TGSL Tuning & troubleshooting

[dfbowers]

I ended up testing and adjustment and stuck a box of super glue.

I wish everyone luck in their work.

Excellent! I like to see some consistency between our projects. I like your "in ground" results..

Which mods have you implemented?

Don

[Vladimir]

Excellent! I like to see some consistency between our projects. I like your "in ground" results..

Which mods have you implemented?

Don

Thanks, I hope that we will find more useful modification.
See my previous posts that explain my modification and especially post #188.
Greeting

[Vladimir]

The final design .....

[dfbowers]

The final design .....

Nice.. Are you using an external GB adjustment?

What type of cable are you using between the coil and control box?

Don

[Vladimir]

Nice.. Are you using an external GB adjustment?

What type of cable are you using between the coil and control box?

Don

Thanks
Yes, I used an external GEB control in the range of 10k (potentiometer) + 76K fixed resistor.
The cable is 2 x wire + shield in silicon isolation.
The batteries are 12 x 1.2V NiMH 900mAh.

[simonbaker]

Birthday

It's late and I don't have proper time to gush, but...

"Christmas came early" here with arrivals from dfbowers and Stefano.

Courtesy of dfbowers, complete TGSL machine. I'm bowled over. Can't handle it. I'm afraid to touch, I just stare... it would have been like parting with first-born for me... I will need time to absorb it all, pull myself together, and prepare for a test drive. Do I need a license? Helmet? Goggles? Scarf? More to come...

Stefano, sparring with the U.S. Postal Service, managed to finally circumvent every obstacle they threw at him and deliver to my doorstep a bona fide, true blue, real McCoy, honest to gosh, that ain't hay, genuine, dyed in the wool... EURO. And a couple of other coins I've never seen before. 1 Euro -- the missing link. I'm liberated...

The spirit of generosity and teamwork makes me weak in the knees.

I'm also sweating bullets because the heat's on; these are really valuable tools. Now I have to get busy testing, analyzing, experimenting, tuning, and troubleshooting -- when life doesn't interfere.

Anyway, thanks guys, I very much appreciate the effort and outright cost to get me these items. I'll do my best to put them to good use and hopefully generate some info that might be useful to others trying to troubleshoot and tune up their TGSL.

Still catching up with much crap after being away, so make take time.

lunamay -- what's going on? Did Ivconic hire you? Ok, I once got wild beeping when I put a LM393 in backwards and fried it. Put in good chips. Replace the LM7808 for good measure. Wire up a battery connector that is fool-proof. Then measure the V+, V- for us. Put frequency counter on TX coil, what is the frequency?

Having fun anyway.

Regards,

-SB

[simonbaker]

Thanks
Yes, I used an external GEB control in the range of 10k (potentiometer) + 76K fixed resistor.
The cable is 2 x wire + shield in silicon isolation.
The batteries are 12 x 1.2V NiMH 900mAh.

Can you provide a diagram of your cable showing exactly the wires, shields, and connections?

Regards,

-SB

[simonbaker]

dfbowers TGSL

Just did a quick turn-on of dfbowers TGSL, some initial observations.

1. Of course I didn't know I was using bad headphones, so had to open up his box and do a little scoping...

I notice he uses two 9 volt batteries for supply and has a neat way of connecting them with one 9v battery clip -- I'll get some photos later.

(it's fun having my hands on a beautiful finished machine. I encourage dfbowers to do a thread detailing his construction technique, parts, machining, etc. The pole is very nice with pins that lock the sections together. You've seen picture of coil -- I'd like to know how he made the two "flanges" that grasp the pole end. He uses metal washers at pole/coil pivot, so apparently not a problem to put a little metal there. I'd like to know how he fills ("pots") the coil in the form -- epoxy? How keep it nulled? USB cable works nicely.)

2. I think I figured out which pot is which and the switch positions, just by playing and testing. Didn't confirm by following wires yet.

3. He chose to use headphones-only, no speaker.

4. I tried a very quick "air test" in my "lab/workbench (ha ha ha...)". I think I learned something valuable. My workbench is #@($|^& noisy! I could not get good air depth with any coins at a low chatter sensitivity. Maybe 10 cm at best. So I took dbbowers TGSL to another room. With coil resting sideways, I could turn sensitivity higher, and air depth was much better, probably 20 to 30 cm. I didn't do exact measurement because I'm sure there is noise in every room. This helps confirm my feeling that you'll never measure good air depth until you get away from noise sources. I believe noise can actually block a small target signal by breaking it into pieces. The small pieces cannot get through the following low pass filter. So instead of getting a noisy beep, you just get no beep at all. This may be a primary reason many of us think we have poor depth. We must get away from noise sources to do test. Now with dfbowers MD, I can evaluate whether I am away from noise sources -- very handy.

5. Discrimination test of a US Nickel seemed to show nickel is knocked out near the end of the discrim pot setting. With my circuits I usually find it closer to the middle I think. But I'll retry that test in less noisy area.

Of course we'll never know if anything shifted during shipping, etc. But I'll continue tests and comparisons and get better data as time goes on.

Q - a question for dfbowers -- does this MD you sent have the "dfbowers sensitivity mod", or is it the original circuit?

Regards,

-SB

[dfbowers]

Just did a quick turn-on of dfbowers TGSL, some initial observations.

