Voodoo Main Discussion

[MartyJ1963]

Hi Godigit,,,Really amazed at the results of your experiment. I for one will defnitely be having a go at it amongst the other coil variations I have already made templates for. I have all the materals/components to begin but I'm having to do it all in between some major repairs to the house that need fixing before Winter arrives. I should hopefully be starting soon though. Thanks again for all the details you posted. Regards, Marty.

[Qiaozhi]

Hi George,,,Can you recommend a brand/Model of 24v adapter for the battery charger pcb and what amperage please? I have 2 x 24v adapters here. One is 24v @1500ma,,and the other is 24v @208ma. I also have a 23v adapter @400ma but I suppose that would be too low wouldn't it? Thanks, Regards, Marty.

The input to the charger is 24V AC, and is expected to come from a mains transformer. As suggested on page 90, you could use a fairly standard mains transformer with two 0-12V outputs in series. The charger should also work with 24V AC from a power adapter with sufficient current capability.

[Qiaozhi]

Now the Rx coil needs damped to a pre value. the final damp will be at final assemble with a damping resistor set up.
Here is the Rx coil damped alone.

There is no requirement to damp the RX coil for Voodoo. It just needs to be induction balanced to the TX coil.

[MartyJ1963]

Thanks George. The only 24v AC charger I have only outputs 208ma but that wouldn't be enough would it? Thanks, Marty.

[Math]

Hi Qiaozhi my copy of Voodoo Project arrived today, I think its great
Is the TX pps set at 1khz and is it possible to add adjustment to the menu?
Thanks

[Qiaozhi]

Thanks George. The only 24v AC charger I have only outputs 208ma but that wouldn't be enough would it? Thanks, Marty.

Actually, if you connect the 24V DC adapter to the circuit it should still work. It won't even matter which way round you make the connections.

[Qiaozhi]

Hi Qiaozhi my copy of Voodoo Project arrived today, I think its great
Is the TX pps set at 1khz and is it possible to add adjustment to the menu?
Thanks

Yes, that would be possible, but at the moment I'm waiting for someone to replicate the project before there are any discussions about modifications.

[MartyJ1963]

Thanks George,,,but what I wanted to know is would 208ma be enough to charge a battery pack or would I need one with more current output? I'm wanting to put a battery pack beneath the armcuff on my detector shaft and not in the same enclosure as the pcb,,so I can swap out battery packs in the field. Thanks, Marty.

[Math]

Ok thanks Qiaozhi i will get cracking!
Performances will vary largely depending on the coil used/built?
I use Explorer/Etrac FBS coils on my modified Minipulse..
I think the lower inductances, higher Fres/faster Rx makes them ideally suited for PI iron disc
Early used 10.5" and later 11" pro coils (with bust lugs) are plentiful and cheap
they can be had for 50GBP or less as can the smaller coils.. the 8" and Detechs 8x6 SEF which is a very good coil
I know these are all DD/~OO but i find the narrower detection zone better for target seperation..
Im not sure if this will apply to the Voodoo design being based mainly around concentric type coils?

[Math]

George do you know anything of Eric Fosters PI discriminators.. the PPD1's?
After the C400 Deepscan they were early 80s i think and also housed in Arado 120 type enclosures with a similar centre zero meter for ferrous/non ferrous discrimination, auto silver foil rejection on sample delay? and ring pulls from gold rings by tone at low power settings. Apparently the meters worked well on the beach but could sometimes read non ferrous as ferrous on land
They had plastic oversize pipe stems that contained 8x D batts in the top section drawing only around 170mA ..good for the time! and very nicely handbuilt.
They used Garretts deepseeker type 8" co axial coil housings that contained tri planar concentrics I think
Inside the box there are 2 boards like Fisher 1265's ..power and PI circuitry on the bottom board with disc on top and the components are wonderful colours!
I have one named Eileen.. hand written on the board I assume by Eric.. I did get it running again its ~85pps same as the later Minipulses and with a large pulse width I remember around 250us
Its half reverse engineered and when Ive finished I plan to put the design up here..
TX circuitry I think is standard PI design and I will post up the coil values and Fres when i find my notes

[lamoiz]

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 ..

[lamoiz]

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?
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
another question, where should we connect the shield ground?

[Qiaozhi]

Thanks George,,,but what I wanted to know is would 208ma be enough to charge a battery pack or would I need one with more current output? I'm wanting to put a battery pack beneath the armcuff on my detector shaft and not in the same enclosure as the pcb,,so I can swap out battery packs in the field. Thanks, Marty.

You can see on page 90 that the 208mA is insufficient for the charger circuit shown in Appendix B, but you can alter that by changing the value of R1 according to the equations provided.

[Qiaozhi]

Ok thanks Qiaozhi i will get cracking!
Performances will vary largely depending on the coil used/built?
I use Explorer/Etrac FBS coils on my modified Minipulse..
I think the lower inductances, higher Fres/faster Rx makes them ideally suited for PI iron disc
Early used 10.5" and later 11" pro coils (with bust lugs) are plentiful and cheap
they can be had for 50GBP or less as can the smaller coils.. the 8" and Detechs 8x6 SEF which is a very good coil
I know these are all DD/~OO but i find the narrower detection zone better for target seperation..
Im not sure if this will apply to the Voodoo design being based mainly around concentric type coils?

What are the inductance values of these coils?

[Qiaozhi]

George do you know anything of Eric Fosters PI discriminators.. the PPD1's?
After the C400 Deepscan they were early 80s i think and also housed in Arado 120 type enclosures with a similar centre zero meter for ferrous/non ferrous discrimination, auto silver foil rejection on sample delay? and ring pulls from gold rings by tone at low power settings. Apparently the meters worked well on the beach but could sometimes read non ferrous as ferrous on land
They had plastic oversize pipe stems that contained 8x D batts in the top section drawing only around 170mA ..good for the time! and very nicely handbuilt.
They used Garretts deepseeker type 8" co axial coil housings that contained tri planar concentrics I think
Inside the box there are 2 boards like Fisher 1265's ..power and PI circuitry on the bottom board with disc on top and the components are wonderful colours!
I have one named Eileen.. hand written on the board I assume by Eric.. I did get it running again its ~85pps same as the later Minipulses and with a large pulse width I remember around 250us
Its half reverse engineered and when Ive finished I plan to put the design up here..
TX circuitry I think is standard PI design and I will post up the coil values and Fres when i find my notes

That's interesting.
I don't know anything about the Eric Foster PI discriminators. Although I understand that Eric did experiment with balanced coils on PIs to provide ferrous/non-ferrous discrimination some years ago, but there were a lot of problems with ground effect in the same way as the old TR detectors.
Or is this an early version of the Goldscan / TDI circuits?