IDX-PRO+VDI

[ampirate]

Question, could a Transistor be failing ?

I think i shorted the Coils out a few times while trying to tune with the Caps.

Which of the TX and RX Transistors might be susceptible to damage - if one of the Coils was shorted ?

-

Tuning and Nulling:

1. The Scope is not very helpful because the Scope is only Single Channel,

2. I dont get to the point of using the Scope - because I start Tuning by Detector Buzzer Sound while shifting the Coil Positiuon,
but the more that I center it to a Sensitive position - the more the Buzzer continuously Clicks and Buzzes
- like the Detector is going crazy and Chattering on its own.

I can hear the Response while i move a target back and forth ,
mixed in ,
but the Chattering Noise is independently overlapping - like someone else is pounding a morse code key.
so, its hard to clearly identify what is Target Response and what is Noise.

i cant Tune the detector by sound - while blasting a stereo - no ?

[ampirate]

Question, could a Transistor be failing ?

i cant Tune the detector by sound - while blasting a stereo - no ?

Added the 100nf across u1 5534 p4 to p7.
And, I tried replacing lm358 and 5534 - no difference ...

With NO Target still sounds like a crazy morse code radio or crazy cricket or cicada or woodpecker - buzzz beep beeep buzzzzzzzz beep buzz buzzzzz ...
I cant tell the difference the Target Response and the annoying locust sounds ..

-

This is supposed to be a straightforward kit from silverdog.

But so far for weeks now - I have had miniimal to no luck scanning for coins or even a Can on the floor with this Detector ...
I get 1 foot or less for Coins in Air and Zero on the floor.

I have better luck with the 8 transistor Metal Detector - that I slapped together for my 5-year old daughter.
At least I (or she) can take her Detector outside and not feel embaresed.

-

I left the Scope readings on here as requested ... is this any help ?

Understand that I am a Digital EE engineer - things work or not - I could never get down fidgeting to get a radio project working ...

[ampirate]

This is the second time that I attempted this IDX Pro VDI Project.

The first time, i etched the board myself , as I showed on previous pages
- but still could not get full functionality then either.

[porkluvr]

Even with only a single channel scope you may be able to chase down the source of chirping. Start back at the speaker transistor and work towards the front to try to see which channel(s) the noise is propogating through. Be aware that it is possible that simply probing a point on the PCB may be enough to quash any oscillations that may be taking place and things could get quiet. If that happens you should pay close attention to the area you are probing.

Be sure and look at the power supply lines and if you see noise that correlates to the chirps. You would need to try to determine whether the power supply caused the noise or if the noise source causes blips on your power lines. "Which comes first the chicken or the egg" may not be simple to figure out.

[ampirate]

Even with only a single channel scope you may be able to chase down the source of chirping. Start back at the speaker transistor and work towards the front to try to see which channel(s) the noise is propogating through. Be aware that it is possible that simply probing a point on the PCB may be enough to quash any oscillations that may be taking place and things could get quiet. If that happens you should pay close attention to the area you are probing.

Be sure and look at the power supply lines and if you see noise that correlates to the chirps. You would need to try to determine whether the power supply caused the noise or if the noise source causes blips on your power lines. "Which comes first the chicken or the egg" may not be simple to figure out.

Mpsa13 to Speaker - tweets/pulse/spike 2V only with Noise.
Mpsa13 Base - tweets/pulse/spike 2V only with Noise.
Bc547 Collector to Mpsa13 Base - tweets/pulse/spike 2V only with Noise.100k resistor to U7 Lm393 Pin1 - Continuously oscillates as Square wave ALWAYS.
Bc547 Base to 100K Resistor - Stops ALL tweets with Scope connected.

U6 Lm358 p3 - tweets/spikes 2V with Noise
U6 Lm358 p2 - Nothing.
U6 p4 - Nothing.
U6 p8 - Nothing.

U4 P7 - tweets/pulses 2V with Noise
U4 p5 - Pulses 2mV - 10mV p2p with Noise.
U4 p6 - Nothing.

U3 p1 - Pulses 10mV-20mV p2p with Noise.
U3 p2 - Nothing.
U3 p3 - Nothing.
U3 p14 - Pulses 10mV-20mV p2p with Noise.
U3 p13 - Nothing.
U3 p12 - Nothing
* tying U3 p12 to p13 turns off Noise and Target Response.

Power Supply Bats & V - No osc.
Reg - show no oscillation.

