Voodoo Main Discussion

[SilverSurfer17]

Whats left after i figure out whats wrong tuning it and i understand it its pulsing a signal with pi and receiving with vlf i wanted to make just a mono coil and im curious And inside the metal detector isn't going to fix my voodoo and like i said before im not the only one who asks questions but thats cool ill replace every single part until i do get it working why is it when the same question is asked by someone else you don't tell them go read itmd just me

[Sean_Goddard]

I found some resistors that ohm out less then others like 100k that settled down at 67 while all the others of the same ohm where at 99 so those resistors are bad that ohmed out less ? I found a few other ones also that ohm out less then the same exact resistor

Are you measuring these 100k's in circuit? Please bear in mind that there will be many paths which will cause low readings.

Resistors NEVER fail low value, always high. If they are marked 100k and measure lower OUT of circuit then blame the place you bought them from.

I am at a loss as to why people have so many problems with these projects. I bought a Surf PI, worked first time. Baracuda, first time. TGSL, first time and now a Voodoo. PLEASE build each stage as listed, ALWAYS PSU FIRST. Then check for correct operation. In this case a signal generator can be used to drive the negative generator to test. If your PSU isn't working properly, you will have nothing but problems with the rest of a build, AND if you build in stages and some part doesn't work, fault location is a doddle. Look up GOLDFINDERS Voodoo build on YouTube. How it SHOULD be done.

Just read Walter's post above.. Stupid me.

I'm considering one of these CS5361 as my ADC, 24bit, 114dB range and X2, x4, x8 switched gains for a total Dynamic range of 123dB. Should be interesting.

[waltr]

I found some resistors that ohm out less then others like 100k that settled down at 67 while all the others of the same ohm where at 99 so those resistors are bad that ohmed out less ? I found a few other ones also that ohm out less then the same exact resistor

Are the resistors you are measuring in-circuit (still soldered on the board)??
If so then due to connections they will measure lower. They are essentially in parallel with other resistances.

Also, when in circuit and the measured resistance 'drifts' this means that there is a cap in the circuit that is being charged by the Ohmmeter.

Resistors measured in circuit is not a totally reliable method to assess actual value. This does work to find resistor that are open or shorted but not actual value.

[Qiaozhi]

I realise the Voodoo is a PROOF OF CONCEPT (not that there was ever any doubt George would find a solution). I am talking about developing the idea further to gain more performance. I'll probably fail, but I'm going to see if it is possible.

I have a few analogue and digital design trick up my sleeve that I can apply. See where I get to, but FIRST..... I'm going to build a stock Voodoo and see how it performs.

I'm NOT knocking the design, it's wonderful, but I want to play with it, see what is possible.

I never for one moment thought you were knocking the design.
You are doing exactly what I hoped others would do. That is, to take the concept and try and improve it. After all that's what we like to do here ... isn't it?

[Sean_Goddard]

I realise the Voodoo is a PROOF OF CONCEPT (not that there was ever any doubt George would find a solution). I am talking about developing the idea further to gain more performance. I'll probably fail, but I'm going to see if it is possible.

I have a few analogue and digital design trick up my sleeve that I can apply. See where I get to, but FIRST..... I'm going to build a stock Voodoo and see how it performs.

I'm NOT knocking the design, it's wonderful, but I want to play with it, see what is possible.

[Qiaozhi]

George should i make a mono coil of a certain inductance to match the basic settings like to match the tx loop of troy coil this is what ive been messing with its 20 gauge and a 8 inch i dont have a cap installed i have lots of 20 gauge magnet wire

From reading your numerous posts concerning the struggles you're having with the Voodoo Project, it is obvious that you don't understand the basic workings of a pulse induction metal detector, let alone the complexities of a hybrid design. I would seriously suggest that you get a copy of Inside the METAL DETECTOR, and then read and absorb the information before proceeding further, as it would help to preserve the sanity of both yourself and other Geotech members.

[SilverSurfer17]

I found some resistors that ohm out less then others like 100k that settled down at 67 while all the others of the same ohm where at 99 so those resistors are bad that ohmed out less ? I found a few other ones also that ohm out less then the same exact resistor

[SilverSurfer17]

George should i make a mono coil of a certain inductance to match the basic settings like to match the tx loop of troy coil this is what ive been messing with its 20 gauge and a 8 inch i dont have a cap installed i have lots of 20 gauge magnet wire

[SilverSurfer17]

Yeah the videos i watched where showing more how to use it didnt even mention calibrating the probes or about grounding i realized it was even a ground because of Surf’s video i was like wtf i must have to have that clip connected and found out not while using a power supply the first and last time i used one was back in 1993 my teacher in auto class showed us how to use one for looking at fuel injector pulses but he didnt show how to calibrate it or that it even had to be i do remember him mentioning the ground but that was like 3 decades ago lol

[SilverSurfer17]

how do i flip this around to look like in the book that looks like 90% of the battle ?

[SilverSurfer17]

Ok surf thanks that was part of the problem plus i had the prob on backwards on the resistor jig now it looks just like yours did in the video so the transmit portion works now what this is where im running into trouble checking it with a mono coil it doesnt beep it doesnt look right for the wave forms but sometimes i can see the wave move when i run metal by the loop

[Matt_Rowe]

[ATTACH]54563[/ATTACH]Ok back to where i was at the start no tx coil connected and only the jig connected to the tx channel and its the same as it was before using the ac to dc power supply but it looks backward still even using dc

pages 28 to 32 in the book maybe will help, not sure

[SilverSurfer17]

Ok back to where i was at the start no tx coil connected and only the jig connected to the tx channel and its the same as it was before using the ac to dc power supply but it looks backward still even using dc

[Matt_Rowe]

No i never checked each part individually ive never had to in the past but then again i assembled and tested not had to fix boards so i can figure some things out i barely even know how to use this oscilloscope lol

I have only seen scopes and never used one, so i got one for free, and the first thing i did was download the manual, looked up how to set it up and basic use, then watched a couple vids on you tube about scopes, how to use, set up, do a simple square wave, and make sure ho w to hook up probes and especially about the ground on the probe and when not to hook it up, and where to hook it up.

[Matt_Rowe]

No i never checked each part individually ive never had to in the past but then again i assembled and tested not had to fix boards so i can figure some things out i barely even know how to use this oscilloscope lol

Did you check each step as you built the board, if not, how do you know you dont have a new faulty part