TESORO GOLDEN SABRE

[simonbaker]

On my TGSL I accidentally weld the GND and -6, 25V. Now detector works, but with reduced sensitivity. Voltages are okay -6.25 V and 7.99 V, what should I check first? I have no oscilloscope.

Please give a complete description of your project; what schematic; what pcb; photos of your PCB (both sides) and your coil; how you built coil; coil parameters (size, resistances, inductances); how you nulled the coil; any parts substitutions?

What air distance can you detect at? What do you use for target (1 Euro coin is best)?

A video with sound of your air tests with 1 euro coin might be helpful.

Regards,

-SB

[0cool]

Please help

On my TGSL I accidentally weld the GND and -6, 25V. Now detector works, but with reduced sensitivity. Voltages are okay -6.25 V and 7.99 V, what should I check first? I have no oscilloscope.

[mikebg]

DRYING with MICROVAWES

This is due to moisture differential. Apply a couple of coats of polyurethane, or fiberglass resin or (as Mike suggests) epoxy. Make sure whatever you put on it can withstand the heat.

- Carl

There is an ideal instrument to remove moisture from the wood and warming the wooden formers before you put on epoxy resin. This is the microwave oven. For better results do not put oven at full power. Warming thus wood greedily absorbed the epoxy resin. We have not tried to put coated with epoxy wood again in the microwave with the purpose of the resin to solidify rapidly, but microwave heating of ferrite cores is used for quick stick with epoxy of coils and transformers. Perhaps heating of such devices with ferrite cores in a microwave oven is the only method of ripping off successful and use their components again.

[Carl-NC]

Some formers.. I need to start making them out of a plywood as pine tends to warp when heat is applied to one side. Also, they tend to crack easily.

This is due to moisture differential. Apply a couple of coats of polyurethane, or fiberglass resin or (as Mike suggests) epoxy. Make sure whatever you put on it can withstand the heat.

- Carl

[Mullihaka]

Phase shift vs residual voltage?

I have a request for all members who have a TGSL which has detection distance of 30cm or more for a (1 eur) coin in the air.

Would you be so kind and measure:
- the phase shift between TX signal and RX signal (at pin 7 of the LF353)
- residual voltage at the preamp output (pin 7 of LF353)

I'm trying to figure out what kind of combination of the abovementioned I should try on my TGSL to get it beyond 20cm.

I can get the phase shift of 20 degrees or residual voltage of 450mV, but only one at time. Having either of them "as it should", the other jumps far away.

All results appreciated,

Andy

[sajkel]

http://analog.chipfind.ru/search.htm?s=LM308 Who tasted

[dfbowers]

Thanks for the advice on making formers. I will try covering them with resin first to see if I can prevent warping. I will put together my process making coils and post in the "mechanical" section near the bottom of the forum.. I think that it would be more appropriate to post the whole thing there.

[mikebg]

Some formers.. I need to start making them out of a plywood as pine tends to warp when heat is applied to one side. Also, they tend to crack easily.

Don

Don, it is wery dificult to make formes of plywood. Better impregnate wooden formers with epoxy resin, but you should warm the wood about 100 deg. C in advance to absorb the resin.
Mike-BG

[simonbaker]

Some formers.. I need to start making them out of a plywood as pine tends to warp when heat is applied to one side. Also, they tend to crack easily.

Don

I would be interested in seeing the whole process of making the coil housing that you use, maybe in a separate thread. The wooden forms look like they were crafted with much care.

Regards,

-SB

[galaksi]

dfbowers;

technical dimensions, please

[dfbowers]

Some formers.. I need to start making them out of a plywood as pine tends to warp when heat is applied to one side. Also, they tend to crack easily.

Don

[ik5pwr]

good job ,nice work , do you have a pattern of wood model ?

regards Alex

[dfbowers]

Bottom view of homebuilt TGSL coils:

[dfbowers]

TGSL and smaller coils

Well now that It's a little warmer out and I finally got a chance to do a little detecting with the TGSL, I have been comparing the performance of different coil sizes. The advantages of an 18cm coil over a 27cm coil are becoming more apparent. These advantages are not obvious when just doing bench testing:

1. 18cm coil is lighter, and even though a 27cm coil covers more ground,
the fact that you can swing a smaller coil a little faster makes up for it.

2. 18cm coil is easier to pinpoint with, which makes digging faster and can
make you more productive.

3. 18cm coil is less noisy when in actual use.

4. While a 27cm coil can give you more depth, it's advantage is not that
apparent when used in the ground. It "sees" less ground in relation to
targets.

5. 18cm coil is cheaper and easier to make.

6. 18cm coil has better target separation in trashy areas.

7. 18cm coil is easier to use around objects.

8. 18cm coil is much more "sturdy".

Try biuilding one.. you might like it!

[simonbaker]

I literally bought over a mile of .25mm wire off of ebay for 50 bucks! That should hold me for a lifetime.. I aim to make more coils!!

Sounds familiar - I have an 8 lb spool... except I got heavier gauge stuff thinking higher Q would be better, but I think not now, at least for RX coil with standard TGSL circuit -- lower Q actually may be better for various reasons. So at least I can repair vacuum cleaners and starter motors...

-SB