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  • You would be surprised at what you can do with a few parts when making a detector, I just noticed I stated 0.001 should be 0.01 gram.

    Comment


    • Originally posted by Woody.au View Post
      You would be surprised at what you can do with a few parts when making a detector, I just noticed I stated 0.001 should be 0.01 gram.

      Now... that's more like it!

      Comment


      • Originally posted by ivconic View Post
        Buy shotgun and use it on monkey! No other way to deal with those!
        Drop alligator back to water where it belongs.
        Leave rattlesnake alone, let it be. As long as it keeps your courtyard - you will not have problem with damn rats and mice.
        ....
        Back to detectors.
        Was wondering about pulse rate at PI nugget hunters...
        Is it necessary good nugget hunter to have higher pulse rate or not?
        Can we analyze this at existing models?
        What would be the main pulse rate at ...let's say 5 top models we know?
        Is pps directly related to sensitivity to smallest nuggets?
        Common logic will say it is. But is it for real?
        Carl's Hammer Head can run up to 2300 pps.
        Does this makes it nice for nugget hunting?
        I made one in the past. It worked nice.
        Yet, at the time i haven't checked it on such targets as are nuggets, needle and titanium screws.
        In meantime i exchanged it for something and now i don't have it anymore.


        The relationship of PPR to sensitivity.

        I am going to bring the post above over here, because this is exactly what we are talking about.



        We see a difference between the copper, nickel and lead, due to the difference in conductivity.

        But the thickness very obviously makes the bulk of the response.

        What about the frequency? How do you convert frequency into step response? Because it is the di/dt of the switch OFF that generates the eddy currents.

        The AD8055 is specified to drive a 100 Ohm load at Gain+1.
        We don't need the high speed though, maybe we can find a better buffer with high drive capability.

        We are driving a high capacitance load. I have not yet looked for the best buffer to do that.

        Like usually, I start with what I have in the parts box and when things work more or less, I start optimizing. Lots of Datasheets to read and many Datasheets of many, many pages.

        Below, follow some explanations, Maybe you or somebody could correct them?

        The second column shows the results with 50% more power and 4000PRR
        Sample times are not changed.
        With the sample times equal, the duty cycle is where the gain comes from.
        At 10,000 cycles and 7us sample time, we have a duty cycle of about 7%
        At 6,500 cycles and 7us sample time we have a duty cycle of about 4.5%
        At 4,000 cycles and 7us sample time we have a duty cycle of about 2.7%
        So we could say, considering the difference in duty cycle when we look at the power, we get a power correction factor of:
        Power: this is an approximate number, the meter is not calibrated.
        10,000 cycles at 200mA = 1
        6 500 cycles at 400mA =*1.55, duty cycle correction factor.
        4,000 cycles at 600mA = *2.6, duty cycle correction factor.
        So we can see that the power does make a difference, but the duty cycle makes a bigger difference.
        Now, let’s look at another power factor difference.
        The field density. With an equal coil diameter, the field density is higher so it should excite the same eddy currents in a target of 3 times smaller surface area.
        This does not show with this test, because of the same surface area presented to the coil for all targets.
        Still another factor to look at, is the di/dt. Is it the same for all 3 tests?

        Ideas? suggestions?

        Tinkerer


        If we are looking for a target with a TC of 5us, we should use a sample time of 5us. If we use a sample time of 20us, we average the signal over that time and we also capture all the noise over that time span.

        When we cycle 1,000 times per second, or 1k PPR, the cycle time is 1000us. A sample of 20us would be 2% of the cycle, like 2% duty cycle with PWM.
        Looking at the signal amplitude, it would be 2% of the total amplitude.
        Now, if the original target signal was 100mV, and of a duration of 5us, taking a 20us sample would reduce the amplitude to 25mV. Integrating over 1000us will reduce the amplitude to 0.5mV.
        If we have 1mV of noise, this means that the signal is lost in the noise.

        Now, if we change the cycling time to 100us or 10k PPR, and take the 5us sample, this would be 5% duty cycle.
        With the same signal of 100mV, we are still left with 5mV.

        Now we get to the stacking of the samples.

        If we have a slow response, with a coil of 300mm diameter and a sweep speed of 100cm/sec., the center of the coil is moving 1mm/ms. If the response time is 400ms, we hear the response of the target at the center of the coil, only 100mm after the edge of the coil has already passed over the target.This makes it difficult to pinpoint the target because we hear the target not when it is under the coil, but only some time after the coil has passed over it.

