DetectingWales.com

I'm building a PI metal detector which I was discussing/expounding on in this thread - just to save going over old ground again:

http://www.detectingwales.com/index.php?topic=24748.0 (http://www.detectingwales.com/index.php?topic=24748.0)

Thought the build may be of some interest to the folks on DW.

Bit of background to the detector I'm building. Having built a couple of detectors from scratch in the past with varying degrees of success, I bought what is supposed to be a working PCB from Bulgaria. I say supposed to be because I've not completed the hardware and therefore haven't been able to test it in any way, but it's *supposed* to be under guarantee anyway.

The Bulgarian connection is interesting because it, too was occupied by the Romans. Unlike the UK where they gradually shut down the operation and made a phased return home, they were apparently forcibly ejected by the Bulgarians, leaving all their villas as they were.

Couple of millennia later and the Romans' houses had all collapsed in on themselves, leaving little to no trace of where they had been. Under the houses, perhaps in cellars, there are alleged to be hoards of Roman gold - but they're out of reach of everyday metal detectors.

That's the story I've been told - I can't agree or disagree with it. But the Bulgarians want to be able to find this supposed gold and went to some lengths to be able to find it - or rather some lengths and breadths. They started using PI machines with huge coils - up to 2 metres square:

https://www.youtube.com/watch?v=f9ck24ibd7A (https://www.youtube.com/watch?v=f9ck24ibd7A)

Now I don't intend using a coil of this size - I don't want to have to use a JCB to dig any finds - so I'll be using a conventional circular coil of about 11". The circuit board I bought is the same as the one used in the video so is capable of supporting different size coils.

I'll post a few pics of my build as it progresses if anybody would be interested?

It will be interesting to see the finished unit I often have a read through the posts on the Geotech forum and know how popular and successful these self-builds are I've thought about making one myself but have to admit the lazy side of me decides not to bother.
Just have to pull you up on the Romans in what was Dacia they were evacuated (thrown out) by the advancing Goths not the native population and this was only the military the de romanization of the civilian population seems (from archaeology) to have been the same as Britain which incidentally was the second from last in and the second out ;)

I'm on Geotech myself - it's a good source of information but things can get a little muddy with all the conflicting input.

I'm hoping to make a decent job of building the detector - I'm fundamentally a metalworker but enjoy making absolutely anything. Some of the skills transfer across to woodworking and other crafts - ultimately it's either hand work or machine work but the principles remain the same.

In my previous builds I've been disappointed with the hardware - I built what would have been a fabulous VLF machine, the 'Practical Electronics Magnum' in the early 90s which worked on the bench but I wasn't able to build a satisfactory shaft  for it. The recommended material was 3/4" plastic waste pipe but it was way too flexible and there weren't many accessible alternatives at the time. I also built a BFO machine before that which was enclosed in a plastic lunch box attached to a brush stick . . .

One of the contributors on Geotech, BernteOne, made a shaft and loop from 16 bar uPVC water pipe, so I tried that for my Barracuda (or Baracuda as they call them on Geotech . . . ) and for the Sniffer (current build) but found it too flexible - the coil  waves around too vaguely to be of any real use.

I'll post some pics of my solution to the perceived problems later.

Thanks for the history lesson - I'm no historian as you can see; I was just repeating the story as it was told to me  ;)

Try fibreglass as used in Radio Antennas and fishing rods : http://www.sandpiperaerials.com (http://www.sandpiperaerials.com)

Lots of different choices, pullwound can also be drilled.

- Andy

You can get carbon fibre tube very light and strong and drillable  i swopped the shafts on my explorer se with 1/2 " carbon fibre makes a bit lighter

I was looking for this earlier when I started this thread - it shows the Delta Pulse 2 detector's depth capability. Just stopped for a coffee and found it:

https://www.youtube.com/watch?v=mvVq2XLSWWU (https://www.youtube.com/watch?v=mvVq2XLSWWU)

The Delta Pulse 2 is identical to the Sniffer XR-71 which I have and is sold by the same company. I make the depth on the tape to be +/- 1.5 metres (five feet in old money . . . )

For my own part, I have misgivings about digging Coke cans at 5' - or anything else for that matter  :-\

                           Using a pulse induction metal detector for general detecting on farmland sounds like a major nightmare in the making. When you first told me about building a PI machine and you weren't into beach detecting I was really puzzled. Now; having heard about the Bulgarian/Roman connection, I can see perhaps where you are heading.

                           As you already know, I used a C-Scope CS4PI on a beach that was used as an air-to-ground target range. Well with all that WWII scrap, eons of maritime scrap, and loads of tourist cast offs, the CS4PI had a great time. The bloody thing drove me crazy! Now that I have upgraded from the CS4PI and my EuroAce to a MineLab Safari, life on the beach has become a lot easier.

                          Recently I drafted in the PI machine to follow up on an interesting Safari find; just to see if the CS4PI was capable of sniffing out anything that the Safari may have missed in the small area where the find with the Safari was made. As happened, it didn't!

                         I'm guessing that it will be a good idea to draft in your pi machine to follow up on major clues in a specific area but await with baited breath to see how you progress.

                         As an aside.... an old friend and work colleague of mine who flew recognisance Spitfires for the RAF said they were told that if they were ever shot down in the Balcones they should surrender to the Germans and not the local military.   :o

No Chris, you've got me completely wrong!! We are only casual beach detectorists, but as I said it's handy to be able to get on the beach when circumstances prevent us from detecting on land! I'm definitely not planning on using the Sniffer to detect on farmland - although I was wondering to myself today what we're missing by not digging iron. First time out in earnest one of us got a big deep signal and spent some time recovering it - it turned out to be a flintlock. Now we have more sophisticated machines we can completely ignore iron (in theory anyway . . . ) and just dig the 'good' signals. But what is a good or bad signal? It's something you want/don't want. I wouldn't mind finding more flintlocks, swords etc . . . Not necessarily valuable items in terms of money, but historically priceless to me.

One thing we have discussed is a ridge and furrow field we have permission on. I won't say we've cleared it of finds but we've pretty much done it to death, and nothing of any real age is coming up, so we wondered whether a PI might reach deeper than our machines do as there must be more history there than we're finding. And it's the next field to the one which produced the Edward III groat and the denarius . . .

