Popular Electronics, Feb. 1969

[mikebg]

The (R)EMI group seeks a description in English for a project published in Popular Electronics, Feb. 1969.
Carl Moreland issued the following picture of orthogonal sensing head. We found the circuit diagram and sensing head described in a Czech magazine, but it is too short and gives no information about the method of adjustment. We are looking for original description in English.

[technos]

That looks like a proto "Big Foot" coil. If somebody can't dig it up, I can as a last resort from microfilm. But it might take a while (weeks).

[ivconic]

The (R)EMI group seeks a description in English for a project published in Popular Electronics, Feb. 1969.
Carl Moreland issued the following picture of orthogonal sensing head. We found the circuit diagram and sensing head described in a Czech magazine, but it is too short and gives no information about the method of adjustment. We are looking for original description in English.

Search through patent database. I saw it once but do not remember pat number.
Go to "uspto.gov.net" and input keywords.

http://patft1.uspto.gov/netahtml/PTO/search-adv.htm

Also you must install plugin "Alternatiff" to be able to view patent pages...
I am 100% sure i saw patent that explains this coil.
Regards!

[technos]

Search through patent database. I saw it once but do not remember pat number.
Go to "uspto.gov.net" and input keywords.

http://patft1.uspto.gov/netahtml/PTO/search-adv.htm

Also you must install plugin "Alternatiff" to be able to view patent pages...
I am 100% sure i saw patent that explains this coil.
Regards!

After doing a considerable search for this article online, I could only find an abstract that mentioned that this actually uses a bridge circuit to detect a change in inductance, rather than mixing with a second oscillator. As such, it will suffer from the same limitations to depth as a BFO unlike a VLF that transmits a signal. If you look at the coil above you actually see three coils, the fourth leg of the bridge is internal to the detector. It still would be interesting to take a look at the specific circuit though.

However, I took a look at the index, and I did not see Carl Moreland's name. Leslie Huggard wrote the article, and there is another article by her in the schematics section on this site showing a design using a single lm386 with a bridge type circuit.

[mikebg]

We have the circuit diagram

We found the circuit diagram and sensing head described in a Czech magazine, but it is too short and gives no information about the method of adjustment. We are looking for original description in English.
Here is the circuit:

[WM6]

We found the circuit diagram and sensing head described in a Czech magazine, but it is too short and gives no information about the method of adjustment. We are looking for original description in English.
Here is the circuit:

Interesting schematic. Probably there are in Chech magazine Amaterske Radio some text too (about windings, coil inductance etc.)?

[Qiaozhi]

It looks similar to this one. Same coil arrangement.

[mikebg]

Thanks, Technos.
Now we know the title of article:
Leslie Huggard, Build a "Different" Metal Locator, Popular Electronics, Feb 1969.
This is drawing of sensing head:

[mikebg]

WM6,
If you are interested, here's the pages from the Czech magazine.
For us it is important to read the original in English, because we can not disentangle
- why both RX coils are connected in parallel instead in series,
- why there are two potentiometers instead only one,
- why TX coil is tuned, but both RX coils are not tuned etc.
We have called this project IBR (Induction Balanced Regenerator). This is
principle for extremely economical metal detector, which meant in our jargon as QRP MD. With a battery it will work an year!

[mikebg]

Thanks Qiaozi for pdf file.
You should know that it contains an erroneous circuit diagram of Bulgarian mine locator model MT60 or MT62. The locator is designed by Bulgarian engineers in 1960 or 1962 and made of Bulgarian transistors produced under license from a French company.
The article contains false information and was written incorrectly too. The block diagram in Fig. 1 is not
done properly and not explained correct. There are many errors in the circuit diagram Fig. 2 and coils data.
The (R)EMI group will scan the genuine documentation of MT62 and will post it in the forum.

[WM6]

WM6,
If you are interested, here's the pages from the Czech magazine.

Thank you mikebg

Here some google translation from Czech:

Atypical metal detector
This detector is based on the use of balanced -
mitted inductive bridge and is working with
low frequency signal frequency. Induktion bridge consists of two systems
coils, which are mutually perpendicular and form
input and output audio-frequency circuit
amplifiers with high amplification. When
coils so designed that in post -
bed very close to the ideal perpendicularity is the
them sufficient inductive link, which would
to introduce feedback to an extent suffi -
tangential to oscillate amplifier. When
However, the group gets close coils
metal, balance is disrupted, there is a backward
binding, an amplifier is vibrated and arises hear -
Net realizable signal. Diagram of apparatus is shown in Fig 14th
Basically, it is unstable low-frequency
amplifier with high amplification. From scheme
the obvious way system involving coils.
Because the intensity of magnetic field
distances are shrinking rapidly and the effect of metal -
tion course in this field is rapidly disappearing
with shrinkage of its size, is very ob -
Gravity to develop equipment that could zjiš -
indeed face small objects at a distance.
For detectors that are used for localization
coil ends, when the number of turns and da -
It current coil array at a distance
axis coil depends on its diameter. The
larger the diameter, thus making the field. The
However, the larger diameter coil, the greater must be
metal object from the field could not affect -
thread. For this type of detector is always necessary
use a compromise between the size of objects,
to be detected, and the distances in
to be detected.
Described detector detects aluminum ring
concluded beverage cans, or seven -
centimeter nail in depth of 5 cm. Larger
objects such as the lid of the bin, it is possible
determine the depth of 50 cm. Detector is more sensitive
for ferrous materials, because they are more
influence on the magnetic field.
When designing the electrical parts must be taken
to deploy components to the amplifier
stable, that has not been implemented parasitic neck -
between the input and output amplifiers.
Very important is the construction of sets of coils.
The main material for its mechanical
construction is wood, drawing, figure 15th In the
In addition to making non-coated wire
uses no metal. Note that both
horizontal coil with adjustable position
order to set the minimum bond.
Horizontal coils have 470 turns, vertical
coil has 870 turns. Coils are the cabinet
an electronic circuit connected coaxial cable, as shown in wiring diagram.
Popular Electronics February 1969

[Qiaozhi]

Hi WM6,

The text in the PDF file is an image. How did you get the text into the translator?

[WM6]

Hi WM6,

The text in the PDF file is an image. How did you get the text into the translator?

By search in Google again for article "Netypický detektor kovů" and instead of open it in PDF I chose open "as HTML" and then copy from html to Google translator.

[ivconic]

It is possible to use ocr, although it is not perfect. Some symbols are recognized wrong. I tried once and got 70% of text, the rest were funny symbols!!

[batman1972]

Best One!

Dear Ivconic and Friends
I'm looking for hunt gold or silver object(approximate 10*10cm size)like small
dish or rings in approximate 1m depth or a little more.pls guide me which
home made detector is the best for construct?
sorry for bad english
Thank u and goodluck