Handheld-MD to Groundsearch Mod

[Funfinder]

This is my newest invention - the producers should extend
their Security-MDs as default with such a very useful hole.

Upper side the diamter is around 1cm and down ca. 7mm.

You can use a simple ski-stick or a tripod telescopic-bar or so.
There exist much more lightweight solutions than ski-sticks.

This mod is simple:

Find a useable stick with bendable and slightly conical tip
so it will tight fit into the MDs hole you have to create.

Open the MD and look for a place where you can melt 2 holes
with the soldering-iron without damaging cables or the pcb.

Search for a short conical tube made out of gum or rubber or
soft-plastic or create something like this from all kind of stuff.

My tube was made from a rubber kind object of the ski-stick
and connected by soldering and mixing both plastics at the
upper side of the detector. The bottom end of the tube was
left unfixed for further possibilities to open the detector.

This is the absolute lightweight solution and for taking a
MD even to otherwise not possible sites or locations!
And the cost of around 15-50 bucks is riskless if you
have to however leave behind your equipment.


Those handheld-MDs have different detection-depths
but most of them are good enough for ground search.
Of course there is no disc or ground balance but the
size and weight is unbeatable, you can make your
kids happy with such a cool treasure-hunting-toy
and for some occasions such a MD is: "priceless".


mini nail: 5cm
coin: 7.5cm (3'')
digicam: 10cm
middle cooking pot: 25cm (10'')
maximum: ca. 40cm (over 1 ft)

[wam]

By the way, how it works? It has two windings - TX and RX but both have the same size.
Does some one know the theory of it?

[Funfinder]

Thx for your interest.

Probably there are different types of used ciruits.

The one I have is "signal while moving near metal" only
and I guess it has a very simple integrated circuit solution
where the IC compares emfield energy/loss of the both coils.

It needs just a few milliwatt of the 9V for the field-strenght
over the 12.5cm / 5'' coil and has no DD configuration -
otherwise the sensitivity could be alot improved.

[wam]

MD-300

Hi, this is what You get for $17.00 with free delivery from HongKong on Ebay
It can detect fridge from more then 50 cm if sensetiviti pot retuned.

[gregor]

Refreshing this thread. I bought this metal detector just for playing and although it is a very cheap detector I found its performance quite impressive, but I would like to improve something. This detector is very sensitive to power supply parameters, I have to readjust the sensitity pot as the battery life runs out. Another thing is that this detector gets many false signals. I am thinking about stiffening and shielding of the search coil to eliminate false signals, but is it possible for this type of coil?. I would also like to change something with the battery pover supply to make it more stable for longer. I would appreciate your opinions and suggestions. Thanks

[Davor]

Shielding will make sense if you can attach it to some ground connection within the device. you must leave a gap in shielding so that it does not become a short circuit. Stiffening will make sense if you notice it is triggered by vibration. A few drops of crazy glue will fix that.
As for batteries ... seek alkaline. All the better solutions are more complex and require external power.

[Funfinder]

Not all those models use the same circuits or coils.
You could add a little circuit that stabilized the battery output
- of course to a bit lower voltage than 9V.

Or as simple solution:
You can use 2 good quality alkaline batteries in parallel
for more and longer voltage stability.

And don't set the variable resistor at a too critical border
sensitivity position if the instability isn't worth it.

[gregor]

I found shielding very difficult since the coil is glued to the case - shielding is possible but coil has to be made anew. Stiffening - no problem. Using this detector in vibration mode makes battery life much shorter than in sound mode. I simply removed the vibration motor, indication by led is still working fine then and is very useful when discretion is required.
Generally not a bad detector for playing but needs a little patience from user. Now thinking about buying another one just to make use of housing case for placing static type of metal detector circuit inside.

[satdaveuk]

Hi, this is what You get for $17.00 with free delivery from HongKong on Ebay
It can detect fridge from more then 50 cm if sensetiviti pot retuned.

Note the 3 connections on the left hand side feeding the coil, looks centre tapped unless my eyes are deceiving me.

[satdaveuk]

Ive just ordered one to play with from china £7.42 incl p/p, the parts would be double that proberly.
Im thinking maybe moding to make pinpointer, its got the vibro/light and sounder, perfect for the job at know extra exspense
If inductance is measured correctly maybe make a smaller coil on a form out of the same wire if not glued as Gregors was, then add regulator, maybe 8v if it will run on it to give it stability, and then if success could resell them as MD pinpointers at say £40 . Bargain, yellow people watch this space lol
Thats my plan anyway.

Regards

Dave

[Funfinder]

I found shielding very difficult since the coil is glued to the case - shielding is possible but coil has to be made anew. Stiffening - no problem. Using this detector in vibration mode makes battery life much shorter than in sound mode. I simply removed the vibration motor, indication by led is still working fine then and is very useful when discretion is required.
Generally not a bad detector for playing but needs a little patience from user. Now thinking about buying another one just to make use of housing case for placing static type of metal detector circuit inside.

Try to create a ferrite rod for pinpointer or a thick 3cm coil
and tell us how it works.