PimentoUK

In a nutshell ... it sounds like you've understood it. As I've never used BBS/FBS machines, I never took the time to understand the details, so I can't explain FE/CO properly, but that Knowledge Base pdf seems to cover it, though I'll add another ML article to that post, just fer info.

It has been discussed on Geotech1 and Dankowski's forum. I'll try and pull together a few links that are relevant. There's also a technical paper on ML's website explaining some of FBS operation. The summary is: FBS transmits its two frequencies CONSECUTIVELY. It produces 8 cycles of 25 kHz, followed by 1 cycle of 3.125 kHz, then repeat. The key point is that during the 3.125 kHz transmission, there is no other signal present, so there is just a square-edged waveform with a 160 microsecs gap between two consecutive transitions. This is used as a crude PI signal, which allows the detector to analyse a target differently to how a continuous sine-wave machine would see things. By combining the analysis of 'crude PI' and the 'continuous waveform' (that goes back to BBS machines like the Sov) it's possible to create a 'FE' figure, in addition to the more conventional 'CO / conductivity' one. Multi-IQ does transmit all three of its signals SIMULTANEOUSLY , in a complex square-edged waveform that clearly has a lot of 39 kHz, in addition to the 7.8kHz & 18.2 kHz signals. So there is never a point where there's a big long gap between waveform transitions - about 20 microsecs is as big as it gets. So this 'crude PI' method can't be applied. So to produce FE/CO figures, the Equinox would have to generate something close to a BBS/FBS signal. Long gaps between signal transitions are needed at some point. Possible solutions would include a user choice of Multi-IQ or FBS operating modes. Or perhaps a mashed-together mode, such as one cycle of 5kHz followed by a burst of Multi-IQ waveform for 200 microsecs then repeat. The first of these is simpler, as nothing 'new' needs to be engineered, the existing know-how just needs transferring to the Eqx platform. Here's the Minelab Technical article that mentions the 'FE' - determining technique: ML article There are a couple of other simple 'how detectors work' articles on ML's site that are perhaps too basic, but might be interesting to some: www.minelab.com/usa/support/knowledge-base/articles Here's a couple of Eqx threads on Geotech1 which show the waveform: Geotech EQX Freq Geotech EQX general This FBS thread on Dankowski's Forum unfortunately does contain a lot of poor info as well as good info, and the waveform screengrabs that Yeasty posted up have now 'gone' , so it's not so good now. Dankowski FBS geekery

Quote:"Unless there is something inherently limiting regarding Multi IQ's ability to support Fe-Co target ID ..." There is. The simultaneous multi-freq technique used in the current Equinox models has no means of determining the 'FE' characteristic of a target. But ... as the Equinox would appear to be able to generate any frequency waveform ( it's created by software ) it could be made to run a BBS/FBS-style signal, and hence have CTX-like performance. The limiting characteristics of the coil may affect what is possible. The Eqx seems capable of working at 5kHz and 40 kHz , FBS works at 3.125 kHz & 25 kHz, so maybe a tweaked FBS operating at slightly higher freqs would be viable. There's nothing magical about the FBS frequencies, the 1:8 ratio isn't 'golden' , it was chosen because it was easier to create in the early Sovereign-era electronics.

@ Cobill: I think you've made an error in purchasing those '8000 mAh' cells. The highest capacity I've found available from a known/reliable/trusted brand is 5500 mAh. Those cells in your link are very likely to disappoint, and may well have a capacity some way below 2000 mAh.

I was aways puzzled as to why the Fisher 15" coil was round in shape. Everyone seemed to think the 11 x 7 bi-axial stock coil was a good shape, and presumably the machine would in some way be 'optimised' for that shape. So why wasn't the 15" coil actually a 18" x 13" or suchlike? If you're hoard-hunting, then I guess shape doesn't matter that much, so the round coil would be acceptable. But heavy ... if you're only planning on light-duty use, there is no doubt some weight-saving possible. I have tried large-target hunting with my F75 / stock coil. It works, but really needs a bigger coil in the 15 - 20 inch area to do the job properly. I never bought the Fisher 15 coil, and since buying the Eqx, I've found its stock coil is large enough to give reasonable 'hoard-hunting' potential. So hopefully in the next month I will be trying it out on some farm fields that are ready for crop harvesting.

The problem with the T2 is going to be down to the 'sensitivity hole' , the worst case being when Disc is set around 25-30. The F75 in DE (default) mode has the same issue, when Disc is set to around 11. A quite significant loss of sensitivity occurs, not that the User Manual makes any mention of it. On the F75, increasing Disc from 1 through to 11 causes a progressive loss of sensitivity. Increasing it from 11 through to 23-ish steadily increases sensitivity back to 'full' level. I guess on the T2 this is roughly 1 thru 25 thru 50 ( I've never used a T2) The F75 thankfully has JE ( Jewelry ) mode, which does things differently, and seems to not suffer the 'hole', being sparky regardless of disc settings. I haven't really tried large iron hunting on my F75, so I can't guarantee JE is the best mode, though.