My main motivation for building the PI is - because I can. ;) I enjoy working with my hands, making the tools to do a job (see later post . . . ) and using them.

Sorry if I've misled you! Chuckled at the pilot who was advised to surrender to the Germans  ;D

Promised some pics - here they are, with explanations as necessary. Think I'll split them into smaller posts to keep things grouped together.

When I bought the Sniffer PCB I had to decide how I was going to use it - the original Bulgarian Sniffer is designed to be hung on a strap; you can actually buy a kit which includes the box, coil, PCB, battery, shaft (I think . . . ) but I wanted something that was more like a conventional metal detector and all self-contained.  The kit still uses the same control box but it's attached to the shaft and there's still an issue with housing the battery.

I looked at what I had and what I could buy - and it turns out I couldn't buy a box which would house both the PCB and the battery together. I'd already heat-formed the shaft in high pressure uPVC pipe, welded a handle to it, made a hand-grip and decided to mount the controls in a smaller box on top of the handle. The general arrangement is loosely based on my old Eagle Spectrum - 1st pic. But where to put the battery . . . ?

I made a box out of square rain-water pipe and placed it under the PCB housing so it would act as a 'stand' to keep the PCB off the ground and out of the water - see 2nd pic.

This was an ideal position, just under the handle as it caused the detector to achieve a neutral balance - the battery is pretty heavy but the detector handled quite nicely. The problem was that when I picked the detector up the shaft sagged at the ends and the movement of the coil was vague.

So as far as I was concerned, it was a failure and needed some improvement.

The main problem was that the shaft was too flexible - but how to cure it? I had another think about the Spectrum and decided to make the shaft from aluminium tube - if it's good enough for Whites it's good enough for me . . . Sent for a metre of 25mm x 1.6mm aluminium tube from an eBay seller and set to.

This time I didn't set a goose-neck into the shaft, (I do have a hydraulic pipe bender capable of bending 3/4" - 3" steel pipe so could have done it . . . ) opting instead for a straight shaft. I cut a piece of it about 8" long, coped it to fit the main shaft at a 70 degree angle and aluminium brazed it on. See pic.Very strong joint, and quite neat in appearance. I first cut a hole in the main shaft so I could run wires up the handle and into the control box.

Quite pleased with the choice of aluminium - it's strong, rigid and light and I can braze, drill and tap it if I want to. IIRC it cost me £6.60 for the metre length. Thanks to the guys who suggested fibreglass and carbon fibre but this is a done deal now so I'm not going to change it.

While the upper shaft is aluminium, the lower part will be 20mm uPVC high pressure water pipe as originally intended with the MKI design, but since it's so much shorter there's next to no flex in it. As a bonus, I had already bought a 25mm - 20mm reducing compression fitting in plastic which still fits the 25mm upper shaft and after I bored the internal stop out in the lathe allows the shaft to telescope for adjustment.

Ah ha, I stand corrected. Got ya now. :)

                     Looks like some very interested projects that you have in hand and I hope to see the fruits of your efforts real soon.

                     I often wonder about ignoring iron signals and when I first started detecting I dug pretty much everything. I believe that a lot of really good finds and hoards are found by beginners. They still have that "ooooh I wonder what this is?" freshness about them. Dave, an other caravan resident on our park, dug a lump of iron from the dunes and got himself a WWII hand-grenade! :o  He also got himself a rocket for digging in the dunes!  ::)

                     Looking forward to watching your progress.  ;)

So now I had a viable shaft. Next I needed boxes to house the PCB and battery, and the controls.

I laid the PCB and battery on a sheet of paper and tried different arrangements until I had one that looked right, then when I knew what size the footprint needed to be I made a development so I could order the aluminium sheet.

I needed a sheet metal folder to make the box - which of course I didn't have. Looked at Machine Mart, eBay etc and decided to make one. I have an extensive pile of what my wife thinks is scrap from my days of contracting in engineering, so once again had a look what I had and how I could use it to make a folder. I've used them before in the dim and distant past but never took that much notice of how they were made, so I made it up as I went along.

The pic shows how it turned out. The main body is a chunk of rusty 3" x 3" x 3/8" angle, the movable 'jaw' is a length of 65mm x 65mm x 4mm steel box section with a flat plate welded to it and the handles are a half-shaft off a car. It's not pretty but it works and will take a piece of sheet up to 18" wide. I tried it on 16g steel sheet and although I broke a sweat nothing broke on the folder.

OK - I'd got the aluminium sheet and I'd got the folder. Now what . . . ? It had been many years since I'd used a folder and I only had one chance at it so it had to be right first time.

If you'll refer back to the photo of the Spectrum you'll see the form my box was going to take, with the 'base' attached to the shaft and the 'lid' underneath. With this arrangement, any rainwater will run right off without getting in with the electronics. I had a bit of a practice on some offcuts from the sheet and started making the base - see 1st pic. Turned out great (in my humble opinion . . . ) so I brazed the mitres on the corners to add strength and keep water out.

The lid has to be a neat fit inside the box, which is why the use of the folder was so critical. As you bend metal, one face is being stretched and the other compressed, and the radius of the bend eats up *some* material. Could I remember the formula? Could I ****! So I resorted to empirical methods and did a couple more trials on offcuts which told me how much narrower my scribed lines were to be than the finished box.

I'm pleased to say that it's a good fit, as I wanted, but have to admit it was probably more luck than judgement . . .
The result is in the 2nd pic.

The 3rd pic shows the completed box (in need of fettling) and the 4th shows how it will go together on the shaft. It's just sitting there for demonstration purposes at the moment so its position isn't yet fixed - depends on the balance.

That's as far as I've got up to now, but I'll keep updating this thread as and when I get anything done.

Interesting read Cymro, can't wait for the next instalment

Thanks, Dryland. It's a bit of a voyage of discovery for me - I do have a plan in mind but things tend to get made up as I go so it may evolve further yet . . .

I've discovered that some users have added a meter into the mix, but I'm still trying to work out whether there would be any advantage in having one. You can see some in the Delta Pulse 2 videos on YouTube. The PCB has the capability built in - I wrote to the Bulgarian seller who told me where it connects to. The ones I've seen are LCD bargraph panels  which presumably display the output from the VCO - i.e. a stronger signal gives higher tone audio output. The best way I can think of doing that is using a microcontroller like an Arduino or a Raspberry Pi, but although they're relatively small they still need space in one of the boxes somewhere . . . And power.

