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  • Gee, you made a completely different approach. On the IGSL topic I replied to you with explanation about the TGSL opamp bias problem, and you already fixed that by the other approach. My suggestion was to go for FET input opamps instead. This works too - either the mountain comes to Muhammad or Muhammad goes to the mountain.

    BTW, I found that replacing R43 with 680k works perfectly for me. Simulation says 750k would be even better, but I don't have any in my stash, and I cant buy any on my li'l island.

    Comment


    • Originally posted by Davor View Post
      Gee, you made a completely different approach. On the IGSL topic I replied to you with explanation about the TGSL opamp bias problem, and you already fixed that by the other approach. My suggestion was to go for FET input opamps instead. This works too - either the mountain comes to Muhammad or Muhammad goes to the mountain.

      BTW, I found that replacing R43 with 680k works perfectly for me. Simulation says 750k would be even better, but I don't have any in my stash, and I cant buy any on my li'l island.
      Sorry for the confusion. The above diagram (I will call it the Lobo Mod) was something that I had already done to my original TGSL which I was not completely happy with and was still looking for a better solution. Which is about the time you offered your thoughts.

      I tried your suggestions on another TGSL and like the results. So now I have one TGSL with your mod and another one with the Lobo mod. I was hoping there would be some benefit of incorporating the two.

      Both of these detectors are working very well, but I always am looking for things to tweak them a bit.

      Thanks for the tip on R43. I will give that a try.

      Jerry

      Comment


      • I happened upon this old thread started by Porkluvr in 2008 which sums up and sheds some light on what I was trying to do.

        http://www.geotech1.com/forums/showthread.php?t=14998

        It is interesting on how the same subject keep coming back from time to time.

        Jerry

        Comment


        • Hello. show me breakdown on the circuit schematic. PLEASE help me

          Comment


          • I couldn't find the link to the latest, so here it is.
            Don
            Attached Files

            Comment


            • Hi Jerry,, "my goal was to be able to set a steady background tone when searching for coins"

              What do you get or need when you find a coin?



              Is it personal preference that you want a tone on continuously in order to give the impression of working the machine right on the sens threshold ??

              S

              Comment


              • Originally posted by golfnut View Post
                Hi Jerry,, "my goal was to be able to set a steady background tone when searching for coins"

                What do you get or need when you find a coin?



                Is it personal preference that you want a tone on continuously in order to give the impression of working the machine right on the sens threshold ??
                S
                Hi Steve,

                It is a personal preference which I think can give maximum depth out of a machine. However, since the TGSL is a motion only detector, just adding a threshold control did not give the desired results. I worked on it for quite a while last year until I happened on this old thread which showed that someone else had already tried this with about the same results. So I decided to give it a rest for a while.

                http://www.geotech1.com/forums/showt...threshold-tone

                Jerry

                Comment


                • HI DEAR
                  > PLZ IF U CAN HELP ME ABOUT SNIFFER XR 71 THAT I HAVE A PROBLEM WHEN I ASSEMBLAGE THE DEVICE
                  > I HAVE 3 PROBLEMS
                  > 1. WHEN I CONNECT THE LOOP THE FUSE BURN OUT I TRY TO FIND ANY SHORT I DIDN'T FIND ANY THING.
                  > 2. THEIR IS SEPARATION I DON'T KNOW THAT IN THE CCT. CARD OR IN J1 & J2 IT WORK Intermittently.
                  > 3. THE RANGE WITH 1 METER LOOP IS JUST 30 CM.
                  > I APPRECIATE UR RESPONSE SO MUCH & THANK YOU.
                  >

                  Comment


                  • I am making coil for TGSL EDU.
                    Wound 107 turns on coil jig... standard dimensions from manual for TGSL Coil making
                    255x137 mm
                    0.25mm copper anameled wire
                    I have inductance of 6.53 mH and resistance of 27 ohms.
                    It is still on jig.
                    Is that OK ?
                    Can I remove it and get going with isolation and shielding ?

                    Comment


                    • If you want to get very precise just remove one turn to get below 6.5, as compacting the coil will increase inductance a bit.

                      Comment


                      • TGSL EDU (from Silverdog kit) is finally all completed and assembled with coils
                        RX 26 ohm 6,62mH
                        TX 24,9 ohm 6,02mH
                        wound up on jig as described in manual
                        (isolated, than wraped in mylar - conductive side out (left 1-1,5 cm blank for break in faraday cage)
                        (maybe too much overlap - can it hurt ?)
                        and plain wire wound for shield connection for both coils and as finish one more layer of isolation tape)

                        connected two pots and switch
                        connected with usb cable to PCB folowing manual - grounded on coil and on PCB

                        tested on bench
                        I have max 8 cm on 1 EURO coin in air if I place coils together

                        when I switch to K2 i K3 connection I have no detection
                        tried pots at various positions

                        ballancing is not very clear for me
                        my voltmeter has scale for 200mV AC but I don't trust it ... no oscilloscope yet...

                        can someone please explain functions of switch K1,2,3 and pot DISK.
                        if switch is on disk pot works and if switch is on all switch is doing ...
                        Last edited by sdesic; 05-20-2013, 06:48 AM. Reason: addin something

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                        • I have tried nulling and I have made 00,8 mV AC ... without power it says 00,6 mV AC
                          started from 300mV
                          it is good BUT I have detection range of 1-2 cm

                          While I was testing with RX coil off and voltmeter on about 2 minutes from start
                          detector went beep, beep, beep ...
                          3-4 times a second ... pots are not responding, when I changed position of coils then it stopped beeping.

                          Any help would be appreciated.
                          Is it coil or PCB ?
                          What do to next ?

                          Comment


                          • Originally posted by sdesic View Post
                            I have tried nulling and I have made 00,8 mV AC ... without power it says 00,6 mV AC
                            started from 300mV
                            it is good BUT I have detection range of 1-2 cm

                            While I was testing with RX coil off and voltmeter on about 2 minutes from start
                            detector went beep, beep, beep ...
                            3-4 times a second ... pots are not responding, when I changed position of coils then it stopped beeping.

                            Any help would be appreciated.
                            Is it coil or PCB ?
                            What do to next ?
                            That can be an indication of a dead battery. Also, make sure your speaker is far away from the coils.
                            Don't spend too much time on nulling, just find the deepest null, mechanically secure them and leave them alone. What type of cable are you using?
                            See post #5022 here: http://www.geotech1.com/forums/showt...-SABRE/page201

                            Comment


                            • TGSL EDU
                              I am using power adapter 12V 1A
                              speaker is piezzo from silverdogs kit - it is away from coil
                              the best results so far is 10-11 cm for 1 EURO coin
                              and if I switch to K2 K3 connection ... don't have any detection whatever position pots are in
                              using USB cable

                              tried with two shields connected to ground
                              and with both ends and shields connected with ground in coil and close to PCB

                              Comment


                              • I have build surf pi before and it has sounds other that detecting metal... this one has not.
                                Whole range of pot sens is clear - no sound until metal is introduced.
                                12V and 8V are OK
                                Pin 4 of ICs has -6V

                                Comment

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