[der_fisherman]

Setting up Electroncs for Metal Detecting with and without an Ocilloscope

I did read somewhere about setting up the on the IGSL blog (I believe!) with a single channel scope, but please don't ask me where in that blog, also I never tried it......nor do I know how good/effective it is either....

Some people without a scope use a good multimeter and look for the lowest voltage on an Induction Balance Metal Detector from the receive coil, though in this case, I would expect an old fashioned "needle meter" type to be better as its "readable" even while swinging from side to side....a modern digital meter will be mostly unreadable, unless it has an analogue display as well, now that might be ok. Some on geotech use them. I do not know if a needle type meter can read down to 3 or 4 milli volts or not, sorry, its such a long time since I used one.....

Phasing is difficult to set up with no dual channel scope though....

A secondhand scope from ebay ( I have no idea where you live or that is practical, sorry!), or borrow one (be careful!!) could be a solution.

Also a possibility, (but you must be careful reading tests online to check quality first!) one of those USB to PC scopes might do it.....there is a really cheap one from PICAXE that I intend to buy myself and make sometime just for fun, as I have a normal 2 channel scope myself....(not meaning to gloat!!). There is a lot of rubbish around on the internet with a USB connection, or so I have been told....

But we don't need high speed in our hobby, they should be all fast enough, but do check up fully before buying!! (...and don't blame me!!)

See here for example:-

http://www.picaxe.com/Project-Galler...-Oscilloscope/

http://www.picaxe.com/Hardware/Add-on-Modules/PCB-scope/[/url]

You may also find this interesting for other reasons:-

http://www.picaxe.com/Project-Gallery/Simplest-Digital-Frequency-Counter-08M2/[/url]

Sadly I have not yet built or used any of them....If I do, I will post my findings here......as I am sure others also will....

There are even PC sound card scopes, which some use seemingly, in the low frequency area of metal detectors. Try looking here:-

http://www.zelscope.com/[/url]

Its free too I believe!! Financially it equals a low level of investment......probes and interface of some sort!!! And its dual channel too!!

I have no idea how good it is, but its been around for 8 years or so, lots of updates and improvements I understand!! Here is what they say:-

Zelscope is a Windows software that converts your PC into a dual-trace storage oscilloscope and spectrum analyzer. It uses your computer's sound card as analog-to-digital converter, presenting a real-time waveform or spectrum of the signal - which can be music, speech, or output from an electronic circuit. Zelscope features the interface of a traditional oscilloscope, with conventional gain, offset, timebase, and trigger controls. As a real-time spectrum analyzer, Zelscope can display the amplitude and phase components of the spectrum.

General features
- Responsive real-time display, up to 50 fps refresh
- Single trace, dual trace, and XY (Lissajous) modes
- Bandwidth: 10 Hz - 20 kHz, AC coupling
- Timebase: 10 us - 5 s
- 8-bit and 16-bit acquisition, 11 kHz to 44 kHz sampling rate
- Spectrum analyzer: amplitude and/or phase
System requirements
- 300 MHz or faster PC, 64MB RAM, 1MB of disk space
- Windows® XP
- sound card
Data export
- Raw data export as WAV file
- Screenshots can be saved in BMP and EMF formats
- Visible trace(s) can be saved as text file
- Copy-paste function for screenshots or data files
- Printing
Triggering
- Adjustable trigger level, slope, and delay
- Pretrigger view
- Single shot triggering mode
On-screen measurement
- Two cursors set by left and right click
- Voltage and time difference readout
- Direct frequency readout

You might be willing to fully test this version for us here if nobody else has done it already!!! Its biggest drawback is WinXP, but all the programs I have installed on Win7, that were written for XP all work!! It probably will not work on Vista or Win8.x though.....

I hope this helps and stimulates you further....

Regards

Andy

[der_fisherman]

Possible areas to check are underlined....with that great advice...

Mpsa13 to Speaker - tweets/pulse/spike 2V only with Noise.
Mpsa13 Base - tweets/pulse/spike 2V only with Noise.
Bc547 Collector to Mpsa13 Base - tweets/pulse/spike 2V only with Noise.100k resistor to U7 Lm393 Pin1 - Continuously oscillates as Square wave ALWAYS.
Bc547 Base to 100K Resistor - Stops ALL tweets with Scope connected.

U6 Lm358 p3 - tweets/spikes 2V with Noise[/U]
U6 Lm358 p2 - Nothing.
U6 p4 - Nothing.
U6 p8 - Nothing.

U4 P7 - tweets/pulses 2V with Noise
U4 p5 - Pulses 2mV - 10mV p2p with Noise.
U4 p6 - Nothing.