Remember the old PCs which used to down tools for a while and display a message saying, 'Thinking . . . . . . ?'

That's me right now!

Talk to Woodbob - he's made a few detectors recently and is also on the Geotech forum

Thanks - will do!

Would be happy to help and exchange ideas on PIs I'm in Newport not sure where you are.
 Also built the Magnum but didn't use it much and came back to the hobby a few years ago and as has been mentioned PIs don't miss a thing as many are designed to find very small pieces of gold in OZ and USA they sure do seek out every piece of iron and rust particle.
 I would suggest building one of silverdogs kits, before getting too advanced there is another the MPP which is an improved version of one of Eric Fosters design, not for the inexperienced

Ta for the reply, woodbob123 - PM'd you.

Right then - it's time for the next instalment of the PI build.

I wanted to make a solid job of the hardware, and another potential weak spot was the connection between the control box and the shaft. It would have been easy enough to chuck a couple of self-tapping screws through the box and into the shaft but the box which houses the PCB also houses the sealed lead-acid battery which is fairly heavy.

What I wanted was a connecting piece which would saddle the tube of the shaft and have a substantial flat base which I could drill and tap into - machine screws are less prone to working loose than self-tappers. I do have reasonable workshop facilities but I lack the one machine tool which would have made the piece in half an hour - a milling machine.

What I do have is a small foundry setup, so I set to and made a wooden pattern for the saddle piece - see 1st and 2nd pics. One reason it's taken me so long to get to this stage is because I needed to paint the pattern so the sand didn't stick to it - and paint takes its own sweet time to dry. Couple of coats of emulsion, sanded between and after coats, four or five coats of acrylic aerosol car paint, couple of days for it to harden . . . Soon mounts up. Then there's the weather - don't want to go pouring molten aluminium in the rain or you might just get a face-full as the water flashes to steam and expands at a rate of knots . . .

So one way and another the first day I had that was predicted to be dry all day was last Saturday. It took me most of the morning to prepare everything, then I rammed the pattern up in the sand and lit the furnace. Any odd bits of aluminium went into the crucible - an old mitre saw frame, bits of alternators, lawn mower engine - anything . . .  Took about 20 minutes for it to melt, then I poured it. Pic 3 shows the flask just after the pour, then Pic 4 shows it after I'd shaken most of the sand off it - I like to leave it about as long as it takes to make and drink a cup of coffee before I open the mould . . .

When it was cool enough to handle I sawed the sprue (the big mushroom-shaped bit) off the casting(Pic 5) and tried it against the tube. The saddle part was a bit too tight so I had to hand fit it with a half-round bearing scraper until it was just so, then trued up the remaining five sides  on the shaper (Pic 6.) Couple of hours hand work with the scraper and half an hour on the shaper got the job done.

All that was left to do then was to braze the saddle piece to the shaft (Pic 7) so I can attach the PCB box - just finished brazing it an hour ago and I'm calling that it for today. Pic 8 shows how it will fit on the box.

It looks like this part took a lot of effort for not much reward - it might even be said it's over-engineered - but I'm trying to eliminate any weak spots in the design. If I ever want to make another piece like it I'll have the pattern on the shelf ready - and making the pattern is the biggest part of making the casting.

Next up is deciding how I'm going to make the control box which sits on top of the handle - I'll update this thread as I make progress.

I know I said I was going to make the control pod next but I'm stalled on that while I consider whether to include a meter or not, so I made the arm-cup instead. It all has to be done and it doesn't really make much difference which order it's done in.

I'm sure you all (both . . . ?) remember the casting I made for the control box mounting? OK - since the biggest job in any casting is making the pattern, I cast another for the mounting block I intend to hold the arm cup. Just a case of ramming it up in the sand, melting the metal and pouring now that I've got the pattern.

When it was cool enough to handle I sawed it in half, machined it all over in the shaper then clamped the two halves together and mounted the whole issue in a 4-jaw chuck in the lathe. Bored the inside to fit over the shaft tube and faced both ends - 10 minutes work (or 30 if you include centering it up with a clock gauge . . . ) 1st pic.

I then needed to make the actual arm cup. I used some 1mm aluminium sheet I had lying around - cut 2 the same but drilled 1/2" holes in one of them - pic2.

Brazed through the holes so they became one piece, chain-drilled and filed the slots for the strap and then formed it into the shape I wanted on the folding jig I made at the beginning of this whole epic story. I say 'the shape I wanted,' - what I actually mean is the shape I could make with the tools I have. Whatever. Pic 3.

I drilled the arm cup, then drilled and tapped the upper mounting block for M5 pan-head socket screws to hold the arm cup on. Not much to see there so no pic. I also drilled and tapped the same part for an M6 thumbscrew (yet to be made) to hold the whole thing to the shaft. Again, no pic.

Waste not, want not. My mother dinned that into me as a child and it's stuck. I had the sprue  from the casting I'd made for the mounting block lying around. I'd normally put it in the crucible to re--melt next time I fired the furnace up, but it was a roughly cylindrical shape if you squinted at it in a certain way . . . Pic 4.

Sawed both ends off and mounted the middle bit in the lathe - a few minutes later it looked like Pic 5.

Knurled it for a finger-grip, drilled and bored it to accept the head of an M6 bolt and started parting it off - Pic 6.

When it was off the lathe I put the head of the M6 bolt in the recess, clamped it in place and aluminium brazed it in. The filler rod I'm using won't adhere to steel but it will to zinc - and the bolt is zinc plated . . . Pic 7.

When it was assembled to the arm cup mount it was as you can see it in the 8th pic, and I placed the shaft, with the arm cup onto the control box to show how it will all look in the 9th pic.

I've been thinking about how I'm going to mount the PCB and the battery, so I think I might make that my next mission before I make the control pod. After all that's done, *all* I have to do is to hook everything up and finish it all off - paint etc.

It's certainly getting there have you thought how the metal upper section will effect the coil field?

Massive respect for your fabrication skills...... I was also wondering how the metal would effect the function of the detector?

Me thinks you must have been an alchemist in a previous life!  :)

Hi Geoff - I'm hoping that all the metalwork will be far enough away not to affect the coil - it would do if the shaft was vertically above the coil but as it will be at an angle it should be out of range since the field of the coil *should* be at right angles to the plane of the coil.

