Falcon MD20

[homefire]

Start reading on page one of this thread. It's all here.

[Wahyu]

thank Tim, i'm from Indonesia,
this sch please correct me

[Tim]

Hello my neighbor.Your schematic has a few differences to the one posted here. When I re-checked the board here, it is correct. I will put them here so you don't have to search.
This board LAY file is the one here called LAY1.

[dom44]

this circuit works I am still playing with the shielding and some mods it is just as sensitive as the commercial one the copper ring is very important and the coil shape I will post a video and more detail soon.

[homefire]

Tim that board shows a IC. Schematic does not. Is that LM555 and unlabeled pads speaker ?

[dom44]

ic 555

yes it does the 555 is just an oscillator to drive the speaker it replaces the sounder i am currently working on a vco as i think it will improve the sensitivity by altering amplitude as well as frequency of the sound at the moment its basically on or off switched by the final transistor, but as it stands it works just like the commercial unit will pick up a 3mm piece of component wire at 5mm easy the copper ring is the key and its placement in relation to the ferrite rod and the the coil shape, it doubles or triples the sensitivity of the unit.

i have also found the shielding to be important it must be a broken circle if it forms a ring will desensitize the unit as i have found through experimenting the same as a conventional metal detector coil. i am playing with conductive graphite on the end cap to act as a shield.

[dom44]

my coil head

[homefire]

Cool. What wire did you use and how many turns about. I have all parts. Need to figure a way to burn a board from that lay file I guess.

[dom44]

I found with my ferrite rod it was 60 turns to get 300khz i think the gauge was .22 mm i am working on a layout in sprint right now just trying to get the VCO to work right.

[homefire]

Good Stuff. Thank You.

[dom44]

Resistor missing

I left out a 3k9 resistor emitter of T2 this is fixed now and i have just built the second one on the PC board and I know it works well. with just the LED and no sound when adjusted you can see the LED flicker at over 100mm with the tip of a small screwdriver near the search coil.

[Tim]

Sorry y'all for not replying- been a bit crook. Great progress dom !! I ended up buying an original off fleabay- too many un-finished projects. They are a great little piece of kit. Glad you could explain to homefire about the 555.
I hope to return and contribute here more in the future, but I have just started my second month of Chemotherapy for inoperable stage IV pancreatic cancer, so have been a bit doughy. It's been knocking the crap out out me, but I hope for better health and less side effects in the future.
All the best to you all at this wonderful site. : )

[dom44]

sorry to hear about your cancer Tim have lost a lot of family and friends to it to the point a did a lot of research on natural therapy's and there is so much we are not being told i know this because i have quite few proven cures that don't involve poisoning your body or radiating it or cutting it up, look up Hoxsey formula or essiac for a start,
I have almost finished the VCO section works great but not getting enough tonal change for my liking I have to play with some part values still.

[dom44]

This is the VCO looking for A,B and C Values A is 1meg and works fine image4 is wrong BC327 is upside down cant remove it.

[homefire]

Dang Tim. Sorry to be hearing that. You can do fine without a pancreas. Can't they remove it or has it moved around ? It's Never over until the Fat lady sings, Right ?

Dom, Novel Idea on the VCO. What Diode was you thinking there. I see a zener being used in other Nand Gate VCO's. Don't understand how they work.