U3 p1 - Pulses 2mV - 10mV p2p with Noise.
U3 p2 - nothing.
U3 p3 - nothing.

Power Supply Bats & V - No osc.
Reg - show no oscillation.

Nice of someone to make up that great list for you I feel....it should really help.

Firstly, clean PCB with spirits and an old toothbrush to get off any deposits of solder flux....I use cheap Methylated alcohol from a supermarket, works great and does not take off markings in my experience. Check with a magnifying glass that its really all gone.
Check components are correct values and correctly orientated. I find sometimes that the value of a component is correct, but it is higher/lower than it should be!! My failure. If a kit, there maybe two errors of placing. 4.7 KOhms, instead of 470 Ohms for example.....check check and check...lift one leg and measure with Ohmmeter all of them!!
Identify all caps 101%, measure too if you have such a meter BEFORE installing next time!! All parts.
Look for dry joints, pop the iron on hot and melt each one quickly again....and away!!! Remove excess solder carefully....
Look for cracks in the PCB with a strong magnifier/microscope. Solder over them if found.

Best of luck

Andy

[ampirate]

Current tuning :

iron screw - 6 inch
ferite - 6 inch
aluminum coin - 2 inch
brass - 2 inch
Magnet - 10 inch
aluminum can - 12 inch

I followed up and down the instructions for building the Coil.
I have 6 assorted TX and RX coils for this project.

- i have about a dozen coils that i built for other detectors with some success.

What is so complicated about this ?
I twisted a TX coil of 0.7mm of a circumf of 69-70cm of 35 Windings with 1uf Cap for 35cm DD coil.
I twisted a RX coil of 0.2mm of a circumf of 69-70cm of 269 Windings with 0.033uf Cap for 35cm DD coil.

I have also earlier tried :
TX coil of 128cm circumf with 24 windings of 0.7mm.
TX coil of 78-80cm circumf of 0.7mm wire of 35 windings
RX coil of 78-80cm circumf of 0.2mm Wire of 255 Windings

There shoul;d be Sizes and Values and Caps for these - not just maybe this or that ...

[golfnut]

You need to adjust the overlap of you coils to get lower amount of signal at preamp output.

( Your preamp is saturating - signal heavily clipped ) You do this with scop attached - on preamp output.



-----

Your Tx looks a touch triangular - which is a new one for me... Normally look like this .


====


From earlier pic, looked like the foil wrap screen was loose, normally put buffer pvc tape on coil, then foil, then protective layer of tape.


DID you foil have a gap in it???

You cant wrap all of the coil!! Needs gap. sorry if u did already..


-----


you mentioned you get ferrite at 6" ----- you want to NOT get the ferrite, as Im sure your aware. When u dont get the ferrite, but get every other non ferrous metal - your initial phase of the leaked/residual Rx signal ( from the preamp output ) must be in the correct phase relation to the Tx wave.

[ampirate]

Last Tuning Readings :

Coins - 25-30cm
Brass 2cm - 20cm
Iron Screw 3cm - 30cm
Small 1cm Ferrite - 20cm
Aluminum Foil - 20cm
Tin Can 12cmx8cm - 65cm
Steel Washer 1.5cm - 20cm
Magnet 1.5cm - 15cm
Copper plate 3cm - 15cm

And, Rattling like a sleepy Cricket with Random Noise.

yeah, i know, adjust to NO Response for Ferite.

I am aiming for VDI (which is tested as ready and waitiing with arduino) - so I need ZERO Noise.

[golfnut]

the coin distance sound right.

dont know if u can reject ferrite.??

do u have a gap in youe screens.

Your Tx screen and Rx screen should not touch

The sheild wraps should be not floating, but secure.

[onuba]

can i put arduino vdi Connection V3 x pin.1 and pin.14

I am with this project is finished and I want to ensure coxecione Thanks

[golfnut]

i would go for 7,8 keep the measurement of linear signals, the vdi wont "see " small targets (same as a deus)

with 1,14 the geb on 14 is will be non linear due to diode feedback. so the integrity of the phase relation gets lost.

[onuba]

i would go for 7,8 keep the measurement of linear signals, the vdi wont "see " small targets (same as a deus)

with 1,14 the geb on 14 is will be non linear due to diode feedback. so the integrity of the phase relation gets lost.

will do the connection at pin 7 and 8 of V3, Thanks golfnut

[ampirate]

I am using the Silverdog pcb.
Are there any mods on this that might help with the Noise problem ?

What is the use of VR2 and P6 ?
Should I add these to the board ?