[quentinuys]

Hi Everyone.

I really need your help..

I have made the Matchless Metal Detector that you can find here. www.geotech1.com/pages/metdet/projects/matchless/matchless300c.pdf

I have put everything together as in the pdf instructions but just cant get the locater to produce the beat frequency over the piezo. There are a very light tone if you hold the piezo against your ear but thats it.

I included a diagram with the voltage readings across my board. I also attached some images of my board. I know you will spot my error just looking at it. Thank you again.



Here are the voltage rating over different parts of the diagram


Here are my board. As you can see I am a beginner in electronics. I also only have a standard multimeter so I cant test Induction (mH etc) or current.

[Barney]

The voltage you show to drive the piezo speaker is too low - was that measured with a strong target signal?  Have you tried normal head phones?