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Cell phone detector

daniel_33

New Member
Hi guys, I found few circuits similar to that one but I can't find any proper explanation of working of such circuit other than very very general one. I'd like to know what exactly every element does. Could anyone help me with analysing this circuit ? detektor.jpg
 

Nigel Goodwin

Super Moderator
Most Helpful Member
I don't see that circuit doing anything.
Presumably it just depends on a VERY near cellphone totally swamping the 'circuit' and causing the LED to light.

But you can't really analyse it, as it's not really a circuit - just a load of random crap.

I'm sure most (all?) people here have heard buzzing noises through their computer speakers when their phone transmits nearby - you can even hear there's an incoming call before it starts ringing :D
 

JimB

Super Moderator
Most Helpful Member
it's not really a circuit - just a load of random crap.
I agree with that!
Example, the so called "antenna" is decoupled to ground by a capacitor (actually three capacitors).

The circuit is nonsense.

JimB
 

Diver300

Well-Known Member
Most Helpful Member
If the circuit works, it is only because of the imperfections in the components. As others have pointed out, the capacitors are shorting the aerial. However, electrolytic capacitors are will have a large impedance at cell phone frequencies, so they will be more like inductors for those frequencies.

There are lots of circuits that rely on secondary characteristics of components. The Joule thief circuit is one, as it only works due to inductor saturation.
 
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It's just a basic comparator circuit with hysteresis - take out the IC symbol and replace it with the proper op-amp symbol and it all becomes clear, although one of the caps could possibly be dispensed with.
 

daniel_33

New Member
Do you think its possible to modyfiy this somehow so it would have more sense or is it in general not possible to do such circut?
 

daniel_33

New Member
Lets say I want it to light up the diode when I put my phone next to it when it is calling someone. From your answers I understand it may work just because sth is not working right but the circuit doesnt have any function itself.
 

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