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

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---------------Little information about Video------------------
contact less AC mains voltage detector circuit which can be used to detect presence of AC mains voltage without any electrical contact with the conductor carrying AC current/voltage. Thus it can be used to detect mains AC voltage without removing the insulation from the conductor. Just take it in the vicinity of the conductor and it would detect presence of AC voltage.
This is a circuit for an AC mains voltage detector that has an insulated sensing probe of length between 5 cm to 10 cm.

[@Nematics_Lab]

*Correction* output of second stage will be 50mA and so on :)

[@imacenaveen]

I made this, works great.

[@electronic7979]

Helpful video

[@theproud77]

Cool project!

[@7bits.e]

very easy explanation ...

[@Crazytesseract]

Please clarify again. I think the current amplification from the first two transistors is needed to turn on the last transistor (ie connected to base). This current does not drive the LED. Once this Tr is turned on, the current from the dc supply passes through LED

[@ChinmayDhumal]

Simple and Neat!

[@Nematics_Lab]

Sure is!

[@harikamalakarreddydarapu7410]

Very nice

[@techelectric6962]

Useful bro

[@er.kakshshah2868]

Looks cool without arduino 👍👍👌

[@muhammadaizat9668]

can check voltage inside conceal wiring in the concreate wall?

[@Nematics_Lab]

Yes

[@YATISH6969]

how much time you need to eadit your yideo

[@karthikvs4544]

is it possible to make a photointruptor?
If yes can you make a it plz

[@Nematics_Lab]

Sure

[@RohanSharma-tl9wh]

😍😍

[@javier32]

Hello sir, j have a question
Is it ok if i use a bra1015?
Thanks

[@Nematics_Lab]

Nope you need NPN transistor

[@javier32]

@@Nematics_Lab ok thanks for your advice

[@R3APER50]

This circuit does not work right for me, it will light up if i get near the antenna or touch it but seems kinda random when going to detect voltage. Seems to just amplify any noise it receives but not necessarily from any 120v source

[@sayedhussaini4894]

Can we use 5v supply?

[@Nematics_Lab]

Yes

[@ramkrushnashinde6689]

But in darling ton pair both transistors are not same....if one is pnp another should npn.... please clear it to me

[@Nematics_Lab]

Both should be same npn or pnp

[@anmolkumar6704]

That soldering iron glowing leds happens a lot!

[@Nematics_Lab]

Yeah

[@kac3514]

Yeah mostly when soldering smd leds

[@AnthonyHernandez-tg5sv]

Wow thanks a lot 👍, this is the only video I have found that explains how the circuit works and it explains it perfectly. Can you explain what the value of hfe will be for the transistor in the example (2N3904), when I look at the datasheet for it there are several values, how do I know which one will be the one to use?

[@Nematics_Lab]

Use the average value :)

[@moving.quotes]

The antenna is not a capacitor. It's more of inductor. You can see it's a coil. A coil will have inductance

[@adriengagne8339]

It is usable inductance if both ends are connected... making this "antenna" a capacitor

[@shubhamkumaryadav4060]

Hey brother , it's working but some time , when I connect battery, the led start glowing first ,why????

[@Nematics_Lab]

Random noise & maybe inrush current

[@shubhamkumaryadav4060]

@@Nematics_Lab it have any solution??

[@Nematics_Lab]

Try adding 100uf cap between VCC & gnd

[@shubhamkumaryadav4060]

@@Nematics_Lab parallel or series

[@Nematics_Lab]

Parallel to VCC & gnd

[@theproud77]

3:13 A capacitor? Doesn't it works more like a coil?

[@Nematics_Lab]

A Coil is essential a capacitor

[@anmolkumar6704]

No it doesn't work like a coil it works like a capacitor and the more surface area the more will be it's range because of increased capacitance.

[@mayROBO]

@@anmolkumar6704 I am sure you mean it works like an inductor or coil as @TheProud said.

[@zorrosigiloso5280]

@@Nematics_Labwtf? A coil is the opposite of a capacitor. A coil is not a capacitor, they are opposite in nature, like water and oil, like women and men

[@TheRishsbh]

A Darlington pair

[@YATISH6969]

I want to help you but I can't

[@vijaypawar5075]

You can

[@vijaypawar5075]

Just tell what help are you going to do him