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Hi , I'm trying to make a vlf metal detector. I see the 8khz signal I produce in the tx and rx coils, the coils are in proper alignment. I reset the oscillation, but the oscillation does not move in metal detection. Where am I making a mistake? When I bring the RX coil closer to the TX, I turn on the LED. Frequency transmission also occurs. No detection on metal.
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A metal target will not normally change the TX signal in any noticeable way. With an IB coil the RX signal should be nearly zero and a large metal target will make a noticeable RX signal at the preamp. To see smaller targets, you need to look at the demod signals. -
I'm trying to increase the rx signal TL072 but it doesn't work. Is it necessary to rectify the rx signal? Do I need to wrap the coils in aluminum foil?Comment
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No and no. Maybe show us your circuit diagram and coil design. Are you able to measure the TX signal, and is the RX signal (no target) near zero?Comment
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Yes, I measure my TX signal. When I put the coils on top of each other, I see the TX signal in the RX coil. Then, when I put the coils in the middle, I reset the oscillation. I start testing, but when I approach a metal object, the RX does not oscillate. Is there a circuit to amplify the RX signal?Comment
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It is very difficult to see a target signal just looking at the raw RX coil voltage. You will need a amplifier. I suggest you look at a Tesoro schematic like the TGSL or Bandido. Do a forum search for those.Comment
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Thank you adminComment
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Can you give an example circuit to amplify the RX signal?Comment
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A simple non-inverting opamp with a gain of 100 would be a good start.Comment
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Is it difficult to find it yourself... religion does not allow it? Especially since you were told which models to look at.Originally posted by sifirzeri View PostComment
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