How to make voltage detector

[johnsri]

Hello
How to make voltage detector and current detector circuit

 

[ZipZapOuch]

Hello
How to make voltage detector and current detector circuit

That should work quite well. Looks like a Forrest Mimms design.

How to make AC Tester | Mains Voltage Detector Circuit | DIY -

In this tutorial we are going to make this simple 3 Transistor contact less Mains voltage detector circuit. And understand how it works.

nematicslab.com

 

[Karklebapper]

What do you want your circuit to do? Please be as specific and detailed as possible. Why not buy a digital multimeter for $10 - $20? The circuit you show will exhibit high current gain, but it might even drive the LED and buzzer when there is nothing that you would consider to be detectable.

 

[ZipZapOuch]

What do you want your circuit to do? Please be as specific and detailed as possible. Why not buy a digital multimeter for $10 - $20? The circuit you show will exhibit high current gain, but it might even drive the LED and buzzer when there is nothing that you would consider to be detectable.

If built right, it works well sensing a mains voltage source from a few inches. Designed by Forrest Mimms in the 1970s.