Shelton is a man of few words .... He's demonstrating various 3D printed modifications to his Equinox with telescopic carbon shaft. Audio is in Polish.

Quote:" Are you using a BMS module inside the 4s1p tube? I don't know if I'm correct but seems to be the easier combination for a self balanced recharge .." Lithium-Ion cells don't self-balance, and have to be forced to charge correctly. This means either: A seperate charging connector bringing out all the cell terminals, (which will be 5 connections in the case of this '4s' pack) and charge with an appropriate balancing charger ( eg. R/C model charger ) or: A charge balancing circuit integral to the battery, allowing simple charging ( eg. current-limiting), on just the end terminals. In the case of using a seperate charging connector, the pack can be charged quicker, as all the thermal issues are moved to the charger, which can have high-power transistors/heatsinks etc as needed. A balanced charging circuit has less ability to juggle the currents through each cell, so generally they seem to be used in conjunction with slow ( trickle ) chargers. A seperate charging cable still means a battery protection circuit is needed, however, to guard against over-discharge, accidental overload/short-circuit, and possibly overheating. That is what the module pictured in OBN's post appears to show. It's also wise to fit 'gross overload' protection on a high-powered pack like this. That would include a conventional one-time wire fuse, a thermal fuse, and possibly a self-resetting 'poly-fuse'. I currently have a dismantled 5s lithium pack from a handheld Vax cordless vacuum cleaner. That has charge-balancing internals, and there's a surprising amount of stuff on the large circuit-board inside the pack, it's the full size of five 18650 cells. I also have an EBL 9 volt PP3 apart, which obviously is much lower power, and only two cells. There's not much to the balancing electronics in that. I don't know what techniques either of these packs use to achieve balancing, they are probably quite clever.

Bonding plastics is always a bit tricky, especially if the type of plastic is unknown. It should be possible to find out what the Garrett is made of, and most of the scrap bits will have some recycling labelling. But from experience, computer printers etc can use all sorts, ABS, ABS + polycarbonate blend, Polystyrene. So I would probably go for thixotropic cyanoacrylate. However, a few tiny self-tapping screws through the lot wouldn't be a bad idea, except they would rust, so a bit of paint would be needed.

I also thought a 'fin' bonded onto the flat back of the cap would work. I've definitely seen that type of device used on torches ( US: flashlights), the long 3 x D-cell sort. A single central flat rib, that can be gripped between thumb and index finger. I have plenty of scrap plastic... that T - profile is something that could be found in commercial equipment enclosures, like computer printers , I'm going to have to rummage tomorrow.

When running on a standard PP3, you are presumably adding a rubber/plastic etc insert into the extended cap ? On the subject of modifying pinpointer end-caps : I think that's one of the design flaws of the original Garrett propointer, which seems to have been repeatedly copied by everyone, the big names and Chinese clone makers. Unscrewing the thing if you've got wet, muddy or cold hands is terrible, the smooth slighly undulating pattern is hopeless. What's needed is an aggressive, finer-pitched grip. Something similar to the teeth of a gear wheel, or the square splines of toothed drive belt pulleys. I actually rummaged through my 'engineers junk box' years ago, to see if there was anything suitable I could fit on there with some lathe work. I never did do anything ... and it still frustrates me today.

It might be an idea to add a link to the original thread on this topic, so folks can remind themselves of prior discussions. Cylindrical lithium cells are available in AAA size, thought they usually refer to them as '10440' size ( 10 x 44mm), and they are very similar in length to PP3 9V batteries. Two of them would make a decent PP3 substitute, the capacity of them seems to be about 350mAh, adequate, though not excellent. But they would at least be removeable individually for charging, so there would not be any constraints caused by having them made up as a two-cell assembly. Whilst thinking about making my '2 x foil-pouch cell' PP3 substitute, this AAA idea seemed workable.

This user back in 2018 had the same issue, he ended up with a control box replacement: Dankowski forum link: Dankowski: error41

It would certainly be worth experimenting with added weights, to see how much the battery pack could weigh. Then use that data to influence the design of a homebrew battery pack. Going by its appearance, and my familiarity with the F75, I expect it could be quite a substantial battery. 12 x 18650, 8 x 26650 may be practical. Or 11/12 x A-size NiMH.

