TESORO GOLDEN SABRE

[simonbaker]

Compadre mod for TGS?

I noticed in Compadre thread that a mod is to drive TX oscillation directly from battery voltage instead of regulated supply to get higher voltage, more depth.

Anyone try that for TGS?

[Max]

I noticed in Compadre thread that a mod is to drive TX oscillation directly from battery voltage instead of regulated supply to get higher voltage, more depth.

Anyone try that for TGS?

Hi,
you could do that... but maybe is better changing also the zener there too...

In any case it's not so good cause there are little fluctuations on battery rail... and it's unregulated voltage.

I think will be good on e.g. power supply / bench... but could be a big mess on batteries.

Kind regards,
Max

[simonbaker]

Hi,
you could do that... but maybe is better changing also the zener there too...

In any case it's not so good cause there are little fluctuations on battery rail... and it's unregulated voltage.

I think will be good on e.g. power supply / bench... but could be a big mess on batteries.

Kind regards,
Max

I notice that the negative rail is unregulated anyway.

Can you tell what the nature of the fluctuations on the battery rail is? Does it have a frequency signature?

[Max]

I notice that the negative rail is unregulated anyway.

Can you tell what the nature of the fluctuations on the battery rail is? Does it have a frequency signature?

Hi,I mean it's floating voltage... the battery drop is an issue (some battery less than other kind... e.g. nimh have about flat voltage till they drop very sharp, so big fluctuations are at initial and final drops, other batteries have much larger swing during discharge, e.g. old zinc-carbon)The fluctuations are also related to audio stage: when using internal speaker yor battery voltage have a ripple cause of current drained in that process: you can place a tank capacitor there to compensate more but it's always an issue... with headphones the problem is much reduced. Frequency is the audio frequency...some hundred Hz.It's right you have unregulated negative rail, but this affect just op amps: the tx stage uses +8v regulated there....only. If you change for battery rail... your tx supply voltage will follow the drop rate of battery: means huge instability at fast drops.Kind regards,Max

[Unregistered]

Max on new (30cm) TGS coil you got around 15,90khz?

[Max]

Max on new (30cm) TGS coil you got around 15,90khz?

Hi,
did you tight the wire with tape or something ?

You must get 14.6-14.7 Khz on tight wire.

Kind regards,
Max

[Unregistered]

Mr.Max i only thinking about that.
You wrote your tx colil is around 5,7mH when i calculate with paralel 20n capacitor
result is 15,91khz.Im litle confuse..

Regards!
Thanks for your time.

[Max]

Mr.Max i only thinking about that.
You wrote your tx colil is around 5,7mH when i calculate with paralel 20n capacitor
result is 15,91khz.Im litle confuse..

Regards!
Thanks for your time.

Hi,
it's colpitts oscillator: capacitance at oscillator tank is by the 2 capacitors there... about 21.8nF not 20nF

This will give you calculated value of about 14.3Khz, but you know any meter has tolerance... so probably it's less than 5.7mH ... and capacitors could give (on mine PCB) something less than 21.8nF.

I can only say that you'll stay around 14.5Khz and few hundreds Hz variations are due to tolerances at coil and capacitors.

If you e.g. tighten not enough the wire at coils you'll get higher frequency than tightening very strong it... that's about coils... you'll difficault made 2 exactly the same using simple copper wires boundles... even with lot of care.

Now, I've used good quality components and lot of care at coil... so it's about accurate with say +-200Hz respect to indicated value when you try to replicate, cause of the above tolerances. Not big deal... select capacitors or add / subtract a few turns to get exact frequency if needed (usually isn't).

Kind regards,
Max

[simonbaker]

Hi,I mean it's floating voltage... the battery drop is an issue (some battery less than other kind... e.g. nimh have about flat voltage till they drop very sharp, so big fluctuations are at initial and final drops, other batteries have much larger swing during discharge, e.g. old zinc-carbon)The fluctuations are also related to audio stage: when using internal speaker yor battery voltage have a ripple cause of current drained in that process: you can place a tank capacitor there to compensate more but it's always an issue... with headphones the problem is much reduced. Frequency is the audio frequency...some hundred Hz.It's right you have unregulated negative rail, but this affect just op amps: the tx stage uses +8v regulated there....only. If you change for battery rail... your tx supply voltage will follow the drop rate of battery: means huge instability at fast drops.Kind regards,Max

Ok, thanks.

I plan to experiment with 7 rechargeables = 7 * 1.2 = 8.4 volts, no regulation at all (leave out LM7808 ), just big capacitors and see how it works and any problems. I'm thinking original design was for alkaline and regulation was mainly for providing more hours of use as battery voltage dropped slowly from 12 v to about 10 v. As you say, rechargeables have flat discharge curve, maybe regulation no so important? I'll try it after build working MD, just slowly testing and building first.

[Aziz]

Hi Simon,

Ok, thanks.

