ChrisOfBristol
Member
rogs
I have built the detector. The first part of the circuit is exactly as you describe, apart from using a 4024 instead of your 4017. The amplification is great and the circuit is stable.
It wouldn't drive the buzzer so I have added an LM386. This works fine provided it is off the stripboard on a breadboard. If I put the LM386 and the buzzer on the stripboard I get feedback.
It may be my crude circuit (as usual) can you comment on that? Maybe another low pass filter somewhere would stop it?
View attachment 69102
I have built the detector. The first part of the circuit is exactly as you describe, apart from using a 4024 instead of your 4017. The amplification is great and the circuit is stable.
It passes your test at a distance of about 1/2 metre.To get a simple idea of whether you are in the 'ball park', sensitivity wise, you can gently rub your thumb and forefinger together, directly in front of the transducer
It wouldn't drive the buzzer so I have added an LM386. This works fine provided it is off the stripboard on a breadboard. If I put the LM386 and the buzzer on the stripboard I get feedback.
It may be my crude circuit (as usual) can you comment on that? Maybe another low pass filter somewhere would stop it?
View attachment 69102
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