Carl Moreland VLF Detector schematic

Does anyone know what the frequency of this detector is? I got it off the internet, but there wasn't any other info on it. Nothing on the Geotech1 forum. It was either copied from a Carl Moreland board, or Carl Moreland copied it himself. There are notes to that effect on the top left and bottom right corners. No inductance, shape, type, etc. listed for the coil. Some IC's do not have the pins marked and I saw a diode with no markings. It lists 2 channels as being non-ferrous but no ferrous channel. Any help on the frequency would be appreciated. The rest of the stuff I can figure out. The schematic is too large so I will upload it to the download area. I will call  it the Carl Moreland VLF Circuit. Thanks again, Dusty Carl

Ok it's in the download section as a zip file. The next post above this one is a link to that download or use this one.

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Posted on: January 11, 2015, 08:15:07 pm

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Just looked at the VLF schematics in the download section, and the schematic looks similar to a LOBO or something Tesoro might have made.

Dusty Carl

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A bad day at gold prospecting or metal detecting is better than a good day at work.

		Quote:			Posted by GoldDigger1950
	On the left, center of the schematic is the TX section. In order to calculate the frequency, you need to know the value of the coil. I didn't look at the entire schematic because it wasn't printed near the coil where it should have been. Sorry, I am in the midst of some important deadlines can can't afford the search for information. But if you have the time, look for the coil inductance and use the formula for designing a tank circuit for the answer. You need algebra for this. I know. First time ever, right?

Thanks for at least trying to help GD. I am good with the formula thing.  I just haven't found the the inductance info anywhere yet. It's like saying "how much is 2 + ?" and nobody knows what "?" Is. Lol. Maybe if I can find the original source again,  and try to back track from there. In the meantime I hope someone beats me to it.
Thanks again.
Dusty Carl

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A bad day at gold prospecting or metal detecting is better than a good day at work.

When I get it done or even partialy, I will update schematic.

Dusty Carl

Posted on: January 12, 2015, 11:46:14 am

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		Quote:			Posted by golddustcarl
	When I get it done or even partialy, I will update schematic. Dusty Carl

Note these are calculated values and not something that I took from an actual circuit.

Well here is what I came up with for a Colpitts oscillator and those values.
20 KHz-------tx = 1.482 mH
14.5 kHz-----tx = 2.819 mH

20 KHz-------rx = 1.919 mH
14.5 kHz-----rx = 3.650 mH

Other values in the synchronous demodulators and phase adjusters might have to be modified to accomodate those frequencies.

Dusty Carl


Posted on: January 12, 2015, 01:10:23 pm

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If you are planning to make a DD coil, keep the rx coil the same number of turns as the tx coil. (Out of convenience) and replace the .033 uf cap with a .043 uf. (You can just add a .01 across the .033 to get that value).

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A bad day at gold prospecting or metal detecting is better than a good day at work.

Found out the frequency is 10kHz. That would yield these inductances for the two coils.

Rx......7.6758 mH
Tx......5.93     mH

If you use a DD coil make both coils identical using the same amount of inductance as the TX coil, but change the value of the .033µF cap across the RX coil to .043 by adding a .01µF cap in parallel with it.

Dusty Carl

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A bad day at gold prospecting or metal detecting is better than a good day at work.

Yes , Eugene and Mr. Global [Homefire]  have a Boat-load of Schematics, somewhere ?? 

Just ask if you need something , Same day service available .  LOL


Regards.................Eugene




2015 !!!!!

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