        This is why we want a fast response.

        With a fast response we will hear the target about 30mm after the center of the coil has passed over it.
        This means we have only 30ms to process the original target signal and convert it into an audio signal.

        If we integrate or stack 30 samples with a PPR of 1000, we have already spent more than the allotted time.
        At best, 30 times 0.5mV will come to 4.5mV

        If we have 10k PPR, we can stack 10 times more samples. We had 5mV and end up with 50mV. Now there we have a real good, strong signal.

        After all that said, look at the duty cycle correction factor mentioned above. Factor in the duty cycle factor with the power factor and you see how the power correlates.

        You notice some losses, but you also notice, that if we increase the power while maintaining the PPR, there is a strong signal amplitude increase.

        But, if the increase of power comes at the cost of reducing the PPR, it is just a waste of power.

        Tinkerer

        Comment


        • Originally posted by Woody.au View Post
          You would be surprised at what you can do with a few parts when making a detector, I just noticed I stated 0.001 should be 0.01 gram.
          Hi Woody,

          it is not a problem to produce the electronics for a third world gold detector.
          The cost is the rugged, waterproof and durable hardware.

          And then comes the cost of sales and distribution. This will cost at least 70% of the end consumer price.

          Tinkerer

          Comment


          • Originally posted by Tinkerer View Post
            The relationship of PPR to sensitivity.

            I am going to bring the post above over here, because this is exactly what we are talking about.



            We see a difference between the copper, nickel and lead, due to the difference in conductivity.

            But the thickness very obviously makes the bulk of the response.

            What about the frequency? How do you convert frequency into step response? Because it is the di/dt of the switch OFF that generates the eddy currents.

            The AD8055 is specified to drive a 100 Ohm load at Gain+1.
            We don't need the high speed though, maybe we can find a better buffer with high drive capability.

            We are driving a high capacitance load. I have not yet looked for the best buffer to do that.

            Like usually, I start with what I have in the parts box and when things work more or less, I start optimizing. Lots of Datasheets to read and many Datasheets of many, many pages.

            Below, follow some explanations, Maybe you or somebody could correct them?

            The second column shows the results with 50% more power and 4000PRR
            Sample times are not changed.
            With the sample times equal, the duty cycle is where the gain comes from.
            At 10,000 cycles and 7us sample time, we have a duty cycle of about 7%
            At 6,500 cycles and 7us sample time we have a duty cycle of about 4.5%
            At 4,000 cycles and 7us sample time we have a duty cycle of about 2.7%
            So we could say, considering the difference in duty cycle when we look at the power, we get a power correction factor of:
            Power: this is an approximate number, the meter is not calibrated.
            10,000 cycles at 200mA = 1
            6 500 cycles at 400mA =*1.55, duty cycle correction factor.
            4,000 cycles at 600mA = *2.6, duty cycle correction factor.
            So we can see that the power does make a difference, but the duty cycle makes a bigger difference.
            Now, let’s look at another power factor difference.
            The field density. With an equal coil diameter, the field density is higher so it should excite the same eddy currents in a target of 3 times smaller surface area.
            This does not show with this test, because of the same surface area presented to the coil for all targets.
            Still another factor to look at, is the di/dt. Is it the same for all 3 tests?

            Ideas? suggestions?

            Tinkerer


            If we are looking for a target with a TC of 5us, we should use a sample time of 5us. If we use a sample time of 20us, we average the signal over that time and we also capture all the noise over that time span.

            When we cycle 1,000 times per second, or 1k PPR, the cycle time is 1000us. A sample of 20us would be 2% of the cycle, like 2% duty cycle with PWM.
            Looking at the signal amplitude, it would be 2% of the total amplitude.
            Now, if the original target signal was 100mV, and of a duration of 5us, taking a 20us sample would reduce the amplitude to 25mV. Integrating over 1000us will reduce the amplitude to 0.5mV.
            If we have 1mV of noise, this means that the signal is lost in the noise.

            Now, if we change the cycling time to 100us or 10k PPR, and take the 5us sample, this would be 5% duty cycle.
            With the same signal of 100mV, we are still left with 5mV.

            Now we get to the stacking of the samples.

            If we have a slow response, with a coil of 300mm diameter and a sweep speed of 100cm/sec., the center of the coil is moving 1mm/ms. If the response time is 400ms, we hear the response of the target at the center of the coil, only 100mm after the edge of the coil has already passed over the target.This makes it difficult to pinpoint the target because we hear the target not when it is under the coil, but only some time after the coil has passed over it.

