Small Metal Detector II

Posted on May 22, 2012

A Simple design based on a CS209A IC that can give surprising results and draws very little current from a 9 volt battery. It worked good on the Bench, But not so good outside for general metal detecting. But Definately a good design for detecting studs in a wall, with the right coil! This particular circuit was built so it can be used with an LED and Buzzer or just the LED or just the Buzzer. Battery voltage can be up to 20 volts, but it doesn't add to the sensitivity. In Addition, Changes to the Potentiometer value can be made, adding a smaller pot in series to make a more sensitive trip point.

Small Metal Detector II
Click here to download the full size of the above Circuit.

This circuit operates on the principal of changes in "Q" of the coil. So it is important to try and make a High Q coil! But I found that even simple coils gave fairly good results! It is recommended to use "Litz" Wire, But I just used vinal covered wire on one and also another with magnet wire and I got pretty good results with both coils. Having now put a board together and a few tests outside, it appears the coil needs a Faraday Shield. Unfortunately, Litz Wire is hard to find, but it does help! Additionally a coil wound on a "Power Ferrite Rod" can give good sensitivity as well as abn Accurate Pin-pointing effect of metal objects! I obtained Free Samples of the chip from "On Semiconductor", but unfortunately most of you will have to buy it. Etched and drilled PCB's are available for $3.00 ea. US Funds, Plus a Postage cost of $1.00. But this is NOT SUITABLE for the Surface Mount Package. I can No Longer Supply the CS209 It is available from Some Sources, But only in the Surface Mount Package, And with a Minimum Order of 100 Pieces.

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