Simple circuit checkover

Juan's picture

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Simple circuit checkover
January 3, 2021 - 7:47am

Can someone please look over this circuit and see if it's workable.

It is supposed to detect a loud sound and then turn the relay on for a few seconds then turn off .

When I figure out how to post an image that is .

Juan's picture

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sound relay mods - Copy.png

Sourav Gupta's picture

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Yes it supposed to work. You can test it with breadboarding.

Juan's picture

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Thanks for the  reply . I have been tasting it and so far it don't work  but I have made two changes that have not been tested yet .  I will give it another try . 

I am beginning  to think I may have a faulty breadboard . 

Sourav Gupta's picture

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Juan's picture

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Thanks for the help but that circuit just creates a new set of problems .  Can it drive  the relay coil from tthe IC and how do I interface the relay , and also I have to buy new parts .  I am trying to stay away fron IC circuits because it makes a PC board much harder to make at home . 

Michal Podmanický's picture

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Your circuit should work.

The possible problem can be the 3M3 resistor does not open the T1 if u use a T1 with low Hfe (try BC547c - Hfe at least 300).

Another problem is the lenght of time to relay stays powered ON - it will depends on sound loudness and time lenght of sound.

According to my opinion, I would use a simple 2 transistor Monostable multivibrator triggered by MIC - this propose will guarantee you a constatnt relay ON time.

 

Juan's picture

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Thanks Michal , I will try and find another transistor for T1 . As far as I can tell the electro capacitor C2 is a timing cap and  turns the circuit on when it's discharged .

It is supposed to come on as soon as you connect power then after a few seconds turn the relay off , then wait for a sound  to turn back on .

Don't ask me how that works .  If you can post a circuit and how it interfaces I might try it but no IC 's please . 

Michal Podmanický's picture

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I would do it this way:

 

Michal Podmanický's picture

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Michal Podmanický's picture

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It is a draft only, you must find the right values of components, maybe rebuild the MIC part.

Juan's picture

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Thanks for the effort  but  again that's just a whole new set of unknowns .