Falcon MD20

[Altra]

Here are the values for the pots and trimmers. This is for the MD 8, current model is MD 20. The probe is a 3/8" ferrite core probably 20 to 40 turns of AWG 32? These must be good for something, I believe mine is from the 1980's

[DOOLEY]

ah , i see , a 386 , but then everyone will know when youve struck gold !

travel in pairs , carry a 45

[homefire]

hello all , just been reading this thread ,
the picture of the insides shows an 8 pin chip labled u1 ,
but neither schematic posted shows u1 on it ,
what is it ? why is it now shown ?

or am i been silly ?

If you read the whole thread, you will see that sense the schematic was made up, they upgraded the audio section.

Probably a LM386!

[DOOLEY]

hello all , just been reading this thread ,
the picture of the insides shows an 8 pin chip labled u1 ,
but neither schematic posted shows u1 on it ,
what is it ? why is it now shown ?

or am i been silly ?

[Tepco]

In old days, this configuration is called "ALL" or Amplitude Locked Loop. Rectifier and feedback will maintain constant oscillator amplitude at some point, loading the LC tank will change that control signal and this is detected as a target response. Probably worst way to detect metal. Very long time ago, similar circuits, but in GHz range is used for motion detectors in alarm systems, but due to RF interference, abandoned whit mobile phone introduction. Anyway, don't spend too much time on this one.

[Altra]

It's not a BFO or frequency shift detector. The colpits osc is set so that any non ferrous metal close to the inductor causes a change (loading) in amplitude. The buffer amp(2N2222) and 1N34 diodes form an AM demodulator or Rectifier for the sine wave. The change in DC voltage is used to set off the buzzer. The only difference between this and the average stud finder. Is that some of the DC voltage is fed back to the osc to maintain the bias voltage on the base of osc transistor. "Automatic Ground Balance"

Google "Loaded Loop Detector" they were widely used to sense cars at traffic lights.

I have the original unit and will measure the pots tommorow and post.

[Vortxrex]

Does anyone have any more Info on the Falcon?



Thank You!

Several years ago I went to a GPAA Gold Show in Salem Oregon. I brought along a small (corn kernel) sized gold nugget & a chunk of Ultramafic rock (which is typical of the bedrock here where you find nuggets) I tested the Falcon & you had to be practically touching the nugget to get a response

What I wanted was something I could use in my highbanking operations to scan along the bedrock & working face. I did not think it would work well.


It should be easy enough to figure out the values of the potentiometers, just by trying "obvious" values & tracing the signal, but don't expect it to work any better than an old Studfinder

[homefire]

OK! it nothing more then a Modified Colpit Osc but how is it doing the detection?

Were in the circuit is it pulling off the freq offset?

[homefire]

Does anyone have any more Info on the Falcon?

Looking for some values here.

Thank You!

[maikl]

Disadvantages Falcon MD20: "For very small gold the effective scanning area is about an inch wide by and inch deep.Please note that the Falcon is not a "gold only" detector. It detects any conductive items and so has uses for anyone looking for tiny metal items. But there is no ability to differentiate between different metals." http://www.akmining.com/mine/falcon.htm

[TH Jim]

Anyone have details on the probe, size of ferrite, number of coils, number of turns etc?

[Qiaozhi]

Use Google to search for "falcon MD-20". There are a lot of good reviews. Owners seem to love it.

[Qiaozhi]

You cannot watch a film on their website -> http://www.falconmetaldetectors.com/
but you can buy the T shirt ... and a cap!
Looks like they have a lot of distributors around the world for what is essentially a very simple design.

[Altra]

Here's a schematic I drew many years ago. Its missing some values. It looks like they up
graded the audio in photo. The one I had only had a piezo speaker and no ICs. It's a loaded loop detector (studfinder) which uses a ferrite core. Easy to breadboard and get working.

Mark

[amtech2005]

Thanks for the information Everyone !!
I wonder if it is sensitive to the more conductive materials ? This might be a good experimental project !!

Here is the MD-20 PDF manual :
I saw on the web this device requires motion .


HH.........Eugene