Voodoo Main Discussion

[rickb]

To be clear, the question is about the Voovoo compared to the others.

[Elliot]

Coil size, construction ?

8" outside actual coil diameter. Spiral Litz wire with Scotch 24 shielding. The Voodoo can be compared with these (one is industry standard - Nox 800 The other is discussed on Geotech and is a good example of what anyone can build at home.

[Phantom]

Phatom - you're getting mixed up.
Carl Moreland is Carl-NC.
George Overton is Qiaozhi.

For those that don't know, "Qiaozhi" is a transliteration of "George" in Chinese Mandarin.

==========================================

I am sorry George and all the forum for the mess. I've been reviewing some issues in the ITMD and I wrote "Carl" when I should write "George"

Regards to all

Phantom

[eclipse]

Ive got the 30x38 Sef F75 coil it measures 40 ohms / 10mH and 2.2 ohms/ 0.66mH

[surfdetector]

8" outside actual coil diameter. Spiral Litz wire with Scotch 24 shielding. The Voodoo can be compared with these (one is industry standard - Nox 800 The other is discussed on Geotech and is a good example of what anyone can build at home.

I am wondering how the Raptor would fare in the comparison?

[Qiaozhi]

Hi Qiaozhi,,,Sorry about more questions,,but could you tell us what voltage ratings the Electrolytic capacitors are please? And, if the Crystal and LCD has to be a specific sort as I have a bagful of 20.000mhz crystals and some LCD 16X2 (Blue backlight) left over from other builds,,if they will do? Thanks, Marty.

The electrolytic capacitor voltage ratings do not have to be a specific value. They just need to have a rating that is above the maximum voltage they will be exposed to in the circuit. For example, the 1000uF capacitor (C1) can be rated at 16V.

On page 25 there is some information about the type of crystal required by the PIC.

The LCD is the standard 16x2 character type. Note that the connector pins on the PCB are wired as 1 to 16, but be aware that some LCDs are wired as 16, 15, and 1-14. There are also others with two rows of 8 pins that require a negative voltage for the backlight. Do not use this latter type.

[Qiaozhi]

Can you give us an idea of real world performance compared to the best PI detectors on this forum?

Rick

Things always get messy when people start comparing detectors for depth. There are too many factors to consider, such as ground conditions, coil sizes, detector type, etc., etc.

Voodoo has two modes of operation - PI and Hybrid. In hybrid mode it is designed to find targets buried in areas with a lot of ferrous trash, such as UK farmland. These are places where a standard PI is not the first weapon of choice.

We all know of detectors that can demonstrate fantastic depth on a test target in areas with no trash. Youtube is littered with such demos. However, if you test the same detector is an area infested with ferrous trash the results are extremely disappointing.

The PI detectors in this forum are either non-motion or feature a self-adjusting threshold (SAT). If you've ever experimented with changing the speed of the SAT circuit, you will have noted that maximum depth is obtained when the SAT is very very slow. Whereas in practice the detector is much more usable if the SAT is active. If you read Chapter 7 it should be clear why Voodoo is a motion detector, and how it achieves good target separation. The Voodoo concept is about finding good targets in trashy conditions, not about maximum depth. On the other hand, depth measurements are quite respectable.

As they say ... "Horses for courses".

[silverdog]

@Phantom,,,Has Silverdog received his order of boards yet? I visited the link for his shop but I can't see them available yet? Has he said he is supplying pre-programmed chips for the Voodoo or is this just a 'Maybe'? Thanks, Marty.

The boards have reached Germany so as soon as they arrive I'll add them to the shop - I ordered the battery charger boards too
I haven't programmed a PIC yet, but as long as I can I'm happy to offer those too

[MartyJ1963]

@Qiaozhi,,Thanks for the info again. @Silverdog,,,Nice one Andy,,Looking forward to you annoucing when the boards arrive and the prices. It'll be handy to be able to buy a programmed chip too as it will save a lot of builders a lot of frustration who have trouble with programmng. Thanks and regards, Marty.

[lamoiz]

@Qiaozhi,,Thanks for the info again. @Silverdog,,,Nice one Andy,,Looking forward to you annoucing when the boards arrive and the prices. It'll be handy to be able to buy a programmed chip too as it will save a lot of builders a lot of frustration who have trouble with programmng. Thanks and regards, Marty.

we are there to help us, if you have any problem for programming with the PICs I can simply do it for you ... just postage

[MartyJ1963]

Can anyone give a pat number or a link on where to buy the 20mhz 'Parallel' cut crystal please? All the items I've looked up don't say whether they are parallel cut or series cut so I dont know what to purchase. Thanks, regards, Marty.

[Qiaozhi]

Can anyone give a pat number or a link on where to buy the 20mhz 'Parallel' cut crystal please? All the items I've looked up don't say whether they are parallel cut or series cut so I dont know what to purchase. Thanks, regards, Marty.

The majority of crystals are parallel cut, so the chances are that the ones you have will work.

Apparently any crystal that is listed with a load capacitance is a parallel resonant crystal.
This attached document has some useful information.

[lamoiz]

Can anyone give a pat number or a link on where to buy the 20mhz 'Parallel' cut crystal please? All the items I've looked up don't say whether they are parallel cut or series cut so I dont know what to purchase. Thanks, regards, Marty.

https://www.ebay.fr/itm/Quartz-20-Mh...gAAOSwsW9Y3sEp
quartz hf ..

[waltr]

Can anyone give a pat number or a link on where to buy the 20mhz 'Parallel' cut crystal please? All the items I've looked up don't say whether they are parallel cut or series cut so I dont know what to purchase. Thanks, regards, Marty.

The majority of crystals are parallel cut, so the chances are that the ones you have will work.

Apparently any crystal that is listed with a load capacitance is a parallel resonant crystal.
This attached document has some useful information.

I stopped using XTALs a long time ago with PICs. What I use are ceramic resonators with built in cap.
https://www.digikey.com/en/products/...CC0A7AJiAugXyA

These are way more than accurate enough for anything we need.

[surfdetector]

I stopped using XTALs a long time ago with PICs. What I use are ceramic resonators with built in cap.
https://www.digikey.com/en/products/...CC0A7AJiAugXyA

These are way more than accurate enough for anything we need.

https://www.mouser.com/ProductDetail...vDjhgxvA%3D%3D

The price is certainly a good one.