Looking at the PI machines out there commercially they all seem to use the same arrangement, and a friend actually did an experiment with his machine which seems to bear this out.

Fingers crossed . . .  :)

Ta to Nobby and Resurgam for the heads-up - nice to have some feedback on my efforts! I've been wondering if anybody was actually following the thread . . .

"Following this thread" ? I can't wait to see he finished article lol.. As Nobby said it must be wonderful to have the skills and the know how to be able to turn your hand to something like this. If the Whites XLT etc is anything to go by, I think you should be ok as far as the upper metal section affecting the coil, but I speak as a complete novice in these things.
                   Just a thought but  Whites use a carbon fibre lower shaft to lighten the detector, Have you given any more thought as to the final weight of yours ?

Hi Dryland - thanks very much for taking such an interest in my project, and for the complimentary remarks.

Have to confess - I cheated . . . I did this sort of thing for a living for 25 years so I'm not a complete tyro at it. Got made redundant in my 40s cos no-one wanted those sort of skills (it was cheaper in Taiwan/India/China or somewhere . . . ) but it gets in your blood. I'm lucky that it's also my hobby nowadays - I set up a decent workshop years ago and I'm always on the lookout for opportunities/excuses to use it.

As you'll know, the design of the machine is a straight steal from my old Whites Eagle Spectrum which was a heavy machine to begin with (even more so after a previous owner changed the 'C' cell rechargeables for 'D' cells . . .) but the balance is good.

The heaviest part of this machine is going to be the battery - it's a sealed lead-acid one because PIs are power-hungry. I deliberately haven't fixed the position of the control box yet so I can experiment with it to get the best balance I can. If you can't do anything about the weight at least you can make sure it works with you rather than against you . . . The rest of the metalwork isn't that heavy.

Hey - who knows; if this works out maybe I'll get a queue of people wanting bespoke hand-built metal detectors . . .  8)

                            Following you all the way and looking forward to when you run the beast over a wet salty beach.  :)

                           As an aside, I noticed Geoff's comments about the possibility of the metal structure interfering with the coils magnetic field from above and I set to wondering if the magnetic field from a coil can be induced to be directional like some short wave radio aerials. ie.......big magnetic field below the coil and minimal magnetic field above the coil; or the magnetic field above the coil deflected back down to strengthen the lower one?  :-\ 

Interesting idea about a directional coil . . . I passed the Radio Amateurs' Exam 30 years ago (never got licenced though . . . ) and what you're describing is a beam antenna. It uses a driven element (which is connected to the radio) with parasitic elements - a reflector behind it - which acts just like a mirror - and multiple directors in front. They're arranged on a logarithmic scale IIRC and the calculations would make your eyes water. Together they produce forward gain by preventing the radio waves from going in all directions as they naturally would from a single vertical (or horizontal) wire and focusing them in the direction the antenna is pointing. That's what a TV aerial is and does.

The size and spacing of all the elements is dependent upon the frequency you want to operate on - the higher the frequency the smaller the elements - that's why you see huge arrays outside Hams' houses if they're working (say) the 11-metre band (that's 25 - 26 MHz) and much smaller ones if they're on 2 metres (144 MHz-ish. . . )

You can make the antenna smaller by using a fractional wavelength - say 1/2 or 1/4 wave but at cost of efficiency. I'm not an antenna designer so there are probably (make that definitely) some tricks I've missed . . .

When you consider that the PI I'm building runs at 100Hz you can see that the coil would be . . . ummmm . . . cumbersome. Even for your CS4 running at 17KHz it would need to be massive. Interestingly, the Sniffer I'm building is designed to use big coils - 1 metre square or even 2m x 1m - the 280mm plain loop I intend using is inferior to their depth but you have to balance that against usability.

Thanks for following - it's good to know folks are interested. If it eventually works I'll let you have a play with it . . .

Fantastic job with the casting what I use to make up shafts is much simpler not having a furnace etc (wife wont let me) using standard Ali tube turn down a plug of plastic 1-2" long to a "tap in fit" tap it down to where the strength is needed then either fix it with a couple of self tappers or make up a "swaging tool" by removing the cutter from a pipe cutter and replacing it with a rounded blade and running that around to force Ali into plastic. I use this method a lot when making telescopes and stuff. Hope that makes sense. Once fixed it can be drilled through with no danger of crushing the tube however much you tighten the bolts.
If you use plastic pipe for stem it can be made much stronger by wrapping with the epoxy bandage they use to make lightweight casts for broken arms available from e-bay in black looks a little like carbon fibre from a distance and can be painted.
Cymro I've sent you a pm.      Bob

just a thought for a shaft......Val Beechey has some bamboo for sale :D :D :D

Thanks ;)

The foundry is quite a recent addition to my armoury - did my first casting in 2011. Back in the 1990s I became aware of a series of books by an American author, Dave Gingery, called 'Build your Own Metal Working Shop from Scrap.' I finally bought them in about 09 and devoured every word. His premise was that by making your own castings from scrap aluminium and fitting steel sliding surfaces you can build a set of machine tools. So the first book shows how to build a charcoal-fired crucible furnace and make castings, in the second book you use the furnace make the castings to build a lathe. In the third book you use the furnace and the lathe to make a shaper; in the fourth book you use the furnace, the lathe and the shaper to build a milling machine etc. Book 5 is a drill press, book 6 is a dividing head and other accessories and the 7th book (illogically) shows how to build a sheet metal folder.

Built the furnace but was unhappy with the time it takes to melt aluminium with charcoal so made a propane burner. Much better. Already had a lathe - not worth building one so decided to build the shaper as a first project. Made most of the patterns and was waiting to start casting them when I was offered a commercially made shaper for a pittance. No brainer - I bought the shaper and rebuilt it from the ground up. Started making the patterns for the milling machine instead but bought a small (2" x 10") lathe off eBay from a seller in Brum. When I went to collect it the guy said, 'Oh, yes - this goes with it too  . . . ' When I got home I discovered that 'this' was a beautifully made Gingery milling machine. Couldn't make it up ::) I've already got an Elliott drill press so don't need to build one, so there's only the dividing head left to do.

