Voodoo Main Discussion

[Qiaozhi]

Did you all miss the posts from billr #1003 and #1007
where he declared himself the forum police man and he demanded that we supply him with all our information so he can complete his project
and he demanded that we all stop posting and we must obey.

The posts are on page 41 if anyone is interested.
Also, read my response in post #1006.

[billr]

George.
As I understand. Much of the concern with the project is the lack of detection range. Correct me if I am wrong.

If so. Is it not possible to add a further amp downstream to increase the signal strength at the coil whilst retaining the pickup signal on the LCD where it is? A multi layer system with boost.

Conversely. Could an additional circuit be used to alter the characteristics of the detector so that it recognizes more traditional coils with greater range than specialized coils for its purpose?

I ask because in my mechanical background it is not unfamiliar to see several stages of similar applications used to produce the desired output performance and was curious to know if this principle can be applied to electronics.

[Qiaozhi]

George.
As I understand. Much of the concern with the project is the lack of detection range. Correct me if I am wrong.

If so. Is it not possible to add a further amp downstream to increase the signal strength at the coil whilst retaining the pickup signal on the LCD where it is? A multi layer system with boost.

Conversely. Could an additional circuit be used to alter the characteristics of the detector so that it recognizes more traditional coils with greater range than specialized coils for its purpose?

I ask because in my mechanical background it is not unfamiliar to see several stages of similar applications used to produce the desired output performance and was curious to know if this principle can be applied to electronics.

I wouldn't say that it's a "matter of concern".

The intention of Voodoo was to produce a PI detector that was capable of rejecting iron, and was able to find non-ferrous targets hiding among ferrous trash.
A standard PI (one that detects all metal) will always have greater depth when compared to Voodoo because it uses a self-adjusting threshold (SAT). i.e. a slow single-differentiating filter rather than double-differentiating.

You can easily determine if a detector is non-motion (NM), single-differentiating (SDiff), or double-differentiating (DDiff) with a simple test. Hold a coin stationary a few inches from the coil. If the audio tone does not die away then the detector is NM. If it does, then it's either SDiff or DDiff. Now move the coin to one side away from the coil. If you don't get a beep it's SDiff, but if it beeps it's DDiff.

A detector with SDiff filters (or SAT) will start to detect a target as it approaches the side of the coil, whereas a detector with DDiff filters will start to detect the target as it crosses the centre of the coil. The bottom line is that the detection area is smaller for DDiff, which is why it has far better target separation than SDiff. For a standard PI, target separation is not an issue. However, for Voodoo (and for the majority of VLF detectors) DDiff is necessary to be able reduce the effects of iron masking.

In my test garden (which is littered with ferrous trash) any detector with SDiff filters, or extremely slow DDiff filters, will fail miserably when attempting to find the buried non-ferrous targets. If you use a standard PI in the test garden the audio beeping sounds like a machine gun as it detects everything.

This is why I suspect Don's variant will have difficulties with target separation due to the use of a self-adjusting threshold, and ground effect in the discriminating channel.

[6666]

billr stop sending me pm's you really are a annoying pest and troll, George how do I block this troll from sending pm's to me.

[SilverSurfer17]

I pissed in his wheaties asking to many questions old people don't like to many questions and young bucks think they know it all but anyways i got the battery together got the converter and the input voltage is 15.65 volts output voltage is 15.15 and the trimmers on the dc to dc converter does nothing to lower voltage and i got the circuit protector made also George in the book it said something about 15 volts max i think i read im gonna look again but is that 15.0 volts max

[SilverSurfer17]

I must of burnt something else out on my board when the coil got hot from that speaker TP5 and TP2 look the same with or without a TX coil connected

[SilverSurfer17]

i eliminated the 5 pin and wired it right into the pcb that inner core to positive and the ground mesh to ground and on the other end one side to one of the tx coil and the ground to the other side and have the shield and the rx disconnected and i ohmed out the cable and coil and they ohm out so its not the cable oh and i have the jig wired one end to the positive side of the coil and the other side to the ground side and nothing changes plugging in the coil or changing the resistance on the jig

[andon80]

Which program should I use to view .gbr files?

[surfdetector]

Which program should I use to view .gbr files?

You can view them online:
https://www.gerber-viewer.com/

[surfdetector]

i eliminated the 5 pin and wired it right into the pcb that inner core to positive and the ground mesh to ground and on the other end one side to one of the tx coil and the ground to the other side and have the shield and the rx disconnected and i ohmed out the cable and coil and they ohm out so its not the cable oh and i have the jig wired one end to the positive side of the coil and the other side to the ground side and nothing changes plugging in the coil or changing the resistance on the jig

Disconnect the coil. Put a damping resistor across the PL1 (TX) . Then on channel one, take your probe and connect to one side of the damping resistor and put your ground to the ground side of the resistor. For channel two attach to the TP2 Debug and trigger the scope from channel 2. This will show that the transmit is working properly. I show this in my Part #2 video.

[Qiaozhi]

... but is that 15.0 volts max

Yes, that's the maximum input voltage for the LT1054.
You're making things more complicated than they need to be. Why don't you use 10x NiMH AA batteries as specified?

[Qiaozhi]

Which program should I use to view .gbr files?

You can view them online:
https://www.gerber-viewer.com/

There are several available, but I use Gerbv -> https://sourceforge.net/projects/gerbv/

[SilverSurfer17]

Because i had brand new 18650 batteries already when i checked it i ran the battery down below 15 volts with just the led for awhile before i checked it to make sure i didn't toast anything going over to 15.17 volts i can run it off of 11.1 volts if thats the problem but i dont think thats whats wrong i think when the speaker was plugged in and that coil got hot it fried something

[andon80]

You can view them online:
https://www.gerber-viewer.com/

Thank you for your interest
Surfdetector
George

[andon80]

I've been able to finish the voodoo circuit and test it in the field
I bought the book. Installation will start when pcbs come in a week
I wondered the performance of the circuit