Voodoo Main Discussion

[Qiaozhi]

G'Day Qiaozhi
Thanks for the files REV-C.zip file only contains Gerber files to make the pcb. The zip doesn't contain the schematic that were used to create the Gerber files
Ivconics sch file is not compatible with KICad it is either Protel or Eagle

The original EasyPC project, schematic and PCB are definitely contained in the zip file.
They have the extensions: prj, sch and pcb. Of course, you will need EasyPC to read them.

If you want to create your own version, then I would use KiCad.

[phred01]

Having studied the circuit noticed the whole circuit uses positive as ground like old British cars. Is there a logical reason for this approach?

[Qiaozhi]

Having studied the circuit noticed the whole circuit uses positive as ground like old British cars. Is there a logical reason for this approach?

Carl's Hammerhead design also uses battery positive as ground (0V).
In Chapter 2 it explains that the Voodoo Project started as an experiment to combine Hammerhead and Raptor (a VLF design from ITMD) as a means of providing ferrous/non-ferrous discrimination.
It's just a different power supply topology. The Arduino Nano PI Project (ANPI), for example, uses a more conventional approach.

[Carl-NC]

Having studied the circuit noticed the whole circuit uses positive as ground like old British cars. Is there a logical reason for this approach?

In a typical PI, the battery voltage is applied to the coil and then, when it's removed, you want the coil to decay to ground potential. When using a low-side switch, if the coil is connected to ground then the switch must be connected to -V. The easiest solution is to just relabel the battery so the + side is ground.

[phred01]

Happy New yr to all.
There are 2 a ways to control the current in the TX coil. In the Voodoo case, the case it is source side of the power FET. What is across after turn on pulse is a ringing coil with a loading 1k and 2 diodes. In the MPS PI - Iron discriminating metal detector design the coil is on the drain side of the FET with 300 ohm permanently across it. The difference with the Voodoo case TX & RX coils are both used to receive echo signals from the target. Where as in the MPS-PI only the RX coil is used;. The MineLab metal detectors use a complex cct capacitor diodes to quench the back EMF to about 185 v The inputs of the receive op amps have 2 FETs to prevent of being fried. The only downside of the Voodoo design I see is the digital side is a little bit harder to debug in case of a problem. So far in my view the Voodoo approach is novel.

[kraimov]

Good work thanks

[Voyager]

Hey kraimov, why are you using my signature?

[scs-bg]

I made a hybrid pulse detector 20 years ago, long before Voodoo. It turned out that due to the influence of the ground, incorrect discrimination of deep-lying objects occurs.

[scs-bg]

The best working hybrid detector is with a DD coil. Sound from a pulse induction channel. Discriminator with a meter with an arrow. Separate channel, signal when transmitting. Both channels without movement, with a reset button. Both channels work with a signal from the receiving coil. In this way, the influence of the ground is weak and a great depth is achieved. Frequency 220 hertz.