I can understand your method of making your shafts - as I've said mine is probably over-engineered but it works for me. Good job I'm not trying to make money out of it - it would cost a fortune! I did try the plastic lower shaft in the aluminium upper shaft - I had a coil fitted to it to give it some weight and it seems stiff enough as it is - when I built the Barracuda I planed a long, thin piece of wood down to make an internal 'spine' in the plastic pipe which stiffened it up. The upper shaft was the problem as it 'hogged' in the middle where the handle was hence the reason for the MK2 aluminium setup.

Think I'll christen this machine 'The Vincent,' - Vincent motorcycles were once described as 'a set of solutions to non-existent problems . . . ' just need someone to make the vinyl stickers for me  ;)


Don't think I wasn't tempted . . .  ;)

Been busy in the workshop again - working on the main PCB box now.

There are only two components inside this box - the PCB and the battery. The last thing I want is for a heavy sealed lead-acid battery to break loose and destroy the PCB, so I needed to make a good solid mounting for the battery.

Couple of problems there. The battery needs to be at the forward end of the box, which is also where the wires from the PCB to the handle-mounted control pod need to exit the box. I also didn't want the battery terminals to be able to short-circuit on the aluminium box. I wanted the terminals at the top in the operating position - although it's a sealed lead-acid battery there is the minute chance that it might leak acid from the casing onto the PCB if it was upside down - and the most likely place for that to happen would be where the top of the battery is fixed to the bottom.

I had the additional problem that the bottom part of the PCB box has a lip about 1/2" deep which fits inside the upper part, so the battery compartment couldn't be allowed to sit flush against the end panel - it needed a stand-off.

I used some thin (1mm) aluminium sheet I had in my stock of 'useful one day' metal so I drew up a layout for a folded box, marked it out on the aluminium and cut it out (Pic 1.) Folded the lip for the front and the back in Pic2  then folded the sides up into the box shape in Pic 3 and brazed the mitres in the corners then cut a hole in what will be the top for the terminals to protrude through.

I still had the problem of the lip in the bottom part of the box, so I had a root around and found a bit of 4mm flat aluminium plate, which I bandsawed a suitable chunk from and drilled and countersunk a couple of decent sized holes in it (Pic 4.) I clamped it to the battery holder and brazed it on - Pics 5 and 6.

When it was cool enough to handle I drilled and tapped four M4 holes to attach it to the box - pic7. It's bolted to the box in Pic 8, and Pic 9 is the same view with the picture rotated so it looks as it will in use.

Its position means that I have enough space to run the wires under the battery through a hole (yet to be drilled) and up the handle. The battery will be held in position by the bottom part of the box, but I may yet attach a Velcro'ed webbing strap under the base of the battery to hold it in place if I remove the bottom of the box.

I've attached the PCB/battery box to the shaft with M6 button-head socket screws now that the battery is firmly attached - I wanted to find the best point of balance with a coil and the arm cup fitted.

Going to have to decide how I'm going to mount the PCB in the box soon - oddly, there aren't any holes in the PCB and it's double sided so I can't drill any. It needs to be mounted in the same orientation as the battery - component side up in the operating position - to help with routing the wires. I could use PCB stand-off clips but I don't want any holes in the top of the box to let water in. Got an idea about how I'm going to do that - I'll explain in due course.

What do you reckon the whole thing will weigh, when finished and assembled? 

Don't know offhand - I'll try and weigh what's already there tomorrow - all that's missing now is the control pod. The balance is good though - I think that's important.

The coil I put on is off the Barracuda - haven't tried the proper coil on it yet (read: haven't wound the proper coil yet . . .  ;))

                       Having been with you from the commencement of this project; it's interesting to see how serendipity is greatly on your side!  ;D

Well Chris, I'm trying to eliminate luck from the equation by breaking it down into steps and planning each step as I go, anticipating potential problems. Sometimes you can't so then you have to work with what already exists.

As I've said this is a learning experience - not the materials, skills or techniques but what will work best in terms of a functional unit - and one reason why I chose to base it on an existing successful design.

Just weighed it and it crashed the digital kitchen scales . . . Seriously - the scales have a limit of 2Kg and they showed 'OVERLOAD . . . ' So I took the battery out and weighed it separately - the battery is 560g and the rest of the detector weighs 1.625Kg, making 2.185Kg or 4.75 lbs. Shouldn't be much heavier when it's finished.

Just hope the PCB is in working order when it's all done . . .  ::)

                                    Once you have it all together and up and running; if you find you have need of a bungee harness, I have a spare one going free. Just pm me and it's all yours. :)

That's kind - thanks!  ;D

If you're in the area and would like to have a look at what's going on, you're always welcome!

                                   Sounds interesting m8; I should be down that way in the next week or so. Having run some of my finds by the Crown Estates and the FLO and both having relinquished any interest; it just remains to run them past local Plod and the Receiver of Wreck. Not to mention the RAF Historic Section.

                                   Things are starting to get interesting at Talacre; if not a little strange! I chose beach detecting as the easy option but hadn't counted on having to contact the Plod, Receiver of Wreck, Crown Estates, RAF Historic Section, and the FLO. It would be interesting to see you run the new detector over the sands at Talacre and see what you can winkle out. Hopefully nothing for the UXO squad!  :o

                                   Do you have any idea of a construction completion date for the new machine?

Good luck finding any Plod around these parts - it's bandit territory! We're pretty much reduced to PCSOs these days since they sold the Police Station - they maintain an office at the Town Hall but when I wanted to report something the dopey girl on reception said I'd have to make an appointment to see them  ::)

Seem to have plenty of time for their Arrive Alive vans though . . .

The detector is getting done in fits and starts between actual detecting sessions and whatever else is demanding my attention at any given time. I tend to mull things over for a bit to allow my brain to evaluate the next problem and find a solution to it so it's difficult to make any promises on a completion date.

Is 'sometime sooner or later' helpful . . . ?

I'll email you my contact details.

If you don't mind me asking why haven't you gone the lithium battery route to save weight?

Well done for all the effort, and technology,know how,tenacity of purpose, dexterity, but for the likes a me......Naa !! I still think I'll be staying with CRAWFORDS !!!LOL!!!👏👏👏👏👏👏👏👏 👍

                        I emailed North Wales Police and they said that the nearest police station for reportage of finds at Talacre is Rhyl.  :(

Don't mind at all. Simple, quick and honest answer is that I hadn't considered it . . .  :)

After your suggestion I trawled eBay for a while and two things struck me: most of the lithium batteries on there seem to be dedicated - rechargeable drills etc, and the ones which aren't seem more expensive than SLA.

