’m gonna show you how to make a really simple ac voltage detector. So let’s have a look at how I made this.
The components for this project are:
3 pcs BC547 transistor,
1 pc 1M ohm resistor,
1 pc 100k ohm resistor,
1 pc 220 ohm resistor,
a 9V battery clip, and a 9V battery.
Now let’s see at the transistor. The left pin is the collector, the middle pin is the base, and the right pin is the emitter.
1. The connection goes like this: the emitter pin of the first transistor is connected to the base pin of the second transistor, and the emitter pin of the second transistor is connected to the base pin of the third transistor.
2. The first transistor is connected to the 1M ohm resistor, the second transistor is connected to the 100k ohm resistor, and the third transistor is connected to the 220 ohm resistor.
3. Then, connect the 1M ohm resistor to the 100k ohm resistor. And then connect the 100k ohm resistor to the cathode leg of the LED, and the 220 ohm resistor, we connect it to the anode leg of the led.
4. Finally connect the positive wire of the 9V battery clip to the anode leg of the led and the negative wire to the base of the third transistor, and the antenna to the to the base leg of the first transistor.
5. And that’s it, we are done!
Just remember don,t touch the 3 transistor and the antenna.