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Hi everyone, i am going to start a pi metal detector build with a friend who is an electronic engineer. Had our first talk today to discuss where to start. I will hopefully be learning about electonics from him as i go along. I apprechiate this is not beginner level electronics hence getting help from an engineer. Inital thoughts from him are it is something we can do using micro controlers and make it wireless in the form of the control box. I am wanting it as i have a sight in mind that is underwater and used as a crossing point for hundreds of years over an old river that isn't used anymore. I intend to post on this project as it goes along not intending it to be a quick build but have a quality end machine
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Welcome to Las Vegas with loss guaranteed. -
What do you mean by "wireless in the form of the control box" ? No cable between coil and control box? Sounds massively over-optimistic for a first project. If you just want cordless headphones, which IS a good idea, then adding that feature is not too hard.
Better to start off with one of the better kits that are available, your engineer friend will be useful there. And buy a commercial search-coil that suits it.
Another thing - radio signals don't go through water very well, especially salt water, and especially the frequency 2.4GHz.Comment
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Thank you for your replies. I dont need the control box to go under the water as it is around 2 feet deep fresh water. I am working on the project with a friend who loves project and has over 30 year experiance in electronics working in varied specialities so not worried about his competence and ability. Was looking at getting a commercial coil and then making one to see the differece. Wireless headphones are hopefully part of the set up.Comment
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The simplest way to achieve cordless headphones is to buy one of those 87 - 108 MHz Broadcast Band FM transmitters that are intended to be used with MP3 players, and a matching FM radio receiver. I bought one of these things for 1 U.K Pound at a car boot sale:
http://www.fuzing.com/vli/002480f752...ansmitter_668A
OK, I haven't properly tried it out, there's possibly problems like the radio transmitter interferes with the metal detector (don't put them too close), but it seems like a decent project.
You can also make a basic FM transmitter by using the guts of a 'bugging device', a one-transistor oscillator circuit. You can find circuits for these things online. Use a regulated power supply to keep the frequency stable.
One place to look for MD kits is Silverdogs site:
http://www.silverdog.co.uk/shop/index.phpComment
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There are a number of combinations that you can use with 87 - 108 MHz Broadcast Band FM transmitters and receivers, trick is not to over drive the TX audio,
most of the scanning RX's need to be retuned when you switch them off.Comment
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Can confirm skippys suggestion,
FM IS the better option !!!
Recently purchased Sony Bluetooth headphones,
And an audio Bluetooth transmitter,
70 quid later........
Many many problems encountered !!!
Mainly the delay ,
Not sure if the deus and the like do this,
But 100ms delay is enough to shift the bleep
From a target from the center of the coil to the
Edge of the coil,
And when this happens both ways it messes
With your mind !!!
Other consideration is that both the headphones
And the transmitter DON'T switch off after a
Period of time of silence.
So don't go for any that say "power saving feature".
Other point to mention is what I can only guess is
A form of sound cancellation circuitry,
They seam to pause before indicating tiny bleeps
After a short period of quiet,
So target are missed,
There one minute,
Gone the next.......
But,
DIGITAL FM transmitter (ASDA 6 quid)
DIGITAL FM radio (Argos 7.99)
Does a nice job,
Very minor background hiss,
Quite comforting really......
I know there on and working !!!
Instant response,
And yes,
The UK versions default turn on frequency
Is 87.5 Mhz which is fine,
They both do the same to match,
And it's dead there for other radio stations.
Calculated that both Tx and rx have about 40 hours
Use on 2 AAA's so that's ok then.
No interference on my whites M6 from the TX.
will say though,
Extend the TX aerial , I made an external
Rubber duck aerial,
Tx is a bit weak without it,
Many links to that mod can be found on tinternet
And Utube.
Oh,
Finally,
Don't don't don't go for anything other than
Digital tuning for both,
Like, don't use one of them nasty "scan" radios......
They drift like hell !!!
Anyways,
There's my 2 peneths worth for going wireless
Earphones.....Comment
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It is to be built i believe as a didgital interface attached to analog curuit. As i said its a project for me to learn from through an experiance electronics engineer with a lot of years experience in a lot of fields. All of your imput is aprechiated and i look forward to writing up what is happening and show pics and results as i go along.Comment
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thank you for the adviceComment
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