But I've got a SLA battery, have mounted it and find it's not so heavy after all, so I won't be tempted to change it.

Thanks for the suggestion though - maybe next time . . .  ;)


I enjoy making things - any things, so for me it's more the journey than the arrival IYSWIM. There is a lot of satisfaction in using something I've made myself as well, but I can appreciate your point of view.


Yabbut - I'm not in Rhyl . . . Out in the boondocks where I live (Holywell . . . ) they have to send bobbies from Colwyn Bay if there's any crime - but of course there is no crime here . . .  ::)

Well if you want to change it in the future then this is what to look for...
http://www.amazon.co.uk/Enjoydeal-Portable-6800mAh-Rechargeable-Battery/dp/B00V68AQL8/ref=sr_1_8?ie=UTF8&qid=1444593456&sr=8-8&keywords=12v+battery+cctv (http://www.amazon.co.uk/Enjoydeal-Portable-6800mAh-Rechargeable-Battery/dp/B00V68AQL8/ref=sr_1_8?ie=UTF8&qid=1444593456&sr=8-8&keywords=12v+battery+cctv)
These only weigh a few ounces but as you can see it 6.8 Ah so would last 5X the length of time than the acid battery

If you need Police, then we've got plenty that you can have.

So that's where ours have gone . . .  :-\

 ;D ;D ;D

we need more of them here to keep an eye on dryland ::) ;D

After a lot of soul-searching I finally decided that I could do without a meter on the PI machine - I'm pretty much resigned to the fact that I'm going to have to dig everything anyway.

Had a look at what I needed to accommodate and fixed a size in my mind - there are six control potentiometers and at least two LEDs so it was never going to be small . . . I also decided on a modular form of construction so if I do change my mind about the layout, size etc I can just change what needs changing rather than starting again from scratch - in fact the whole detector has evolved on that principle.

Having decided on a size and vague shape for the control pod, I had to decide how to attach it to the handle in line with the modular approach, so I hit on the idea of a tapped mounting pad which everything else fits onto.

I've actually added numbers to the pics this time - hope it helps to follow the build.

Started off with an offcut of 1.6mm aluminium sheet and cut it out as shown in Pic 1, then just gently 'broke' the lines of the horizontal bends (Pic 2). Folded the edges fully and 'persuaded' the folds I'd broken with a dolly and soft hammer (Pic 3). This part will form the back and bottom of the pod and will be screwed in place on the mounting pad.

I had a chunk of cast aluminium I'd made for another job (I'd used an open mould, using a builders' mastic tube as a pattern - more on this later . . . ) so turned it to size (Pic 4), bored it to 25mm (Pic 5) then cut a piece off, marked it for 3 holes and drilled it ready to tap it M4 for button-head stainless screws (Pic 6.)

I then parted off two discs from the piece I'd drilled, tapped the one in Pic 7 with the marking blue on it and drilled clearance holes in the unmarked disc. Since the holes had been drilled in both pieces while they were still attached to each other they had no choice but to line up and couldn't cause me any problems due to mis-alignment  ;)

I then brazed the tapped piece to the handle, which is attached to the shaft (Pic 9) after which it was just a matter of cutting a hole in the bottom of the box and drilling the circle of holes around it (Pic 10,) then screwing the pod to the mounting pad in Pic 11.

Obviously I need to braze the corners of the pod base and do some more finishing off, then I have to make the front and sides for it - that's for a later installment.

Just in the interests of assuring my loyal readers that things don't always go according to plan, Pic 8 shows the deliberate(!) error I made. I'd made the mounting pad and its securing ring from some cast round bar I'd poured in the past. Unless I'm melting a known alloy, I'm never sure exactly what goes in the crucible. Anything crucial and I'll try and use *say* alloy wheel material (or 'wheelieminium' as we home founders have it . . . ) or pistons etc.

When I came to braze the mounting ring to the handle section, just as the rod started to flow, the ring melted. I was in a bit of a quandary so re-heated it to melt the rest of it off, filed the handle smooth and re-made the ring out of some expensive aluminium billet I'd been keeping for a special job. No idea what special job - just 'special . . . '

Also, since I'd used an open mould it didn't have sufficent hydrostatic head to exert enough pressure to consolidate the alloy when I poured it, leading to a lot of entrained air bubbles which can be seen on the surface of the bar in Pic 4. (Weakens it . . . )

Been a bit slack with the pics lately - also been busy with a plasterer's trowel trying to get the hall finished (only started it in 2000 . . .)

The PI I'm building has a 'Reset' button which has to be pushed every couple of minutes (or so they say . . .) and indeed I had one on the Mk1 version I built. I did the best I could with positioning it but it was only ever the best of a bad job. The pod it was mounted on was 135mm wide and it had to go at one side or the other - whichever side I chose was a good stretch of the thumb, so since I'm left-handed I placed it on the left-hand side. A right-hander would have had problems . . .

So, again taking my inspiration from my Whites machines, I decided to use a 'trigger' right behind the handle. I sketched up a small box to put the centre-sprung switch in, cut a piece of aluminiun sheet to suit and cut it out (Pic 1.) I carefully folded it to shape, which wasn't easy as it's small enough to cause problems getting it in the folder (Pic 2.) I then made a cut-out in the fascia mount and brazed it in place (Pic 3) at the same time as brazing the seams.

Next job was to make a handle grip - I had already brazed the pod mounting in place on top of the handle so couldn't slip a bike handlebar grip over it, and couldn't have done that first in any event because it would melt under the heat.

There is a mouldable plastic material available - called Sugru - which would have been ideal for the job but costs a bomb to buy. I used a recipe I found a couple of years ago for a Sugru substitute, but at hardly any cost. It uses silicone builders' mastic mixed with cornflour and gives a tough, resilient plastic material. It works because the catalyst for the silicone is water, but the silicone forms a skin quite quickly from the moisture in the air so takes ages to cure all the way through cos the skin prevents it from absorbing any more moisture . . .  Cornflour is hygroscopic (absorbs moisture) and so when it's mixed with the silicone it carries the moisture all the way through with it. It takes a bit of mixing up but once it is it turns into a Plasticine-like consistency which can be moulded by hand and hardens fully in about 20 minutes.

