Voodoo Main Discussion

[Qiaozhi]

hello everyone, this week I did several tests. I balanced the super d, no problem to do so, but the results on the display are not very good. I think the tuning is not yet set on my coil. (iron, non-ferrous). I also made a large size omega coil, in litz wire of 0.004 * 175 strand, damp @ 880r. it gets a delay at 10us. but then on the voodoo, it does not work at all ..... I do not understand!? I then connected a tesoro, the same as that of george's book. I have damper @ 1.5k, it works, but the voodoo is not stable at all .. I have not done the tesoro rx test ..

I would suggest concentrating on the Tesoro coil while you get the detector set up, as the default settings are good for that particular coil. Your damping resistor seems far too high to me. Check the PI preamp output on the scope and make sure that the coil is critically damped. Any under-damping may cause problems.
Also, get the PI mode working first before setting up hybrid mode.

[Qiaozhi]

I just did the test with rx tesoro spider, 15.4mh and 22nf, it works, but .. I think the settings I made are not good. George, can you tell me what value to put to validate average settings?

Look at page 31, Fig. 3-21. This shows the alignment of the DISC sample pulse with the output of the DISC preamp. Adjustment of the DISC sample time can be done from the menu system.

I also have problems in the pulse mode, it works, but the voodoo emits constant beeps beeps between each passage of the target on the coil ... this also occurs in hybrid mode

See post #467

another question, where should we connect the shield ground?

The shield ground connects to battery positive, which is 0V.

[lamoiz]

I would suggest concentrating on the Tesoro coil while you get the detector set up, as the default settings are good for that particular coil. Your damping resistor seems far too high to me. Check the PI preamp output on the scope and make sure that the coil is critically damped. Any under-damping may cause problems.
Also, get the PI mode working first before setting up hybrid mode.

Here are the measurements, I used my adjustment potentiometer. the measurement on tp3.


but even now, the detector emits a lot of beep beep beep between each passage of target ...

[Qiaozhi]

Here are the measurements, I used my adjustment potentiometer. the measurement on tp3.
[ATTACH]53811[/ATTACH][ATTACH]53812[/ATTACH]

but even now, the detector emits a lot of beep beep beep between each passage of target ...

I would have expected around 680R for the damping resistor, so that looks good.
The next thing to check is the main sample pulse alignment. See Fig. 3-19. If you try to sample too early, while the PI preamp output is still in saturation, the detector may become a bit jittery.

[lamoiz]

I would have expected around 680R for the damping resistor, so that looks good.
The next thing to check is the main sample pulse alignment. See Fig. 3-19. If you try to sample too early, while the PI preamp output is still in saturation, the detector may become a bit jittery.

fig 3-19 tp3 tp 11 what do you think?

[Math]

FBS coils for Explorers/Etracs ive measured..

Standard coils..
The 10" slimline (in between the early 10.5" and later 11" pro)
TX @ 580uH/0.9R RX @ 510uH/5.7R

The 11" Pro coil.. TX @ 577uH/0.8R RX @ 514uH/5.3R

Aftermarket coils..
Detech 8x6" SEF.. TX @ 578uH/0.8R RX @ 517uH/5.0R

All closely matched and the RXs in these mutual DD setups
have an Fres of around 300 to 400khz

The FBS square TX drive has a very fast switchoff - not
dissimilar to a PI and produces 3-400khz size peaks like 'spikes'
on the RX thats used alone for detection.. like a line of miners swinging their picks
at the silver and gold.. if you wish to these coils tune well
around 25 to 30khz (to match the main freq set of the TX drive.. the PPS if you like)
This 'high vlf freq' giving good sensitivity to small low conductors..

Used untuned on a PI these allow a sub 10us sample delay on the RX second peak
when using a good 150 or 200V mosfet on a fully resonant drive 5x less capacitance
and no need for the diode it just adds lumps n bumps when trying to keep a
smooth flyback at these levels.. i dont like to hear those magic hammers banging around inside my machines ive heard enough of those thro the stones and my bones over the years
Gains are in the lower noise and faster sampling.. matched for finding those pennies from Heaven and we must keep in harmony with Eric and remember why and for whom he invented such wonderful detectors.. sure they were better designed for finding big things deep like snettisham hoards round circles and such.. I think he knows more than hes let on about the energies at these places..
Perhaps we should pause just for a minute to wonder why he chose 86hz over 100? and I think ive remembered correctly her name is Kathleen

[MartyJ1963]

Thanks George, Regards, Marty.

[godigit1]

Here are the measurements, I used my adjustment potentiometer. the measurement on tp3.
[ATTACH]53811[/ATTACH][ATTACH]53812[/ATTACH]

but even now, the detector emits a lot of beep beep beep between each passage of target ...

Are you getting noise type beeps or multiple target response?
If multiple target response is the problem your coils may be phased reverse.
Had that problem first trying my last coil.
Best

[lamoiz]

Are you getting noise type beeps or multiple target response?
If multiple target response is the problem your coils may be phased reverse.
Had that problem first trying my last coil.
Best

hi Godigit, to calibrate the voodoo, I used a tesoro spider.
they are not inversion beeps, they are beeps, even if there is no target on the coil. This happens in pulse mode, and really almost not in hybrid mode. I have checked all the measuring points, everything is ok .. I do not understand where it comes from. ??
Another subject, I changed r66 by a 180r, this one has not cooked, but it is still very hot ...
With the tesoro coil, the detection distance is very small .. cola can about 30cm and gold ring 5 cm .. it is very little anyway ..
I will try it outside, just to confirm that it is not a problem related to the environment of my workshop

[lamoiz]

test carried out, outside ... device still beeps beeps beeps non stop

[Qiaozhi]

fig 3-19 tp3 tp 11 what do you think?
[ATTACH]53813[/ATTACH]

Fig. 3-19 shows TP10 and TP3 (not TP11).
What you're showing is the DISC preamp output versus the main sample pulse (and that doesn't look correct anyway).

Can you show the PI preamp output versus the main sample pulse?

[surfdetector]

Fig. 3-19 shows TP10 and TP3 (not TP11).
What you're showing is the DISC preamp output versus the main sample pulse (and that doesn't look correct anyway).

Can you show the PI preamp output versus the main sample pulse?

[Removed erroneous attachment]

Just for comparison purposes I have attached the PI pre-amp output versus the main sample pulse from my machine.

[lamoiz]

Fig. 3-19 shows TP10 and TP3 (not TP11).
What you're showing is the DISC preamp output versus the main sample pulse (and that doesn't look correct anyway).

Can you show the PI preamp output versus the main sample pulse?

indeed I had to put the wrong photo ..oupss and obviously, Surf also made a file error !!! well I'll take a photo tomorrow ..tp3 tp10.

[surfdetector]

TP10 versus TP3



This one might be better

[Qiaozhi]

[ATTACH]53824[/ATTACH]

This one might be better

That looks good.
I've removed your erroneous attachment in post #478. I guess you didn't really want anyone seeing that.