One of the reasons 18650 size is favoured is because that size has had a lot of development put into it, firstly in laptop computers, then electric vehicles. Other sizes, both larger and smaller, seem to have lower capacity than what you would expect, based on 18650 specifications. The internals of these cells are basically rolled up sheets of aluminium & plastic, so any technical improvements should immediately be applicable to smaller/larger cells. It just doesn't seem to have happened. I have just tried a 'math comparison' with 26650 size , and I would expect a capacity of over 7000 mAh should be attainable. But so far, 5500mAh is the best claim I recall seeing for one. [this is the 'ShockLi' brand, which sound awful and dodgy, but seemingly are not, and are also sold under other names, particularly when re-packaged as 'protected' types. At low-drain 0.2C rate ( ie. about 5 hours discharge time ), they test at near 5800 mAh] In practice, energy per unit volume is not always the important characteristic, energy per gram weight may be more relevant. If the cells are lighter as a result of being under-capacity, they will meet this requirement. Does a detector battery need to be small? Or is there an optimum weight range, for example?

Individual cells come in two 'flavours' , raw cells, and one with protection circuitry integrated. Protected cells are slightly longer, due to the pcb etc, so won't fit every e-cig, flashlight/torch etc, and they may limit the discharge current too much, which makes them unsuitable for high power uses, like RC flight packs, ridiculous vape rigs. RC packs/cells tend to state the max discharge rate, in terms of 'C', so a '10C' pack can be drained at 10x its capacity, eg. 22A for a 2200mAh pack ... probably similar for vape branded ones. Then there are Lithium-Iron cells, which are specifically aimed at the very high drain applications, but have noticeably lower capacity, 60% of most other Li cells. They need charging differently, too, a max cell voltage of 3.8V, not the more common 4.2V. They are not really suitable for our needs. And there are now some 'graphite' chemistry variants, that are charged to 4.35V, the RC sellers brand them Li-HV. Probably good for model power, but not beneficial for our low drain uses. As for recommendations ... Watch out for fraudulent cells, like unbranded types claiming high capacities, anything with xxxxFire in the name -- all guaranteed junk. Sanyo-Panasonic are considered the best brand, their best 18650's manage 3400 mAh.

All that speculation about the battery left me wondering what is actually inside the supplied NiMH pack, and whether keeping the same number of cells is best for a homebrew, or whether one or two more would help. That is: a 11-cell or 12-cell NiMH would be closer to the original design voltage of 16V (fresh) to 11V (flat).

You are being harsh about my 'negatives'. Yes, attaching your pointer to a lanyard/cable will stop you losing it, most pointers nowadays have a loop built into them, similar to cameras etc, so this can be attached. And for older pointers, like the orginal black Garrett, you can buy a special tabbed washer that fits under the battery cap, to give it a cord attachment. But not everyone wants to be attached to their pointer, just as they don't care for corded headphones attaching them to their machine. If you don't use a pointer, you don't have to carry a spare battery for it. Expense: this is a BIG problem for newcomers. Spending 150 US Dollars on a top brand pointer is a major investment, when compared to spending Zero on the no-pointer option. There are now a number of cheap copy/clone/lookalike pointers priced below 30 US Dollars, some of which seem to work OK , though it's no doubt a choice minefield. Beep or silent is an option on a number of current pointers. One of the first modifications I did to my Propointer was to ( rather cleverly, I think ) add a beep on/off control. I had plans for controls of the white LED, too, but I just settled on sticking black electrical insulating tape over it, if I wanted to be discrete.

That's what I was describing, I figured you would know without me hunting down an Amazon/eBay listing of one. I don't think your 12 to 110 converter will limit things, after all 12 V at 0.4 Amps is barely 5 watts output, efficiency may be a poor 50%, so 10 Watts consumed from the 110V , that's not going to trouble your converter even on a hot day. It's worth keeping an eye on eBay for a secondhand RC charger. They are likely to come up quite often. Search in the 'Toys & Games' section for 'turnigy charger' , 'IMAX charger' , 'skyrc charger' , you'll soon track one down. I've added another Turnigy charger to my earlier post, the Accucell6, it's simpler and cheaper, as it's a 12V only input power, not AC mains.

