PLL metal detector MC14046

[reptooyep]

Hi everyone,
I want to build a simple metal detector for my 4 years old kid. I made once a BFO detector that works not so bad but you have to adjust the
coil manualy during the use.
I found on the scheme section a PLL detector with NE556 but the only PLL i have in my electronic stock is a MC14046. I found the scheme on the net :

Does someone has already build it ?
I have few question on this scheme :
1st : The frequency tuning cap should be connected to pin 6 and 7 and not to ground on 7 (green point on the scheme) ? On the datasheet, there is no ground to the cap.
2nd : The VSS pin should be connected to ground directly and it's cabled to ground by a 1.5µf cap, i don't understand this fuctionning.

This scheme is hard to read cause the crossing are not clear, there is no point to show the connection between several wires.

I also join my lay file ..iwan PLL.zip

Thanks

[Skippy]

4046 chips are notoriously unpredictable. Every one is different, they drift with temperature, they are very sensitive to supply voltage changes. Only use them in certain places. This poor-quality circuit will likely lead to disappointment.

[Teleno]

4046 chips are notoriously unpredictable. Every one is different, they drift with temperature, they are very sensitive to supply voltage changes. Only use them in certain places. This poor-quality circuit will likely lead to disappointment.

The VCO is sensitive to supply voltage, as specified in the datasheets. The HEF4046B version is more stable though: http://www.nxp.com/documents/data_sheet/HEF4046B.pdf

[Skippy]

Unfortunately the Original Poster doesn't have that part in his stock.

I presume the reason the 2.5V reference is used is because of the supply voltage sensitivity.

[reptooyep]

Ok, it sounded nice to use a PLL for this but you are right when saying pll are unpredictible ..
By the way, what do you think of the shematic and the question i answered ?
If it's not the good schematic for a simple detector, what would you advice me for a simple detector for kid ?

[Skippy]

The Bounty Hunter Junior is pretty good for the money, it also seems to be sold with other brand names, like Discovery and maybe even Radio Shack.
https://www.walmart.com/ip/Bounty-Hu...tector/8154774

[reptooyep]

Thanks skippy but i'm looking for a diy unit (layout file or schematic).