1. Of course I didn't know I was using bad headphones, so had to open up his box and do a little scoping...

I notice he uses two 9 volt batteries for supply and has a neat way of connecting them with one 9v battery clip -- I'll get some photos later.

(it's fun having my hands on a beautiful finished machine. I encourage dfbowers to do a thread detailing his construction technique, parts, machining, etc. The pole is very nice with pins that lock the sections together. You've seen picture of coil -- I'd like to know how he made the two "flanges" that grasp the pole end. He uses metal washers at pole/coil pivot, so apparently not a problem to put a little metal there. I'd like to know how he fills ("pots") the coil in the form -- epoxy? How keep it nulled? USB cable works nicely.)

2. I think I figured out which pot is which and the switch positions, just by playing and testing. Didn't confirm by following wires yet.

3. He chose to use headphones-only, no speaker.

4. I tried a very quick "air test" in my "lab/workbench (ha ha ha...)". I think I learned something valuable. My workbench is #@($|^& noisy! I could not get good air depth with any coins at a low chatter sensitivity. Maybe 10 cm at best. So I took dbbowers TGSL to another room. With coil resting sideways, I could turn sensitivity higher, and air depth was much better, probably 20 to 30 cm. I didn't do exact measurement because I'm sure there is noise in every room. This helps confirm my feeling that you'll never measure good air depth until you get away from noise sources. I believe noise can actually block a small target signal by breaking it into pieces. The small pieces cannot get through the following low pass filter. So instead of getting a noisy beep, you just get no beep at all. This may be a primary reason many of us think we have poor depth. We must get away from noise sources to do test. Now with dfbowers MD, I can evaluate whether I am away from noise sources -- very handy.

5. Discrimination test of a US Nickel seemed to show nickel is knocked out near the end of the discrim pot setting. With my circuits I usually find it closer to the middle I think. But I'll retry that test in less noisy area.

Of course we'll never know if anything shifted during shipping, etc. But I'll continue tests and comparisons and get better data as time goes on.

Q - a question for dfbowers -- does this MD you sent have the "dfbowers sensitivity mod", or is it the original circuit?

Regards,

-SB

Simon

Yes, the detector has the sensitivity Mod. I suspect that noise will play a major part of performance observations, and you may find that there is not that much wrong with your circuit. But now you have something a little more portable to deal with. I can get really good results away from my house, and I live in a fairly rural area. Sometimes good inside depending on how many TVs computers and motors are running.

I typically set the disc at a minimum and it still knocks out most iron. Set the sensitivity around 12:00 and you should still pick up a euro at 30cm. In my house, it's dead quiet at that setting so that should give a baseline on noise levels.

Don

[Dennis the Mennis]

4. I tried a very quick "air test" in my "lab/workbench (ha ha ha...)". I think I learned something valuable. My workbench is #@($|^& noisy! I could not get good air depth with any coins at a low chatter sensitivity. Maybe 10 cm at best. Regards,

-SB

Hi -SB ,

I think we all understand your noise problem now .....



regards ,

Dennis the Mennis

ps I didn't see dfbowers MD in your workshop ...

[dfbowers]

Hi -SB ,

I think we all understand your noise problem now .....



regards ,

Dennis the Mennis

ps I didn't see dfbowers MD in your workshop ...

This is the way that it's SUPPOSED to work. same unit lock, stock and barrel (Ok, control box, pole and coil). And that was before the mod!

http://www.youtube.com/watch?v=fwU0iweAimA

[simonbaker]

Hi -SB ,

I think we all understand your noise problem now .....



regards ,

Dennis the Mennis

ps I didn't see dfbowers MD in your workshop ...

Ha ha! Yes, that looks like my room when I clean it up.

dbbowers MD was there but excused itself and booked into the Hilton - I don't know why...

(nice rug though, eh?)

[simonbaker]

This is the way that it's SUPPOSED to work. same unit lock, stock and barrel (Ok, control box, pole and coil). And that was before the mod!

http://www.youtube.com/watch?v=fwU0iweAimA

And with metal objects nearby even...

So I will work to replicate that, then it will be my benchmark for tests.

I'm stoked!

-SB

[Vladimir]

Can you provide a diagram of your cable showing exactly the wires, shields, and connections?

Regards,

-SB

I hope it's a good explanation?

[simonbaker]

I hope it's a good explanation?

I think I understand. It looks like audio cables with RCA connectors. Each pair of wires is one shield and one inner wire.

The reason I ask is that I have used the same cable types sometimes.

But I think maybe there is a problem with these, depending on how much noise is around.

Here is why:

I think the TX cable is OK. It is the RX cable that may be the problem.

The reason is that because the LF353 is a differential amp, it should ignore common mode noise signals.

But if we use a pair of wires where one is the shield, then I think noise affects the wires differently, because the outer wire shields the inner one. So maybe the differential amp picks up the noise differential.

It seems like a twisted pair inside a separate shield might be better. Any noise that gets through the shield should affect both wires equally, and then be ignored by the diff amp.

However this is complicated by the fact that one of the RX wires is grounded at the coil shield. In that case, maybe the audio cables are best after all?

I'm really am not sure what is best. You seem to get good results with audio cables, but you also made mods to reduce noise.

I find the cable wiring difficult to understand, especially the grounding of the RX coil in the shield. I wonder if differences in cabling is causing some TGSLs to be more sensitive to touch or feedback beeping. I think there needs to be some testing of this, and check what cables we use.

-SB