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steven

ghost detector circuit, 3 volts buzzer adition

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:) im a bit stuck on this one can someone include a 3 volts buzzer in this circuit si it not just flashes an led but sounds a buzzer , this circiut responds very welll to lightening bolt flashes so i just need to know how to add a tiny buzzer to it

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The circuit would be easier to understand if proper op-amp symbols were used rather than just a box.

I don't know how it works and am not going to redraw it with the proper op-amp symbols so I can figure it out.

I assume you could connect a small piezo buzzer across the LED and its limiting resistor.

Hang on a second this circuit will not work: there's no power supply and an the LM324 won't be able to drive an LED properly from a 3V supply because it has too higher saturation loss 1V, meaning the LED will be very dim if you're lucky.

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:) look carefully theres the neg and pos inputs im runing 2 of these circuits each off a nine volts battery no problems at all , the led is the 5mm one,  i think its voltage is 1.7 ill recheck that  soon to make sure its right
the led blinks to each flash of lightening and aint dim but i was so suprized  at how good it works . thankyou for youe input anyhow  and i find it awkward with the tryangle ic symbols as they aint even rectangle like the real thing ,  i was lucky to find that circuit on the net so when i made a printed circuit board version of it it was better to follow with the proper ic  shape configuration but then the resistor tracks are a bit  awekward to but i got it  ok

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:) look carefully theres the neg and pos inputs

All right, I missed that.

im runing 2 of these circuits each off a nine volts battery no problems at all ,


Why did you say 3V?

the led is the 5mm one,  i think its voltage is 1.7 ill recheck that  soon to make sure its right

That sounds about right for a red LED.

The reason why it will work from a 9V supply but not from a 3V supply is that the op-amp has a typical saturation loss of 1V at 10mA, leaving only a fraction of a volt across the resistor so LED will be very dim and won't light when the battery discharges a bit.

the led blinks to each flash of lightening and aint dim but i was so suprized  at how good it works . thankyou for youe input anyhow  and i find it awkward with the tryangle ic symbols as they aint even rectangle like the real thing , 

The correct spelling is triangle and it doesn't matter how the real thing looks, it's a schematic and isn't supposed to look like the finished circuit. All the other symbols, transistor, LED, resistor etc. look nothing like the real components, the symbols were chosen because they're concise and easy to draw.

The fact that it's a triangle box doesn't really matter, it could be a square box with a +, - symbol to denote the non-inverting and inverting inputs respectively and an O for output and I would understand it perfectly. The same is true for logic gates, for example a 14 pin box means nothing but four individual NAND gates with the connections shown, is easy to understand.

Using a separate symbol for each op-amp makes the circuit easy to understand because one can easily see how each op-amp is configured, i.e. inverting amplifier, non-inverting amplifier, Schmitt trigger oscillator etc.

i was lucky to find that circuit on the net so when i made a printed circuit board version of it it was better to follow with the proper ic  shape configuration but then the resistor tracks are a bit  awekward to but i got it  ok


Once you've drawn the circuit correctly, it's time to do another drawing to help you to transfer it to a PCB. I normally just put pin numbers on the symbols and tick them off after I've made each connection, then I check again and again before I make the PCB.

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:)3 volts is the tiny buzzer voltage minimiun 3 volts the circuit runs on 9 volts  ive just tried an idea i removed the 47r resistor and put a tinned coper wire link of unknown resistance in its place and put the buzzer after it in place of the led and it works , not to high not to low sounding just ok for me

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I'm glad it worked and hope your 3V buzzer won't be damaged when run at near 9V for long periods of time.

Have you measured the votlage across the buzzer? It's possible the op-amp's internla resistance is lowering the voltage, it certainly won't be 9V, probably 8V at most bue could be lower.

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:)the minimiun voltage for the buzzer is 3 volts the maximiun is 30 volts  i got another problem now  the circuit seems to trigger to easy now and when i sit it somewhere where it aint getting triggerd it will stay silent for so long then the buzzer will go of and keep going and wont stop unlless i pick it up with my hands and or turn it off  the recamendations from the sight i biult the circiut from was to try the buzzer in sieries with the led and they said this may help stop the problem of it sounding continiuosly but the resister in it  and led lower, the voltage and current ,enough and if i put the buzzer in sieries it may drop out of the threshold limit for the buzzer to trigger with 3 volts minimiun  and i would end up with a buzzer that barley sounds.
i did test the buzzer in place of the led but it sounded just barely  so maybe i would have to restore it back to just the led for the time being.

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:)the minimiun voltage for the buzzer is 3 volts the maximiun is 30 volts 

Why didn't you say so before? The more information you give, the better,

i got another problem now  the circuit seems to trigger to easy now and when i sit it somewhere where it aint getting triggerd it will stay silent for so long then the buzzer will go of and keep going and wont stop unlless i pick it up with my hands and or turn it off  the recamendations from the sight i biult the circiut from was to try the buzzer in sieries with the led and they said this may help stop the problem of it sounding continiuosly but the resister in it  and led lower, the voltage and current ,enough and if i put the buzzer in sieries it may drop out of the threshold limit for the buzzer to trigger with 3 volts minimiun  and i would end up with a buzzer that barley sounds.
i did test the buzzer in place of the led but it sounded just barely  so maybe i would have to restore it back to just the led for the time being.


From what you've said, it seems like it's working.

There's probably a way to adjust the sensitivity and one of the resistors probably needs to be a pot.

If you convert it into a readable schematic by drawing it with proper op-amp symbols laid out clearly, I might be able to show you how to alter the sensitivity.

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:)theres nothing wrong with the spelling except maybe one word recamendations but i think that looks ok its just a confuseing line in what ive said that is confuseing but the spelling is ok  and spelling checker dosent work here iether, america has words there that are spelt differently  so as long as its readable you can handle it , over here and other countrys we call our mothers mum in america yous call ya mothers mom see the difference,  in spelling. i  see audio guru you sure get around, when i go looking for circuits and ideas i often see your name in a site and allso hotwater wizard to yous must have the lead in the most electronic sites membership. ps you spelt english wrong ha ha ha lol

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There's a lot wrong with your spelling, look at what you've just posted, there are at least three misspelt words: confuseing, countrys,  iether and probably more.

Duh, audioguru deliberately misspelt the word English - any fool can see that.

Seriously though, you would get more help if you used a spell checker, Firefox comes with one built-in or you can copy and paste from a word processor.

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