            This is why we want a fast response.

            With a fast response we will hear the target about 30mm after the center of the coil has passed over it.
            This means we have only 30ms to process the original target signal and convert it into an audio signal.

            If we integrate or stack 30 samples with a PPR of 1000, we have already spent more than the allotted time.
            At best, 30 times 0.5mV will come to 4.5mV

            If we have 10k PPR, we can stack 10 times more samples. We had 5mV and end up with 50mV. Now there we have a real good, strong signal.

            After all that said, look at the duty cycle correction factor mentioned above. Factor in the duty cycle factor with the power factor and you see how the power correlates.

            You notice some losses, but you also notice, that if we increase the power while maintaining the PPR, there is a strong signal amplitude increase.

            But, if the increase of power comes at the cost of reducing the PPR, it is just a waste of power.

            Tinkerer
            I see. Although i haven't been for long time dedicated to PI problematic i think i understand well your elaboration.
            PPS and Power both we need to achieve small item detection. Yet to much power will cause stray signals to overcome and "sink" signal from tiny and small item we want to detect, right?
            Rising PPS itself will not solve this issue. Rising power itself ... too.
            But making good relation between PPS and Power may lead us to better success.
            Is that what are you trying to say?

            Comment


            • Tinkerer
              Glad to see you posting on the thread again. For a day or two,
              I thought that the monkeys might have got you.

              What do you consider ,as a good starting price for a basic prospecting
              detector,that meets the requirements for subsistence mining?

              Also the bench detector that you used to detect the needle with, sounds
              like a good detector.

              Comment


              • Originally posted by sawmill View Post
                Tinkerer
                Glad to see you posting on the thread again. For a day or two,
                I thought that the monkeys might have got you.

                What do you consider ,as a good starting price for a basic prospecting
                detector,that meets the requirements for subsistence mining?

                Also the bench detector that you used to detect the needle with, sounds
                like a good detector.
                Hi Sawmill,

                for the beginning, the subsistence mining detector, Why don't we call it SubMine, will have to compete with every other detector on the market. Therefore it needs to be price competitive.

                As soon as we start a marketing effort, all existing hobby detector manufacturers will jump on the wagon and peddle their stuff.

                Some prospectors will pick the SubMine, others will pick the "Bells&Whistles", because they are influenced by marketing hype or just take a fancy.

                The SubMine will have to prove itself in the field.

                The "Bells&Whistles will not last long in the harsh environment. At the end of the season, word will go around which detector is still alive and produced more gold, for the simple reason that it kept running and running, while the other one died.

                So the actual price is relative. Carl mentioned US$1000, I think it would be OK for starters. The high value of the gold makes the detectors affordable.

                But, there is one caveat. A few miners need to be thought how to find the gold with the detector. These few miners can then teach others in the art. Without teaching it will never take off.

                It is not much different as the panning for gold in the good old times. If you have never seen how it is done and nobody explains it to you, how are you going to know?

                The subsistence miners live in an environment and conditions that none of us could survive in. I have been there and done that when I was young. Today I would not last 1 week.
                But they are used to it, have grown up in this environment and master every skill needed to survive.
                If we want them to buy detectors, we need to teach them the skills needed to find the gold in their own backyard.

                About my bench test circuit. Yes, it is sensitive and yes it goes deep, but it is only a bench test designed to try out ideas, among others, for a non-motion detector.
                Talking about ideas: Motion detectors are great in places where you have enough space for sweeping. I feel that maybe it would be better to have a non-motion detector for the jungle.
                What is your opinion about that?

                Tinkerer

                Comment


                • Originally posted by ivconic View Post
                  I see. Although i haven't been for long time dedicated to PI problematic i think i understand well your elaboration.
                  PPS and Power both we need to achieve small item detection. Yet to much power will cause stray signals to overcome and "sink" signal from tiny and small item we want to detect, right?
                  Rising PPS itself will not solve this issue. Rising power itself ... too.
                  But making good relation between PPS and Power may lead us to better success.
                  Is that what are you trying to say?
                  It might be interesting to compare the power, or rather the TX field strength of a PI and the TGSL.
                  Compare the coil diameter, amps, turns and frequency of the TGSL, to the amps, turns, PPR and di/dt of a PI.
                  How do these parameters compare with detection depth for a specific target, like a 1 Euro?