There are simple homebrew ways to prevent/reduce tip wear. When my original black Garrett Propointer wore through ( the potting resin was visible ) , I cut off the pointless 'sifter blade' so it was round at the tip, and fitted a short 40mm length of heatshrink sleeving over the tip. A little EVO-STIK or similar light duty adhesive helps hold it in place. It lasts 4 - 6 months ( dirt digging with heavy use ), and has been successfully protecting my pointer for 4 years+ now. Regarding: " I assumed [a pointer] was something everybody used to speed things up in locating an object" They certainly can save time, it depends on how you use them. But their ability to help avoid damage to finds by clumsy digging ( in dirt ) is their best feature. Knowing where the target is, and hence where to dig/not dig, accurately, is very effective, I rarely damage finds now. They have quite a number of uses, though many are dirt-specific. This is a post of mine from another forum: Advantages: a)finding targets in the sidewall of a hole b)verifying the target is in the bottom of the hole c)allows you to close in carefully on the target, avoiding damage to it d)very shallow targets can be precisely pinpointed before digging, reducing digging e)a probe will often find things in the spoil-heap more easily than the traditional methods f)on pasture, the target is often in the turf. A probe will help you extract it without ripping the turf into bits g)on park land, for example, where broken glass, sharp metal rubbish etc, occurs, a probe will minimise how much handling of the dirt you do. h)where multiple targets occur, eg. a nail and your intended target, the probe will allow you to seperate them. i)in woodland, where roots are a problem, the pointer will help you negotiate the roots, so you can just shift the earth where needed, minimising damage to the roots, and time spent. j)they usually have an LED torch [US:flashlight] in them, which is handy in fading light, or in a deep hole Disadvantages include: a)it's one more thing to carry b)and one more thing with a battery that might go flat/get left at home/etc c)they are easy to lose, tread on, etc d)they can slow recovery, due to the 'inching in on the target' effect e)some of them have a beep you can't turn off, which may not always be ideal f)expense g)they won't always find the tiny targets

I understand many modern vehicles have 'cigarette lighter' outlets that are not permanently live, they only energise when the vehicle electrics are on, ie. ignition etc. As this set-up is going to need an 8 hour plus charge, that could be inconvenient. One solution would be to fit a permanently-live socket in your vehicle, or make/buy a free cable socket that croc clips directly to the 12V battery. The advantage of the R/C model battery chargers mentioned earlier is they are fast chargers, measuring a peaking of the battery voltage in order to terminate the charge.

It's a series connection. BUT some of the circuit is powered from one battery only ( likely the audio stage ), so you can't just create an 18V battery and ignore the centre-tap. You may want to investigate using a negative voltage generator circuit, so you use one 9V battery, and 'create' the other with electronics. Obvious starting points would be a circuit based on the ICL7660 chip, or the many similar devices. Or use an oscillator based around a TLC555 timer IC, and add a diode charge pump circuit - this could create either -9V or +18V . Or use one of those ready-made boost-mode voltage converter modules/boards to generate +18V from +9V. All of these methods have one big problem: no On/Off control for the power. Remember the F2 uses electronic switching, part of it is always powered up, but drawing only a few micro-amps ( I've never measured it). Any add-on voltage converter won't use that, so you'll have to put the battery in immediately before use, and remove it straight after. They may also make the supply 'dirty', with AC noise, that may interfere with the detector function.

A bit of Googling turned up this charger, from Powerstream : solar charger These things definitely exist, for the R/C car/plane enthusiasts, so sellers of that type of equipment would be one line of enquiry. The Turnigy C150 looks like it could do the job, input power 12V or mains AC: Turnigy C150 Or the Turnigy Accucell-6 , with 12V only input, and cheaper: Turnigy Accucell-6

I think one thing that has to be considered is the current draw from the battery pack. If you make a longer cable from battery to detector, you have to keep the voltage drop low, by using thicker cable. Your suggestion that two wires are power, two are audio, may be true, it is a simple solution. But only one wire is truly needed for audio, as the battery -ve ( or +ve ) could in principle be used as the earphone ground. This then creates a few other possibilities: Double ground wires for a more solid connection ? Using a wire for digital data transfer to a security chip in the battery, to stop aftermarket battery manufacture? Adding a temperature sensor in the battery would be one way of allowing the battery to be fast-charged ( in addition to the common voltage measurement method ) , this could be connected to a pin on the battery connector, but obviously wouldn't be wired to the main detector. The audio amplifier may be located inside the battery pack, much like the Fisher F75 / Tek T2, and some of Minelab's gold machines. There's also the possibility of future stereo audio, so perhaps two audio wires could come from the detector to the battery. ( Would some type of mixed-mode, or other stereo technique be useful in the prospecting variant ?) As a way of giving me more future options, I would have designed with a 5 pin connector from battery to main detector.

Quote:"I guess the F75 was popular in the US and the T2 in Europe for the same reason" Here in the UK, the T2 was much more popular than the F75 simply because it retailed for 100 GB Pounds ( 125 US Dollars) less than the F75, for what are considered essentially the same machine. On the second-hand market, the F75 suffers greater depreciation, the two machines tend to fetch similar prices. European hunters tend not to be too bothered by modern coins and their ID, so we don't want our ID scales labelled in Eurocent, Pound etc, just remove the nickels'n'dimes stuff. Garrett have got the balance right with this Apex ID : Yank coins for the home market, blank for everywhere else.