I plan to experiment with 7 rechargeables = 7 * 1.2 = 8.4 volts, no regulation at all (leave out LM7808 ), just big capacitors and see how it works and any problems. I'm thinking original design was for alkaline and regulation was mainly for providing more hours of use as battery voltage dropped slowly from 12 v to about 10 v. As you say, rechargeables have flat discharge curve, maybe regulation no so important? I'll try it after build working MD, just slowly testing and building first.

I am interested on your results. Post it here as soon as you have some.

But I am very sceptical. It will cause slightly drifting due to charge decrement. The voltage of the cells will go down, even the amount is not much. This could cause much drifting problem.
Aziz

[simonbaker]

Hi Simon,



I am interested on your results. Post it here as soon as you have some.

But I am very sceptical. It will cause slightly drifting due to charge decrement. The voltage of the cells will go down, even the amount is not much. This could cause much drifting problem.
Aziz

I'm sure you're right, but I'll test sometime. What do you think will drift? Even if frequency drifts a little, would the phase relationships change that much? In fact, we all have different frequencies due to differences in parts, coils etc. If drift very slow, motion-mode detector should not be bothered. But I am not expert.
-----------
I like the 9.6 v rechargeable battery pack for RC cars, etc. I plan to try using that with LM2941 low dropout regulator (instead of LM7808 ) with TGSL also as experiment. It seems like a waste to use 12 v to get 8v. LM2941 should make alkalines run longer also. I got sample of LM2941, don't know where to buy yet.

Regards,

-SB

[driscoll]

Hi Max,
Hi Ivconic,

I read your articles and I must say that it is impressive. Golden Sabre would be more efficient than the bandido ?

[Max]

Hi Max,
Hi Ivconic,

I read your articles and I must say that it is impressive. Golden Sabre would be more efficient than the bandido ?

Hi,
if we talk about standard, factory made, detectors... I think bandidoII is better than TGS, even if difference must be small on same coils.
BandidoII is newer than TGS... have better components by default.
Also have manual GEB and all-metal no-motion... TGS haven't in factory made : just GEB preset and motion mode.

If we talk, instead, of homemade clones... well... it's really difficault provide an answer: a properly made bandidoII tuned for max sens with an homemade coil it's a big beast... like homemade TGS with big DD coil.

Which clone is best ?

Much depends on fine tuning and coils: with extremely good tuning the bandidoII circuit is better than TGS circuit, no dubt. That's also cause bandidoII use by default lower noise components... but if you replace all them in TGS too you'll not notice such good performances.
The notch section of TGS is a source of noise... most of the time: in TGSL this is avoided cause you haven't notch, but I tryed with same bandidoII components and didn't get same good results.

Unfortunately, if you simply replicate bandidoII and use a standard coil you'll end up with a good detector but not as good as TGS with big custom coil is.
Also... I made a DD22cm that's really better of CC 9x8'' that, in theory, must be very good about depth. Inconsistency at coil manifacturing I think... some few you can buy are very good...but the majority are average coils. Or simply small mismatch with TX oscillator or RX preamp cap ???

So you need always custom, homemade coils for max performances.

BandidoII works really good on DD coils, any size...to 30cm I tested and pinpointing is very nice using no-motion feature, also on large coils. You can mod TGS for that feature too, of course, or use external pinpointer for elusive stuff.

The big advantage of TGS is that there are plenty of informations, details and data you can use for construction... where bandidoII lack many useful informations.

Another problem with bandidoII is that, it's generally more sensitive to steel stuff than TGS... so disc is very critical also, and works good when you set at around 4... in TGS your iron/steel disc is very good starting at 0... usually you use 2 as setting just to eliminate small foil stuff, iron is already all rejected... steel get only on e.g. large nails.

So, the answer isn't, cannot be definitve... and depends much on DIY abilities.

In my case resulted that bandidoII has little more sens than TGS... but this changing many things at circuit and components: it's not bandido anymore! On standard schematic/components I get about same detection as with TGS w/ same coil.

Kind regards,
Max

[eclipse]

For the things Max says ( about old types of the components in TGS)
I ordered 3 weeks ago components worth $180 (and damn im still waiting for them) just to push up as much as I can the electronics. The components include all (except pf caps) Wima - series FKP2 and MKP2 and electrolytics caps: Nichicon muse fx. All resistors are ultra low noise 10uV CMF55 series. Transistors are standard onces: BF245, PN2222/PN2907 (plastic ones). The IC: LT1057 in the front stage, two LT1018 comparators, LT1008 insted the 308, and 2xOPA2277.
The board, I decided to use Ivconic's, but i had to change almost all capacitors with other bigger footprints for the Wima's. Also the box I ordered is large, 160x100 i can add some stuff.
The layer with the traces I decided to add ground plane, some of the jumpers will be gone cos of that and also will order for manifacturing, its about 30$ so not that high.
As soon as I am done with all that will post the results, hope I am not throwing money on the wind ...

[driscoll]

Thank you Max for this answer very explicit.

Bests regards