                  Tinkerer

                  Comment


                  • Hi Tinkerer

                    I hate to rock the boat,but you are tilting at windmills with that
                    price . At that price you are within a few dollars of darn good existing
                    detectors,and higher than several other proven machines.

                    The TDI SL, and Infinium are just a few dollars more,and either one
                    is an excellent prospecting machine. There is a ton of good VLF detectors,
                    that will serve the purpose for less than $1000,00 . I have a bad habit of
                    keeping things real.

                    Now if your detector would run as well as a TDI SL and handle the hot
                    ground and EMI as well,but increase the depth quite a bit, for $1000,00,
                    then you may stand a chance. The same goes for the Infinium, only the
                    Infinium is already water proof,monkey proof,and You can buy one for
                    $1046.00 now. Also I haven't seen anyone step up with the so called
                    up grade that you allude to . For all practical purpose there is no existing
                    up grade from a TDI or Infinium for commercial prospecting use.

                    Some people would like for us to believe that there is,but it is BS at this
                    point.

                    Comment


                    • Originally posted by sawmill View Post
                      Hi Tinkerer

                      I hate to rock the boat,but you are tilting at windmills with that
                      price . At that price you are within a few dollars of darn good existing
                      detectors,and higher than several other proven machines.

                      The TDI SL, and Infinium are just a few dollars more,and either one
                      is an excellent prospecting machine. There is a ton of good VLF detectors,
                      that will serve the purpose for less than $1000,00 . I have a bad habit of
                      keeping things real.

                      Now if your detector would run as well as a TDI SL and handle the hot
                      ground and EMI as well,but increase the depth quite a bit, for $1000,00,
                      then you may stand a chance. The same goes for the Infinium, only the
                      Infinium is already water proof,monkey proof,and You can buy one for
                      $1046.00 now. Also I haven't seen anyone step up with the so called
                      up grade that you allude to . For all practical purpose there is no existing
                      up grade from a TDI or Infinium for commercial prospecting use.

                      Some people would like for us to believe that there is,but it is BS at this
                      point.
                      OK, my bad, I should have been more specific.

                      So, let me try again:

                      We are looking into the possibility of designing, producing and marketing a gold detector for third world subsistence gold miners.

                      Is it technically possible possible?

                      Is it economically feasible?

                      What are the parameters that would make it feasible?

                      Most of the numbers I mention are just an educated guess. I mention them in the hope that somebody can correct me and supply more accurate and substantiated numbers.

                      When I spoke of a sales price of US$1000, I meant the cost to the consumer, the subsistence gold miner in the third world.
                      My estimate, based on third world experience and precedents, is the that the cost of distribution and sales is about 70%.

                      This means that the production cost must be below US$300.

                      Is it possible to produce this machine?

                      What volume would the production run have to be to make it possible? 10,000 units? 50,000 units?

                      If you can buy the Infinium at US$1000 in the USA, it still will cost US$3,000 or more by the time it finally gets into the hands of the subsistence gold miner in Guyana. But even that is OK, if it is supported by a marketing campaign that includes onsite teaching in the real gold field and adequate after sales service.

                      Tinkerer

                      Comment


                      • Here is an idea Tinkerer, Some of the new pinpointers that are P.I based could be used as a basis for a very cheap yet powerful detector. The hardest part would be the making of a suitable coil and matching the electrical properties of the existing small coil. Then again maybe a dedicated design based on a cheap pic chip. The GB can be made by using a sample and hold type technique. What about super high frequency VLF for checking Quartz for filament Gold, a sensitive probe for detecting crevices in bedrock. The trick is to keep it simple and dirt cheap, I would not go too hard making a performance device, just something that works so people can find some Gold then upgrade to a better unit.

                        Comment


                        • As a part time coin/gold jewelry detectorist and part time gold miner, nugget hunter, I would like to see a true multi purpose detector that will work for us well in both modes, nothing now exists that will. It would have to be built around a detector like the gold bug 2, which can be used to chase tiny veins and tiny nuggets, No other detector out there comes close to this one in this category, we have tried em all, including the gold bug pro, mxt, etc. I have friends with a very successful hardrock pocket mining operation, and nothing beats the gold bug 2 for their use for tracking tiny stringers of gold while hunting for large pockets, I was thinking if a detector could be built to incorporate both the sensitivity of the gold bug 2 in a high 71khz op freq or higher, combined with a 13-14.7 freq for gold jewelry/coin hunting with switchable freqs for this, it would be great. I would be very happy with these two approx freqs in one detector, especially in a lightweight version like the f75 with disc in all metal also. We have found that the mxt is hot on gold jewelry as well as the tesoro compadre and vaquero. All the current multi function detectors on the market now fall far short when hunting micro nuggets and tiny veins. Some are very good detectors like the mxt, Vaquero, F75ltd, Eureka Gold etc. but they fall far short in some mining applications. Just some rambling thoughts on the subject.

