Metal detector dc42 improvment

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ted
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Metal detector dc42 improvment

Post by ted » Mon Dec 25, 2017 8:17 pm

I just came across an interesting CD42 metal detector project, link below
It can be significantly improved by using an audio amplifier to energise Tx coil, the TDA2030 is increasing 20 times the intensity of the electromagnetic field, using serial resonance of Ct and Tx coil.
More improvments can be done by program modifications, I know electronics not programming.
Is there some one interested join me on this improvments ?

https://github.com/dc42/arduino/blob/ma ... ematic.jpg
TDA2030; https://m.aliexpress.com/item/32814901629.html

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ahull
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Re: Metal detector dc42 improvment

Post by ahull » Tue Dec 26, 2017 8:50 am

I've not had much time to look in to metal detecting with the bluepill, however I suspect with a little effort, it would make a good "brain" for a pulse induction type metal detector.

On the subject of audio amplifiers to drive the coil, of an induction balance detector, I did wonder if one of those little class D amplifier boards might do the trick. Class D is theoretically way more efficient, which is a big consideration if operating from batteries. They are also single rail operating devices, which simplifies the power supply.

Search ebay for "DC 5V PAM8403 class D" (also PAM8406, which can drive 5W into 2 ohms at 5V) for the sort of thing I'm talking about.

Designing suitable coils would perhaps be the most problematic part of the process.

There are a couple of other threads about metal detectors on the forum, not sure how far these individuals managed to get.
I will interested to see how your idea pans out. :D
- Andy Hull -

ted
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Re: Metal detector dc42 improvment

Post by ted » Tue Dec 26, 2017 3:51 pm

The results are not a theory but actual testings, coils can be the same as in original design.
I waiting for arrival of arduino board the same as dc42 have used however STM32103 will give better results, it is much faster.

ted
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Re: Metal detector dc42 improvment

Post by ted » Tue Dec 26, 2017 6:27 pm

dc42b.jpg
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ted
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Re: Metal detector dc42 improvment

Post by ted » Tue Jan 23, 2018 11:59 am

Just , Signal generator +TDA2030+oscilloscope = 70cm range for coca cola can.
Assistance with program welcome.

Image
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coca3.jpg
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dannyf
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Re: Metal detector dc42 improvment

Post by dannyf » Tue Jan 23, 2018 1:05 pm

it depends on the range of detection desired.

for me, this approach is too complicated: as it relies on the coupling between the two coils for detection. a simpler approach is to use the coil as part of an oscillator, whose frequency changes with the presence of metal (well, most metal) near the coil. thus if you detect the frequency of the coil + metal oscillator, ...

that detection can be done by comparing the frequency vs. the internal oscillator, or xtal, .... the most interesting case is to configure the coil + metal as the main oscillator and use other oscillators onboard, like the watchdog timeout to detect frequency shift....

a lowly attiny is more than enough here.

ted
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Re: Metal detector dc42 improvment

Post by ted » Tue Jan 23, 2018 1:42 pm

My goal is detect cola can from distance 1m+, there is no problems with the coil
nulling. Mentioned method measuring frequency shift is much les sensitive than Tx-Rx detectors.

dannyf
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Re: Metal detector dc42 improvment

Post by dannyf » Tue Jan 23, 2018 3:27 pm

cola can from distance 1m+
you can help yourself by setting realistic design goals and understanding how metal detection works on some metals like aluminum.

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Pito
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Re: Metal detector dc42 improvment

Post by Pito » Tue Jan 23, 2018 5:15 pm

It depends whether the can comes from US or from Europe.. Two different alloys, I think..
Pukao Hats Cleaning Services Ltd.

ted
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Re: Metal detector dc42 improvment

Post by ted » Tue Jan 23, 2018 6:09 pm

Hi Pito it is nice to see you here
On the can it says - Canada. I ordered ATmega328P on Aliexpress with it I am expecting 1m, only 30 cm more. With STM32 would be better but there is need to convert the code from AVR to ARM.

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