“S”- tone discriminate metal detector.

[aft_72005]

False connection , Why connected 47 k resistors between two inputs of opamp !!!!!!!!!!!!!!!!

[aft_72005]

No need to connect 47K R between opamp input and ground

[Naeem]

the purpose of the couplage capacitors is for pervent any dc voltage(offset voltage)that some opamp have this.these resistors are for pervent any signal shift cause by caps and also pervent floating voltage.

[Qiaozhi]

False connection , Why connected 47 k resistors between two inputs of opamp !!!!!!!!!!!!!!!!

The LM393 is a dual comparator.
The 47K resistor is actually connected to the 0V rail. It just looks a bit odd in the schematic because it's connected to the inverting terminal, which is also connected to ground. The purpose of the resistor is to reference the input voltage to 0V.

[technos]

The LM393 is a dual comparator.
The 47K resistor is actually connected to the 0V rail. It just looks a bit odd in the schematic because it's connected to the inverting terminal

This gets to the whole issue of schematic readability. Some are so atrocious I've had to pull out paper/pencil to understand what was happening. It's like bad handwriting. This one isn't even that bad compared to others. I think a different symbol for ref. ground would help here.

[aft_72005]

The LM393 is a dual comparator.
The 47K resistor is actually connected to the 0V rail. It just looks a bit odd in the schematic because it's connected to the inverting terminal, which is also connected to ground. The purpose of the resistor is to reference the input voltage to 0V.

Yes, not regular showing resistor connect between 2 in puts of opamp.
But my opinion was other thing , as my experiment , no need add 47 k resistors .
may by some manipulation on original circuit , finally gave this result "
Add two 47 k resistor " .
I remember at on of metal detector website , saw dissection about sascho
Best vlf detector , there are circuit with very manipulation and said original
Circuit didn’t work correct . also I built sascho original circuit .it worked
Without problem . but circuit with some tips behind it

[mosha]

coil

Hi all,

what is the coil in the market can fit this detector? I want to buy one online!

kind regards,

[Pompey]

100w 0.31mm - Tx and 100w 0.31mm -Rx They must be in full resonance.

[mosha]

market brand

100w 0.31mm - Tx and 100w 0.31mm -Rx They must be in full resonance.

thank you for reply, actually I am looking readymade market brand that work with this detector to buy it.

kind regards,

[mario]

Hi

I would like to know which program opens .lay files. I would like to make this project, but I'm not sure how to get a hold of the parts lists. I'm assuming the parts list is in the lay file, but can't seem to open it at this time. Is there a free application that opens the .lay files?

[yo-g]

Sprint-Layout 4.0 or 5.0

[mario]

Thank you.

I'll make and post a component parts list that way amateurs like myself have something to play with on our spare time. It's so much easier when you have a list of items to shop as opposed to using the diagram as your reference.

[mario]

Capasitor size

Hi guys,

What is the value of this capacitor? What part number can I use. I had no idea capacitors were adjustable?

It's on Naeem's schematic's file. If the picture doesn't load you can get it here.



I know the capacitor value is found here some here:

[Qiaozhi]

Hi guys,

What is the value of this capacitor? What part number can I use. I had no idea capacitors were adjustable?

It's on Naeem's schematic's file. If the picture doesn't load you can get it here.



I know the capacitor value is found here some here:

If you look carefully at the PCB layout you will see that the unknown capacitor is in parallel with C1. This allows you to insert more capacitance for coil compensation if it's needed. Presumably C1 is there to help achieve the correct initial phase-shift between TX and RX.

[sevar12]

no this is C4