Vallon VMH3CS Mine Detector

[Ferric Toes]

Yes I use the quick compensation at times too when the machine false signals for no apparent reason....
I do wonder if it does need to be ground balanced again when the sensitivity is changed....Hopefully Eric has an answer
Intuition tells me that if you make the thing more sensitive, then it would be more sensitive to ground noise also....so another GB may do the trick...

Not knowing how the ground balancing works, it is difficult to answer with any certainty. Since the detector is affected more by EM noise at higher settings, it seems logical to assume that ground noise will increase also. In an area where the ground is quiet it maybe beneficial to GB at the higher sensitivity and then switching down to default gain should maintain an improved GB.

It is reported by others, and confirmed by myself, that Australian ground in noisier in the heat of day and quieter at night when the ground cools down. After rain, the ground is also quiet. This is because the heated ironstone on the surface shifts it's time constant slightly compared to the ground that is in shadow or buried. For gravelly ground in the sun you end up with a spread of TC's which the GB cannot balance optimally. At night it all cools to about the same temperature and if it rains, even more so, and the spread of TC's is at a minimum. Hence less noise.

I have confirmed this effect in the lab by heating and cooling samples of ironstone and plotting the decay time.

Eric.

[tifred]

thank you Brian

[Mdtoday]

For anyone in OZ looking for the 6 pin connector Eric was referring to in earlier posts about audio adapters (UTS6JC10E6) was quoted.
It is available from Element14

http://au.element14.com/souriau/uts6jc10e6p/plug-hiseal-size10-6way-pin/dp/1795870

Brian

[Mdtoday]

Hi Carolina,
Thanks for asking,at least we know now.

I'm going to turn my attention to the audio output as the sound is too harsh for me, screaming banshee noises aren't my thing
Thinking of doing one of Eric's headphone mods and adding a circuit to shift the audio frequency range down a little as I find it hard to hear the high pitch...a by product of years of guitar amps in my ears..

Brian

[Carolina]

Brian: Talked with my man about the missing tag and turns out there was no tag in the first place. This is a Pre-designated area for a military IUID tag. The Brit's chose a different size and location for their tags. It is the small tag with the 2 D barcode beside the
VALLON date & serial number tag.

[Mdtoday]

Apologies, should have said, RS232 voltages are correct so nothing wrong with the port.
Essentially, it transmits 0 and waits...for what character(s) that is the question

Brian

[Mdtoday]

I had another quick look a the RS232 communications IO tonight and there is not much to report unfortunately.
The TX pin just cycles once on switch on as per attached pic.
After switch on, pin toggles to -5v for 340ms then pulses to +5v for 180ms and returns to -5v and stays there.
I did try a few different combinations of baud rates etc but no change.
Even tried holding down different push button and combinations on power up but still the same.
Ill try a few more options but without a protocol or sequence its going to be difficult.
It may be this particular unit, might be this series does not have RS232 enabled.
If someone else could try and have a look at the waveform, see if it matches then it would help narrow things down.


Brian

[Mdtoday]

I would be interested if you do go further with your investigations. I don't have a FTDI usb dongle, only CP2102. I would not know where to start, to just get some basic logging facility running. Though page 36 of the Ver 1.14 manual might offer some small insight to get a handshake going.

Hi Greylourie,

Thanks for the info, yes I downloaded the software, read the manual and came to same conclusion.
The data acquisition rate according to Vallon, is 40Hz but it is not clear if this is packets of information or single samples.
The data output could possibly be activated by a certain key sequence too but that is just a guess and of course the danger of doing this is that the boot-loader may then be activated and it's possible to brick the firmware if you are not careful, not good
I'm sure Vallon would have protected and locked things away to prevent misuse given the nature of the product but I'll dig around and see what info is freely available and not commercially sensitive.
I'll know a bit more once I hook up proper connections.
Maybe someone else has already tried this and would like to comment.
Either way, I'll post up the outcome

Brian

[greylourie]

RS232 Output.