 I bought black mastic, otherwise it can look somewhat 'medical' in a sort of white translucent finish. It's possible to add a tiny bit of gloss paint to colour it - but it stinks of paint for days if you do. I used some artistic licence and moulded finger-grips in, using diluted Fairy Liquid (TM) to smooth it out and prevent it sticking to me. The result can be seen in Pic 4, along with the trigger switch for the 'Reset' function. A word of advice if anybody wants to try using this for anything - there are two types of mastic; silicone and acrylic. Only the silicone will work, and you can tell them apart because the silicone has a strong smell of vinegar as it cures (and should say 'Silicone' on the tube . . .  ::))

I then sketched the fascia panel for the pod, cut it out from sheet, folded and brazed it, forgetting to photograph it as I went. It was only after I had marked it out and drilled the holes for the controls that I remembered to do it. It's nothing new, just using the same procedures as before. The result can be seen in Pics 5 and 6.

I've painted the shaft today, using Plasti-Kote Satin Black aerosol paint and it's drying as I type. I intend painting parts as I finish working on them from now on - I'll probably have finished with the fascia tomorrow so that can be done too.

Will post more as it happens - I'm looking to order electrical wiring connectors now as I'll be ready to start wiring it soon. I want to have the fascia detachable by having a multi-way plug and socket inside the box - bit expensive but I've got this far . . .

            Nice progress Clive. Having hade the opportunity to meet your brainchild, hands on so to speek; the things that impressed me were the balance and the initial comfort of the hand grip. It just fealt right.

Thanks, Chris!  ;)

I've never heard of the silicone and cornflour mix before, Great tip that might come in handy one day.

I can't claim any credit for it; I found it on one of my favourite hackers' sites, Instructables:

http://www.instructables.com/id/How-To-Make-Your-Own-Sugru-Substitute/ (http://www.instructables.com/id/How-To-Make-Your-Own-Sugru-Substitute/)

There are 15 steps in the Instructable - you'll have to follow the 'Next' button to access them. Or register for free and download the PDF.

I guess you could use anything which absorbs water to mix with the silicone - I found a YouTube video where someone used baking powder.

Knowledge is power . . .

Could be a longer job than I thought - for all the wrong reasons.

I sprayed the shaft and a few other bits and it's taking a dog's age to harden. Says on the tin that it's touch dry in a couple of hours and fully hardened in 24 hours.

Still scratching really easily 48 hours on . . .  :'(

Stick it next to the radiator.....been using plastikote today and no problems, its one of the better ones ive used

Your reply gave me a laugh - I could put it next to the radiator but we don't put the heating on unless it's freezing outside! LOL

Never used it before so believed what it said on the tin . . .  ::) Although the weather for the past couple of days has been mild but dank, so maybe that's affecting it. It's in the Woodwork Dept (outside shed . . .  ;)) to dry, and there's definitely no heat out there!

Been waiting and waiting for the postman to deliver the electrical terminals I sent for from a couple of eBay sellers. Finally got fed up yesterday and checked my eBay purchase history just in case . . .

Oops - senior moment. Placed them in my 'basket' but forgot to check out . . . So I'll have to wait a bit longer for them.

Meanwhile the paint is disappointing. It was applied more than a week ago and if I place the painted bits against anything it sticks and the paint peels off. Oh well, it's only cosmetic . . .

A question for anybody who's following this; do 'we' know anybody who has a vinyl cutter who could make some decals on the cheap? Just a bit of fun (and a bit of vanity . . .  :))

                      As an aside, and having seen the project, I was impressed by the initial comfort and balance of the machine. That set me thinking and I wonder if the many complaints I hear about the weight of some machines is as much to do poor balance as it is to do with weight. What do they call it; poor ergonomic design?

Thanks for your favourable comments, Chris.

It mostly comes under the heading of taking that extra bit of care. The machine is on the heavy side but with a bit of careful placement it becomes more manageable - it feels like I could swing it all day with no ill effects.

Manufacturers could do the same thing but are possibly disinclined to do so - maybe it's more cost-effective to build them in a certain configuration? Perhaps if they were designed by actual hands-on detectorists they could improve their products even further based on experience of what is usable and what is not.

Following on from that, I'm looking for a larger coil for my DFX; these have a reputation for making the machine too heavy but in the light of your comments perhaps adding a bit of extra weight elsewhere to improve the balance would be a viable option?

                  I got the feeling that any weight was taken up in a direct line from shoulder to elbow and the wrist and forearm would be just all that was required to facilitate the swing, Did make me wonder if fixing a counter balance to an existing detector would make for easier swinging of the said machine. Of course one can always use a bungee harness.

Been busy with other stuff but still managing to do a bit. What with the time the paint is taking to harden off I really needed to finalise all the work on the main control box so I could paint it and leave it to dry for a couple of days before I tried to assemble it.

Pic 1 shows the PCB I bought off the Bulgarian. What's missing? Holes . . .

This meant that I couldn't screw it to the box in the usual way, so I had to find a workaround. I could have used plastic stand-off pillars but I would have had to drill holes in the uppermost surface of the box, which would have let water in. Thats a Bad Thing.

The two sockets on the left-hand side of the PCB in the photo needed connectors - to be fair it did come with some but they were just a row of pins going through a plastic strip. I didn't like that so I bought some right-angled ones, which I soldered to little bits of Vero board - it's perforated phenolic PCB material with a matrix of holes and copper strips. The connecting wires could then be soldered to the Vero too and turn the connection through 90 degrees, keeping them away from the box - Pic 2.

I decided to turn some small threaded aluminium buttons (Pic 3) and braze them to the box. The register on them is to fit into holes in the box which were then brazed from the outside, sealing the holes against water ingress.

I also made some bobbins from some black nylon round bar (Pic 4) which would grip the PCB and not conduct a current.

 As a belt and braces measure, I also brazed three of the buttons from the inside (Pic 5.) Unfortunately the heat from the brazing warped the box a bit and I had to spend some time with a soft hammer and a dolly to straighten it out. I'm no panel beater so it's less than perfect, but it's as strong as hell . . .

I then screwed some M4 brass studding into the buttons (Pic 6) and then added plastic spacers and the bobbins (Pic 7.)

