Inside the TX-2002 pinpointer

[sinclairuser]

I can't see that a strip down would reveal much, but perhaps measuring the coil values might be useful, as well as the parts you think might be popluted on his unit.
Thanks,
Martin
PS. I intend to see if I can melt the glue around the OEM coil in boiling water and see if I can slip it out, but that will be middle of next week.

i was only thinking about the coil measurements and the unknown components, this is someone else's pinpointer after all, totally striping it would not be good practice anyway.
but in curcumstances like yours all info is helpfull.

[mr.sneezy]

I'm back from some time away.
The thread's quieter than I thought it would be after all the required info was posted up.

Who's good at creating the schematics on the forum ?

Cheers,
Martin

[walkman]

you do not want DVD because DVD you got. you want Inside The Metal Detector scanned, which is copyrighted. ask George and if he will agree to send you
files I will do. if not so that is not.

: Nono:: Nono:
as you say, I wonder?

[sinclairuser]

since this thread is active again, specs of tx 2002 belonging to my customer:- 42 ohms, 3.02mh,33nf.
works out at 15942.6hz res, and 2213.41hz operating freq.
if i understand this calculator correctly, the missing components are missing on this too, i suspect that if you tested 10 of these you would get ten different coil specs, my guess is they just bung in anything.

[kt315]

: Nono:: Nono:
as you say, I wonder?

why I must scan you INSIDE THE METAL DETECTOR? may be I must give you my wife, my car, my house too?

[mr.sneezy]

@sinclairuser
42 ohms on the coil is huge is it not ?

I suspect you're right that they stick any old ferrite coil into these and hope for the best. I bet some are surplus FM radio tuning coils or similar.

I'm about to attempt to remove the ferrite from the pointer tube. Hopefully without too much swearing

[sinclairuser]

that would be my guess, i'm not prepared to accept that these are hand tuned individually, i checked this 3 times with different equipment, but they all read the same within the meters specs.

[Qiaozhi]

: Nono:: Nono:
as you say, I wonder?

Inside the METAL DETECTOR is copyrighted, so KT315 is correct in not sending you a scanned image.

If you wish to obtain a copy of ITMD, then please go here and order one ->
Inside the METAL DETECTOR - Published September 2012

[Davor]

Well, that also depends. Fair use (act) allows copying a part of a copyrighted material for non-commercial purposes. Educational, e.g. DIY purposes are well within the bounds. So in fact it would be OK if a schematic is posted - for educational purposes.
Copying a whole book would be problematic, of course, but copying a chapter for educational purposes is something else.

Personally I like my copy of ITMD very much, and I don't intend to provide any copies of any parts as long as the book is in circulation, and the very authors are here on this forum, and willing to help.

[Qiaozhi]

Copying a whole book would be problematic, of course, but copying a chapter for educational purposes is something else.

If it's for your own education, then that's ok. But copying a chapter to send to someone else is not ok.

Glad you like the book!

[mr.sneezy]

The OEM coil

I've done a bit of playing about with the TX-2002 this weekend (another very hot one here).
I removed the original ferrite coil from the pointer. It turns out that the coil was glued in with hot-melt, and putting the pointer in freshly boiled water for a minute or so loosened it up a bit. Pulling on the two wires slowly got it out, well sort of. Half came out, half stayed in To get the second stuck bit out I drilled a 3mm hole in the pointers tip and pushed it out with a stiff wire (heated it again in boiling water first).

So it is the end of that coil as I suspected it might be. The ferrite was broken just below the middle. I'm not sure when this might have been broken, when new, when I tried bumping the coil free, when I levered on it with a screwdriver, when aliens broke into my shed and tampered with it, I dunno.
One small bit of news though is that it was approximately 160 turns of wire on a 100mm ferrite.


Since then I've reloaded the components back on to the TX-2002 PCB (with all new resistors and diodes), and then tested it by rewinding the 62 turns of 0.5mm wire coil onto the OEM ferrite (the longer broken piece of it).
With the OEM ferrite it's not as sensitive as my first ferrite (the 180mm long one) perhaps about 60% as good. The OEM ferrite might be inferior or too short now. I need to buy some more 0.5mm wire to continue as the bit I have has been used too many times. I noticed on the CRO display that the new coil generates a higher frequency than the old test coil, and the coil voltage is only 4V P-P, so I'm going to measure the L value next week before making another coil/coils for testing.

Also need to rat out a vibrator from an old phone and fit the components for that option.
Martin

[sinclairuser]

hi sneezy, before i got a whites bullseye pinpointer, i built my own out of one of those velleman kits, the coil for that was a ferrite and it was crap, so i experimented with winding coils, my favourite was not wound on a ferrite but a pole winder, like this,.
dont know if you get them down there or not, your supposed to wind your float rigs on them for fishing, anyway it was just the right size to fit into 15mm pvc pipe, and was wound like an elongated normal coil longways it was very directional which for a pointer i found desireable, i made two like that one without and one with ferrite glued inside and the wire wound around it, obviously the ferrite takes less windings but the ferrite less one wound with 0.5mm mag wire simply worked best.

[mr.sneezy]

Last bits

Two more (last ?) images of the improvement project.
The unit is actually now a useful tool. I tried it out in the garden and found all sorts of childrens toys (like Matchbox cars) buried under the top inch or two. Also found small items clothes peg springs no problem. So it seems to be ready to try out on a beach or country ruin now.

On my table top $1 coin test with the final coil I get 60mm face-on and 40mm edge-on (to the probe tip). This is a massive improvement from the useless detection 'range' out of the box. I'm happy with that for now, and the unit is worth the $30 I paid for it (LOL, 10 hours of tuning later).

The final winding for anyone else interested is a 100mm ferrite with 60 turns of 0.5mm diameter wire, wound 8mm from the end. The main board circuit is unchanged from original.

My last bit of tinkering was to fit a Haptic device and load the driving components. I used a vibrator from an old Huawei mobile phone. The vibrator in that one is flat round device that looks like a coin cell but isn't.
I used a BC549 transistor (fitted backwards to the silkscreen outline), a 1k drive resistor (R18 ) and a 10k pull down (R19) and a 1N4148 across the motor (D10). There is also a load resistor (R20) to drop the 9V down to about 3V across the haptic (or it might burn out). I found 62 ohms worked for my device. The setup works quite well.

[sinclairuser]

well done mate, i bet those missing components were more or less what you have added, its the only thing that makes sense there.
i see the coil didn't need to be as wound or as complex as it was, i think its obvious that they use pre wound radio ferrites, and just bung anything in probably the cheapest option, well some on here have been looking for a pinpointer project, and now this is as good as any if converted to surface mount it could be even better, but this will probably be igrored in favour of trying to "reinvent the wheel", at least thats what usually happens round here.

[miliciano]

Thank you mr.sneezy , I have one of this TX2002 (a GT2002) to test your mod.
I used 0,60 mm wire on 10x100mm ferrite and get best results with 60 turns 45.5 khz: face coin 45mm side coin 25-30mm.

Now it is a bit more usefull , will test today on field.