Metaldetector

From what I can tell, the whole thing is yet another internet scam.
With the few components on it, I cannot se how it can do anything practical at all....

Any serious and genuine project should provide a circuit diagram and a reasonable explanation of how it functions, if that is not clear from the circuit.

Edit - early in the video you can see it's a square pad board. Without links from the component leads to the IC pins, there are no connections!

And the poster appears to never have soldered anything electronic before, the joints likely mostly open or cracked.

This is a much more practical design; somewhat more complex, but it should really work!

The coil goes between Output and Vcc (+)

More coil may be better, but this example is not very sensitive and the iron metal blade must be near the center of the loop.

So its not very sensitive. this schematic is as poor as the video.

Thank you

...and I would like to install a potentiometer to adjust the sensitivity...
where is this interposed? does it need a resistor?

I think between tigger Pin2 and vcc?
Because in the Video is Write pin2…

As Green marked…

There are many poor or fake electronic projects on You Tooob from students in that country.

Pin 2 is not the output, It's pin 3

...and I would like to install a potentiometer to adjust the sensitivity...
where is this interposed? does it need a resistor?

That circuit is NOT a metal detector and will not work as one.

With the coil connected to pin 2 at one end and not connected at the other end, it may randomly trigger by capacitance near conductive objects or power cables - but if it works at all, it would be detecting "hum" like an open input on an audio amplifier.

The LED and/or the 555 will burn out immediately if the battery is strong since there is no current limiting.

It doesn't oscillate without any resistor coupling from Trigger to threshold and nothing makes the LED brighter.

do pins 1 and 3 behave like a single resistor? what is pin 2 for?
How is this wired?

That is a "potentiometer", the same principle as a volume control etc.

See the circuit diagram part of the photo you posted - that's its electrical symbol and pretty much a diagram of how it works!

Strictly speaking, that is a Pre-settable potentiometer, a "Preset pot" - you need a tool to adjust it, rather than it having a spindle like a volume control, so it can be turned by hand.
There is no difference in the electrical principle.

It has a fixed resistance between the two side by side terminals, and the third terminal is a wiper, a "tap" that can be moved along the resistor.

If the wiper is in the middle, it has half the resistance either side. All the way to one end, next to zero resistance to that end and the full resistance to the other.

As eg. a volume control, the signal goes to one end and the other end is ground (common, 0V).
Depending on the position you turn it, you can get any proportion of the full signal, from nothing to maximum.

To use it as a "variable resistor", connect the wiper to one end. That connection and the other end then can be adjusted from near zero up to the full value.


This is a rather larger pre-settable potentiometer; you can see the wiper that can be slid along the resistor, making contact at any point. The same principle, just without an adjusting knob:
(And using a wire-wound, rather than composite, resistor - most small ones have a black or ceramic-looking material for the resistor).




This shows a potentiometer being used as a volume control at the input to an amplifier; you can see it's the same symbol as in your photo:

Thank You !!

I would personally go for a PI (Pulse injection) type detector as they are much more reliable. Member Chemelec here had a design on his webpage but unfortunately dies a few years ago.

His site is still available, link. Look about half way down that page. Both BFO and PI covered.

Mike.

Pommie said:

His site is still available, link. Look about half way down that page. Both BFO and PI covered.

Click to expand...

No schematics or anything on that site, you had to buy PCBs or kits.

The link I posted or something at that level is more likely in the capabilities of the OP.

However, just about any design (or poking the ground with a stick) would be better than the youtube circuit he's trying to work from..

Yes, no schematic for the PI detector but the BFO has, link.
However, I think you're right, there are other schematics more suited to the OP's skill level.

rjenkinsgb said:

However, just about any design (or poking the ground with a stick) would be better than the youtube circuit he's trying to work from..

Click to expand...

Very true.


Mike.