New 2 Box Design

[TH Jim]

Hi Folks,

I would like to share this 2 box project with the forum. I have built and tested it on breadboard at my work bench. It can detect a 500ml drinks can at a distance of 1 meter, an Aluminium plate 135 x 195 x 1mm, at a distance of 1.5 meters, and a 0.75L glass jar containing approx 2Kg of copper coins at a distance of 1 meter.

It is a little tricky to set up - especially the audio offset pot, this makes a huge difference to performance, so be patient! I'm sure the design can be improved, I didn't have enough time to get it really sweet. Anyone who would like to improve it please feel free.

I have attached the scheamtic(drawn in Eagle), Hope someone finds this useful!

Cheers, Jim.

[kt315]

can you convert the file in OrCAD or P-CAD type one? TIA.

[Jose]

Hi TH Jim
Thank you for sharing scheme
I have some doubts, what is the value of power supply.
The coils are square or round. What is the section of the wire.
The approximate distance between TX and RX.
Sorry so many questions.
A cordial greeting.
Jose

[TH Jim]

Sorry KT315 I can't convert to those file types - don't have those applications.

Apologies Jose! yes I have omitted the power supply values!

Both circuits use 9V

The coils are 13" circular, the wire was out of my junk box so i don't know its exact size but 0.2mm is about right.

The centers of the coils are 1 meter apart.

Regards Jim

[Rumcajs]

can you convert the file in OrCAD or P-CAD type one? TIA.

Here is one translated sch. package:

Brg

Rumcajs

[Rumcajs]

Hi Folks,

....

I have attached the scheamtic (drawn in Eagle), Hope someone finds this useful!

Cheers, Jim.

Hi Jim,

i m dont understand the what is function the U4A?
The U4A output is directly grounded, the 470 microfarad capacitor is shorted.

Please send me your answer, let me know... Many thanks!


Brg

Rumcajs

[TH Jim]

Hi Rumcajs,

Thank you for looking

IC4A is a virtual ground, the positive input is held at half the supply voltage and the negative input is fed directly from the output thus making a voltage follower at Vcc/2. The cap is not shorted but is connected between the virtual ground and 0v (negative rail).

It is a simple design and therefore a basic detector, but it works!

Regards, Jim.

[ApBerg]

Hello Jim

Thanks for the schematic ! (converted to png.)

Best regards.

Ap

[Rumcajs]

Hi Jim,

many thanks!
Rumcajs

[nelson]

Good job ApBerg

Hello Jim

Thanks for the schematic ! (converted to png.)

Best regards.

Ap

[ApBerg]

Good job ApBerg

Hello Nelson,

Thanks is for TH JIM, he made the circuit !

Best regards.

[ikumi5]

hello!!
a quick simplified pcb etch with this project (no audio, meter only using single ic (LM324))





regards!!!
ikumi5

[TH Jim]

Nice ikumi5

Are you going to build it?

Regards, Jim.

[ikumi5]

yeah! adding modulator in the transmitter section is much better.

regards!!!
ikumi5

[TH Jim]

Do you mean modulating the Tx frequency at an audio frequency so that the recieve signal can just be amplified for audio output?

Regards, Jim.