GOLDSCAN 5 SCHEMATIC QUESTION

[daverave]

im also thinking about making another TDI this winter with a few mods to get lower noise and lighter design...without using SM components....my second TDI i made has a delay of 8 uS which has made it even more sensitive to tiny items.

[Orbit]

This table I need to draw will be in sm components, i prefer my pcb to look smaller.like the previous two versions one I think I posted pictures and the second version in sm I did not each has some differences, and you know that little difference means a lot!

[6666]

Of course,and now I'm drawing a TDI -SL original, I intend to draw several versions, one will be with bipolar transmission similar to fisher impulses!
otherwise on the drawing is TDI -PRO except I use my controller and little modification in the power supply and I don't use an integrated circuit for sound as with pro already from the TDA family- ....I can set different times with my controller and a frequency of 800hz to 3.3khz..I have drafts of several versions from the original to my modifications which mainly relate to noise reduction!

Hello Orbit will you be posting any information or drawings here ?

[6666]

im also thinking about making another TDI this winter with a few mods to get lower noise and lighter design...without using SM components....my second TDI i made has a delay of 8 uS which has made it even more sensitive to tiny items.

Hi Dave, congrats on getting a TDI built and working, they are not an easy build, would you mind saying which timings you used ? thanks

[daverave]

my detector based on conventional tdi pro...i have not used a micro processor...and detector works very well on the beach and detects very tiny items...my next project will improve a bit more and lighter design.

[6666]

my detector based on conventional tdi pro...i have not used a micro processor...and detector works very well on the beach and detects very tiny items...my next project will improve a bit more and lighter design.

Thanks Dave, had any good finds ?

[daverave]

my wife found a nice palladium ring with the tdi pro...my wife has become better than me in finding rings...maybe she got more patience than me

[daverave]

when you say about bipolar transmission similar to fisher...are you refering to the old fisher impulse or their latest AQ ???

[ivconic]

my wife found a nice palladium ring with the tdi pro...my wife has become better than me in finding rings...maybe she got more patience than me

Patience is the key word.
We keep forgetting simple truth; it is the person who find the finds: not detector.

[DELAY888]

A great phrase

[daverave]

whats the advantage of using a bi polar coil drive in a pulse detector ????

[Qiaozhi]

whats the advantage of using a bi polar coil drive in a pulse detector ????

1) It automatically removes Earth field effect (EFE) so no need to generate a secondary (late) sample pulse to subtract from the main sample pulse. This is because the polarity of the Earth's field is the same for both positive and negative TX pulses.

2) Since the polarity of the pulse is constantly reversing, it minimizes the problem of magnetizing the ground. This is also important when searching for landmines, as some of these can be triggered when they detect a constant magnetic field.

3) As there's no requirement for the secondary EFE sample pulse, the TX pulse rate can be greatly increased. This is useful when searching for small low conductive targets such as gold nuggets.

[daverave]

Hello Qiaozhi....when you say a bi polar coil drive minimizes the problem of magnetizig the ground so does that work the same for wet sand and does that allow the use of lower delays without chatter on the wet sand...also does anyone have a diagram of a bi polar coil drive that can be used for any pulse detector.

[Qiaozhi]

Hello Qiaozhi....when you say a bi polar coil drive minimizes the problem of magnetizig the ground so does that work the same for wet sand and does that allow the use of lower delays without chatter on the wet sand...also does anyone have a diagram of a bi polar coil drive that can be used for any pulse detector.

Bipolar drive will not cure chatter from wet sand. The salt in the wet sand looks like a low conductivity target to the detector. Salt is sodium chloride, and sodium is a metal. Increasing the sample delay will allow you to ignore it.

[daverave]

i have modified two of my detectors to work down to 8 uS and work fine on the dry sand but on the wet sand too much chatter and thats why i wondered if a bi polar coil drive would eliminate the chatter at low delays...so is it only on inland field sites that the bi polar coil system will eliminate the ferrous ground effect ???