I think i discoverd something (Pulse Induction working on 8.5v / 10mA)

[xpcam]

Hi Qiaozhi,

Thats true, i didnt do that yet, i wil try that today becourse im thinking im now on my limit. Ill now going to try to increase the amps a litle and use a damping resistor.

How was the video?! And the testings?!

Christian

[Qiaozhi]

The video was fine, although it is difficult to understand exactly what we're seeing without reference to a schematic. From what do I see though, you appear to be getting some ferrous/non-ferrous discrimination during the coil charging period. This is not new, and is already well documented. In fact, ITMD briefly describes this technique on page 175 under Really Advanced Topics. The difference here is that you're using a mono coil, which probably explains why the target response is fairly weak. We would need more information concerning the design before any in-depth analysis can be made, but so far I'm not really seeing anything unexpected.

[kt315]

was the signal o-scoped on preamp output or on coil directly?

[xpcam]

No and No, this was only the buffer. Didnt hook up a pre-amp yet. Qiaozhi: Soon ill buy that book. Im looking forward for it! The nicest thing i find of my proto i got it working on just a few millis and the ferro-nonferro was a free product ;-) The ferro/non-f... is easely implanteble in the pi becourse it is located at the + side not at the GND side but at de + side. If you handle the + side from the coil with care you can easely get it running. (trying with less signal loss) Oh tried with a damping, but it will blow up some parts of my board. (smoking!) I handel the coil at a different way so that a damping resistor is not possible.

Christian

was the signal o-scoped on preamp output or on coil directly?

[xpcam]

Qiaozhi: the ripple is caused by a diode.

[bklein]

You might want to try making a constant current source as a supply - set to ~10ma to see if it works. Or get a current probe for your scope...

[xpcam]

First i need to change my fets... i blew them both up, i think i used to mutch speed on the fets. (over the 6khz) i have tried some new things by running a coil on full power and a coil to read/pulse with 10mA, that was working only the depth seems to be limited. ((also with only the full current on it.) but with mutch slower pulse speed)

I didnt do mutch this week. But ill change the fets and i want to try it with some power transistors. The dual pulse field was working fine only my opamp configuration isnt. Im limited at 20cm on my knife and 30 on my iron blok even a aluminium cup can can be detected at max 30 cm. I thougt the max depth of an 8" coil would be theoretical on 32" thats around 80 cm. So a alu cup shoult be atleast be detected at 40 / 60 cm.

So i have some sensetivity problems... mayby i should try an TL071?

Still having some problems.

Christian

[chemelec]

6 Khz is Nothing for a Mosfet.
They can easly operate at 100Khz and Higher.

[kt315]

a MOSFET is not be burnt at 10mA current. that is nonsense.

[DOOLEY]

only a thought,

easiest way to destroy a mosfet is a voltage spike to the gate,
easy done.

esp when poking round with a scope probe,
one brief join between drain and gate and PUFF !!!
all gone...................
one shorted mosfet.

[6666]

Xpcam did you get this to work ?

[dbanner]

I think maybe after three years, he could have built space craft and gone to the moon.

[6666]

Yes like most projects here they start with a bang then die a natural death, just thought I would give it a shot

[Wahyu]

Hello Detector Buddy's,

I have made a VIDEO DEMO Let me know what you think?!

See youtube: https://www.youtube.com/watch?v=M83PxXD_3Ms

Statics:
V: 9v
A: 10mA
F: 2.2Khz
pW: 250uS
dt: 200uS
Stanly Knife: +/- 20 cm
Gold Ring: +/- 12 cm


Christian

Hi Christian, can you reupload please?