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Offline Gwil
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« Reply #10 on: May 17, 2013, 08:32:25 am »
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Hi Xavier

Could you post the schematic of the design you're experimenting with, or a link to it?  Thanks.

Gwil



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« Reply #11 on: May 17, 2013, 07:18:02 pm »
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I meant to add, and how you have the scope connected.  Thanks

Gwil


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« Reply #12 on: May 18, 2013, 11:34:53 am »
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OK here it is. I connected the scope probe to pin 1 LF353 and to pin 6 UA741 then other side of probe to scope Ground (Did not work) virtual ground (Did not work) batt neg (Did not work)

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Xavier

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« Last Edit: May 18, 2013, 11:37:20 am by xavier » 		Logged
So many questions so little time
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« Reply #13 on: May 18, 2013, 11:44:44 am »
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Emmmmm!    Some is amiss.    The virtual Ground should work for the out put of both OP Amps.

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« Last Edit: May 18, 2013, 12:03:26 pm by homefire » 		Logged
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« Reply #14 on: May 18, 2013, 11:50:19 am »
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I know but some how I'm getting Zip, Nada and nothing LOL did not have time to fool around with it lately but probably will tomorrow .

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« Reply #15 on: May 18, 2013, 05:36:56 pm »
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Hi Xavier

I'm not clear what sort of output you hope to get.  Your schematic resembles the first couple of stages of a Tesoro type VLF MD, but with the synchronous detector section replaced by a direct connection.  The second stage has X50 gain but has a low pass roll off at 7.2Hz, which is going to seriously attenuate the sine wave, assuming it's several kHz (you didn't actually say what it is). 

Gwil 


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« Reply #16 on: May 19, 2013, 12:26:45 am »
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Xavier I have a silly question, you said you laid the RX coil over the TX coil but you didn't mention whether you nulled the arraignment?

Dennis

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« Reply #17 on: May 19, 2013, 08:08:45 am »
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 Hi Gwil

Frequency is 14.5 Khz same as the TGSL

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Xavier

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« Reply #18 on: May 19, 2013, 01:55:04 pm »
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Thought so.  To sum up, the first stage of your setup amplifies the receive coil 14.5kHz signal by a factor of 46.8.  Its output goes to the second stage, which is only designed to handle the low frequency pulses produced by a synchronous detector when the search head passes over a target.  Have you looked at the "TGSL 101" document?  It explains the functions of all the various sections of the design.  It's available here:

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Good luck,

Gwil


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« Reply #19 on: May 19, 2013, 02:39:34 pm »
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Hi Gwil

I have build the TGSL with success and I'm using it all the time but it was quite a problem getting it to work properly (Transistor related). The way that I have been doing the experiment is with the TGSL coil attached to the differential amp with a second stage almost the same as the TGSL yet when I pass metal over the coil I have no output signal, I think that you will agree that there should be one. I have replaced the op-amp primary and secondary

Regards
Xavier

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