                          Comment


                          • Tinkerer

                            Why would the price for a Infinium increase to $3000.00?
                            The price I gave is retail. If a person became a dealer and
                            ordered 50 to 100 at a time the wholesale price would be
                            pretty reasonable. If there was a real demand for those detectors,
                            there would already be dealers,and the price would be competitive.

                            If the cost is due to government fees,or laws,then ,you couldn't
                            build a machine cheap enough,that would benefit those miners.
                            There has to be a real reason ,that none of the current manufacturers
                            are interested. I do know that it is not legal to mine or even have a
                            detector in some countries.

                            If you are dealing with a product that requires smuggling,bribes,and
                            a black market,the price will always be too high.

                            Comment


                            • Sawmill,

                              you are one of the lucky 7% of the people ho live in the first world. The other 97% of the world's population, live in the third world.
                              It also so happens, that these 97% of the people produce most of the gold and raw materials that the world needs.

                              In the third world, everything is expensive. Why do you think that the electronic component distributor Digi-Key charges me a MINIMUM shipping fee of US$100? And then I still need to spend a whole day to go and pick the goods up at the FEDEX office? That is, if the value of the order is less than US$100. If the value is higher, I will have to pay 35% duty and taxes and spend 5 days between customs, banks and tax office until I get my parcel, only to find that when customs opened it, they either stole some parts or just lost them. (these surface mount parts are so tiny)

                              This is the way the third world is.

                              Not talking about smuggling or illegal use of metal detectors, we do not want to get involved in that.

                              Talking of the third world countries where it is legal to dig for gold and use detectors but just the third world reality and specifically a gold miners camp reality. The remoteness of these places makes everything outrageously expensive.

                              In this third world there are about 2,000,000 subsistence gold miners who work with pick and shovel. They must find 1 or 2 grams of gold per day to survive.
                              They accept the incredible hardship of the diggers life, because there are no other jobs for them. It is just a matter of survival.

                              The have only their eyes to find a gold outcrop. A metal detector would help them a lot, but they know about as much about a metal detector than you know about the third world.

                              Tinkerer

                              Comment


                              • Originally posted by Tinkerer View Post
                                Sawmill,

                                you are one of the lucky 7% of the people ho live in the first world. The other 97% of the world's population, live in the third world.
                                It also so happens, that these 97% of the people produce most of the gold and raw materials that the world needs.

                                In the third world, everything is expensive. Why do you think that the electronic component distributor Digi-Key charges me a MINIMUM shipping fee of US$100? And then I still need to spend a whole day to go and pick the goods up at the FEDEX office? That is, if the value of the order is less than US$100. If the value is higher, I will have to pay 35% duty and taxes and spend 5 days between customs, banks and tax office until I get my parcel, only to find that when customs opened it, they either stole some parts or just lost them. (these surface mount parts are so tiny)

                                This is the way the third world is.

                                Not talking about smuggling or illegal use of metal detectors, we do not want to get involved in that.

                                Talking of the third world countries where it is legal to dig for gold and use detectors but just the third world reality and specifically a gold miners camp reality. The remoteness of these places makes everything outrageously expensive.

                                In this third world there are about 2,000,000 subsistence gold miners who work with pick and shovel. They must find 1 or 2 grams of gold per day to survive.
                                They accept the incredible hardship of the diggers life, because there are no other jobs for them. It is just a matter of survival.

                                The have only their eyes to find a gold outcrop. A metal detector would help them a lot, but they know about as much about a metal detector than you know about the third world.

                                Tinkerer
                                ....china Australia Russia and south Africa make up close to 50 percent of world gold production not counting their non domestic mining operations ... So it is not true that 97 percent of gold comes from third world diggers.
                                Anyway ... Who wants hordes of miners running amok all over the place digging everything up and causing huge ecological damage to their countries which BTW is the true wealth of a country ... You can only dig the gold up once.
                                ...and how are these guys going to charge the batteries on these detectors BTW.

                                Moodz

                                Comment

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