Good afternoon to all,

May I ask for help in improving this circuit? The function is that it will beep 5 times when the switch is pressed but there are times that the buzzer will beep immediately without pressing the switch yet.

Any suggestions are welcome and thank you.

 

hi Crea,
Is this homework or just a self build project.?
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hi Crea,
Is this homework or just a self build project.?
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Hello,
It is the latter sir. My apologies if this is the wrong section to post. You may delete or move this thread. Thanks.

 

hi,
No problem, will move it for you.
On your circuit add a 100uF and 100nF capacitor on the 12v supply lines to the 555.
Lets know how it goes.
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hi,
No problem, will move it for you.
On your circuit add a 100uF and 100nF capacitor on the 12v supply lines to the 555.
Lets know how it goes.
E

Thank you for the suggestion. Please see attached picture, is it the correct position to put the capacitors?

Thanks again.

 

hi,
The two caps are in parallel across 12V to 0V.
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Update:
Electrical noise on the 12V rail can cause erratic triggering of the 555.
The purpose of the caps is to reduce the electrical noise on the rails to a level that does not cause a false trigger.

 

Thank you sir. I will update you once I have tried this.

 

Update:
Electrical noise on the 12V rail can cause erratic triggering of the 555.
The purpose of the caps is to reduce the electrical noise on the rails to a level that does not cause a false trigger.

Sir may I ask why two capacitors in parallel instead of 1? Curiosity speaks if you don't mind. Thanks a lot.

 

hi,
The higher value cap, 100uF can supply current to the 555, if the 12v drops momentarily.
The lower cap 100nF has a lower impedance at higher frequencies than the 100uF, so 'electrical noise' , fast spikes on the 12v are shunted to 0v/gnd.

Thats a very basic explanation, if you want to know in greater detail, ask.?

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hi,
Thats a very basic explanation, if you want to know in greater detail, ask.?

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Yes please do explain more. thanks.

 

hi,
OK, Look thru this thread that discusses capacitors.
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https://forum.allaboutcircuits.com/...apacitors-instead-of-one.152209/#post-1306316

@danadak