Hello Brian,

I downloaded and installed the VEVA2000 program from Vallon. But on startup, it brings up a small warning box with the comment, " No valid Dongle found!. Application will be started in Demo-Mode!"
A look at this download directory : http://www.vallon.de/pdf/download/ shows several files available. An interesting but dated (last modified 2007) zipped file "Dongle Manual Install GUI.zip" contains amongst other things, a html doc "readme" that mentions a Hardlock key. This key, I assume to be the dongle mentioned at startup of the VEVA program. So, it looks like that avenue is closed. Pity, because according to the brochure for the program, it appeared to have a lot of useful things bundled together.

I would be interested if you do go further with your investigations. I don't have a FTDI usb dongle, only CP2102. I would not know where to start, to just get some basic logging facility running. Though page 36 of the Ver 1.14 manual might offer some small insight to get a handshake going.

[Mdtoday]

I fixed the twisted housing issue quite easily thanks to Eric's suggestion, looks much better.
Had the scope out for another project so thought I would take a peek at the serial data lines to see if they were active.
I didn't connect to RS232 port on my computer as it was getting late and I have no idea if the boot loader is active and didn't want to chance corrupting program memory.
However, A quick look at the TX line, at power up, it pulls up to roughly 5v then a few ms later pulses low then returns to 5v.
no other activity.
Ill setup with a terminal program and proper connections when I get time and try a few things out

Brian

[kingswood]

Hi Carolina,
Ok gotcha, yes I see the area you are talking about now, hopefully your friend can shed some light on this.
I think I will read the manual a bit more as I'm not even familiar with the quick compensation

Kingswood was asking about re-ground balancing after changing sensitivity so maybe this is the answer.

Brian

Yes I use the quick compensation at times too when the machine false signals for no apparent reason....
I do wonder if it does need to be ground balanced again when the sensitivity is changed....Hopefully Eric has an answer
Intuition tells me that if you make the thing more sensitive, then it would be more sensitive to ground noise also....so another GB may do the trick...

[Mdtoday]

Brian: The red tape may very well be to stop the arm cuff from moving. The clean spot was definitely something applied across the body of the detector. Mine was exactly the size and shape of yours. Both my detectors are missing those tags on the body opposite from the date and serial # side. One detector is 7/2009 the other 7/ 2010. I have a friend who can tell me what the missing tags are. Will talk with him tomorrow. Sometimes when my detector gets chatty, I just use the quick compensation to calm it down.

Hi Carolina,
Ok gotcha, yes I see the area you are talking about now, hopefully your friend can shed some light on this.
I think I will read the manual a bit more as I'm not even familiar with the quick compensation

Kingswood was asking about re-ground balancing after changing sensitivity so maybe this is the answer.

Brian

[Carolina]

Brian: The red tape may very well be to stop the arm cuff from moving. The clean spot was definitely something applied across the body of the detector. Mine was exactly the size and shape of yours. Both my detectors are missing those tags on the body opposite from the date and serial # side. One detector is 7/2009 the other 7/ 2010. I have a friend who can tell me what the missing tags are. Will talk with him tomorrow. Sometimes when my detector gets chatty, I just use the quick compensation to calm it down.

[Mdtoday]

Good info Brian
In my experience of trying to increase the sensitivity, I just get increased false signals, which I think is related to ground mineralisation. Thinking about this now though, when I have increased sensitivity while detecting, I havent then re-ground balanced....I dont know if I should re-balance when I increase the sensitvity....Dont know enough about PI detectors to know if I should!
I will try this though!

Hi Kingswood,

Yes, good point, I will try a few different things too and see where the happy medium is.
Intuitively, I would say yes but not knowing how the circuit/firmware takes care of its ground balancing it's probably best to just try it.
This is something Eric may be able to answer with his experience on the Vallon so far.

Brian

[Mdtoday]

Eric and Brian: Upon further investigation I have determined it is not a stain left from the UXO red lable. I own two VALLONS and one has this same clean spot as yours. Does not match the size of the red UXO label though. Now I'm curious what it's from. Also never seen the red on the battery tube. I wonder if the soldier was issued his own detector and this was a way to identify his machine as it appears, at least in my instance, the fabric back pacs appeared not to be used. One of my detectors looked like it fell of a truck several times. I don't think the cases were used much.

Hi Carolina,

Interesting, I just thought the red tape might have been used to stop the arm cradle from slipping, so didn't think much more about it.
Its a May 2010 build and I also noticed a missing label from the opposite side of body from serial number is missing /removed.

Brian