Finally, I could fit the PCB (Pic 8,) and have it securely supported in an inverted position as I had wanted.

I've now sprayed the control box and an (im-)patiently waiting for it to be hard enough to handle.

We await the final countdown, with baited breath.

Was going great guns this afternoon until the visitors arrived. I was working on the control pod, then came that ring at the doorbell. They've just left so I'll get no more done today; off with the detector at low water in the morning so *maybe* I can get a bit done in the afternoon.

Getting quite excited about getting it finished now, I've more or less finished in the PCB housing; got it all wired up and fitted the connector for the coil lead - just got to wind the coil and get the pod wired up and I can switch on for a trial.

So near, yet so far  ::)

Hurry up I'm getting impatient   ;)

Hush. More haste, less speed!  ;)

LOL

So am I - but it's a thing that won't be rushed.

I've mounted PCB headers inside the pod to keep it all tidy and so that it doesn't turn into a bird's nest in there, but putting the pins on the plug ends of the wires is incredibly time-consuming and fiddly. It even surprised me . . .

Added to which my daughter's car has demanded my attention so I've been dodging downpours but have had to admit defeat and book it into a diesel specialist. I'll have to limp the 20 miles there on two cylinders (of three . . . ) and get the bus home. That's the morning gone right there . . .

I'll try and get some more pics up soon for my loyal fan-base  ;)

Finally got some progress to show for the impatient among us . . .  ::) Since the weather was solid rain most of the day I lit the wood-burner in the workshop and settled down to getting it done, and I'm quite pleased with it so far.

I wanted to get the control pod all wired up so that I could draw a line under it and start on the coil, which should just about finish the build. I've been going cross-eyed trying to get all the terminals onto the various wires so that if the unthinkable should occur I can just unplug the parts and fix whatever problem it was . . .

Firstly I had to find some way of mounting the speaker - I was lucky enough to find a 40mm mylar unit on The Bay for a reasonable price. Didn't want to bolt it in so I bored some extruded aluminium bar to make a housing, brazed it to the pod back-plate and drilled holes to let the sound out - Pic 1.

Next I wanted to make up a circuit to indicate low battery voltage by means of a red LED - the green one in Pic 2 is to indicate that the detector is switched on.

I mounted all the potentiometers in the pod cover, wired them up and installed the indicator PCB I'd built earlier - Pic 3.

Pic 4 shows the terminal housing which connects to the pots in the cover just prior to attaching it to the back-plate. The gubbins to the left of the terminations are the charging socket and fuse while the one to the right is the headphone socket.

Pic 5 shows the fascia of the control pod after everything was installed.

Pic 6 is the underneath of the pod showing the headphone socket from the outside, and Pic 7 shows the charging socket and fuse.

Technically there should just be the coil to do to get the detector finished, but Murphy's Law will no doubt raise its ugly head . . .

Well, it's looking good.

Proof of the pudding . . .  :-\

I know, I know; but if you are not totally pleased with it's detecting performance, it looks as though you will be able to listen to Radio Luxembourg on it!   ;D

Will you be having it's maiden outing videoed?

LOL'd at Radio Luxembourg  ;D Showing your age a bit there, Chris!  :) Wasn't it on 208 . . . ? I remember my Dad used to yell at my elder sister to turn it down when I was a kid (and then at me when I was older . . . )

Listen, I'll be a happy man if it does anything after all this - it'll be a bonus if it even turns on . . . As for videoing it, I'm not sure how much humiliation I can take!

                                      70+ to be exact! Oh Ho, and I remember Dick Tracy special agent, PC49, Dan Dare, and Journy into Space. Sometimes have trouble remembering why I came into a room though.  ::)

Looks great fairplay ;)

Thanks!

Nice work !!when is it going into production !!!LOL👍

Funny you should mention that . . .  ;)

Are we there yet ? ;D

You've been watching 'Wide Awake Club' too much - Timmy Mallet yelling, 'Are we nearly there yet . . .?'

Patience, child . . .  ;)

 ;D ;D

Ok, Clive; how is it progressing?

I'd nearly forgotten about that . . .

I got everything hooked up, checked, re-checked all the wiring and connections then switched on. Blew the on-board 2A fuse. Replaced the fuse and it did the same again. I only had those two 20mm 2A fuses so sent for more, meantime gutted a couple of larger 2A fuses and soldered the fusible wire across the dead 20mm one.

Still the same so I put the detector aside 'just for now' (allegedly until the new fuses arrived . . . ) Completely lost heart in it even after the new fuses came so haven't touched it since. Got a feeling it's something I've done wrong but need to be in the mood to even feel like trying to figure out what . . .

Bit difficult to fault-find it without a cct diagram - all I have is a connections diagram so dead in the water right now.

So thanks for asking but no good news yet I'm afraid! I'll just have to wait until my Muse decides to make a re-appearance . . .

"Nil desperandum" if you can build something that complex, I'm positive that you will sort it out,after all,step back from it,pat yourself on the back,and all of a sudden the solution will come to you, you have done so well mate !!
Looking forward to hearing that the project is completed and exceeds even your own expectations .👏👏👏👏👍

I was well impressed by your initial progress and recon you will soon resolve the present little problem. Perhaps the supplier can point you in the right direction? 

PS...........

                    I wonder if it could be an earthing problem and the power is going directly to earth, rather than into the circuit?

Thanks for the encouragement, guys.

I had wondered about a dead short myself - will have to have a good look at it when I get bored the opportunity.

I was doing a few tests to try and narrow the problem down until I ran out of fuses - first I disconnected the coil (still blew the fuse) and then I disconnected the pins from  socket 1 which supply the speaker and reset button. Still blowing the fuse at that point, which was when I ran out of fuses. At least I can discount those . . .

Got myself involved in something technical at the moment but when the bench is clear I'll have another look.

Just a thought, if you have access to a current limited power supply (common bench PSU) you could lash this in instead of the fuse and battery. Just set the power supply's current limit to 2A. This would allow you to continue fault finding without blowing more fuses or damaging anything, when you've got the fault sorted reconnect the battery/fuse.

 

I do have a bench power supply but it's not current-limited, only voltage-regulated.

I could build a current-limited one but I got out of that when I was into Amateur Radio - I was building test gear to test the test gear, IYSWIM. It's like a never-ending cycle.

But yes, that's a sensible approach.

What news from the construction front Clive?