DIY TDEM

[geowizard]

Yeppers! DIY TDEM System!

We need TWO things: Hardware and software.

1. Transmitter. $200.
2. Receiver. $200.
Microcontroller software: Free!

- Geowizard

 

[geowizard]

We already know the applications...

Treasure Hunting for Vaults.
Buried Treasure.
Gold and Silver exploration.
Airplanes buried in Glaciers.
The list goes on and on...

-Geowizard

 

[geowizard]

The Computer;

For this application, one off-the-shelf, Arduino UNO!

I won't duplicate a book on the UNO here. Readers should seek out needed info online!

Spoiler alert: The Transmitter uses 2 (two) digital i/o pins. The Receiver uses no i/o resources.

How? Stick around and find out!

- Geowizard

 

[geowizard]

The system outline;

The Transmitter transmits a bipolar square wave into the ground. To do that, the UNO drives an "H-Bridge". The H-Bridge is a switching circuit connected to a DC voltage. The voltage can be a battery.
The H-Bridge is controlled by the UNO to switch the DC voltage on positive, off, on negative, off, on positive, repeating continuously or for ten or more cycles as desired. The alternating DC voltage is applied to a transmitter coil. The coil is a single or multiple turn loop of #10 or #12 gauge wire available at any hardware store.

A multi-turn receiver coil will be used to "receive" the response from the ground.

The receiver is an oscilloscope! Portable oscilloscopes are available online at Amazon or other retail vendors. The oscilloscope needs a sweep "trigger" input. Storage is needed to store signals on a flash memory card. These functions are normally included in even low-end oscilloscopes.

Skills needed:

Assembly skills are required. Use of wire cutters, screwdrivers, and assorted basic tools are needed.
Soldering skills are minimal. It is assumed anyone involved in DIY activities has the ability to fabricate.

A basic understanding of electric and electronic circuits will help in comprehending the circuits used and assist in simple troubleshooting if needed.

Safety:

Routine workbench safety rules apply. If you are not an adult, find a qualified adult to supervise.

- Geowizard

 

[geowizard]

The system begins with a transmitter;

The transmitter timing is controlled by a "controller"!

The controller can be a simple Arduino UNO. The UNO is portable, about the size and weight of a pack of cigarettes and runs on a battery pack. I made a rechargeable battery pack using three, 3.7 Volt LiPO 18650 batteries connected in series. You can get the battery holders on Amazon and connect an appropriate adapter connector to the Arduino UNO.

Personal computer. If you are reading this, you have access to a computer.

Go to the Arduino website and download the Arduino IDE (Integrated Development Environment).

Software | Arduino

Download the Arduino IDE for Windows, macOS and Linux. Discover Arduino App Lab, Cloud, and CLI. Get the best software tools for your projects today!

www.arduino.cc

There is a short learning curve to install the IDE and add libraries. Then, you can program Arduino software with the IDE and load the software into your Arduino UNO.

- Geowizard

 

[geowizard]

If you have little or no experience, there are tutorials on the Arduino;

New projects, especially technical projects require the ambition to learn or expand on existing skills.
Arduino is part of early grade school academics! Young kids are learning to develop projects with the Arduino!

YouTube can take you from zero to 90 mph! Don't be afraid to jump right in!

- Geowizard

 

[geowizard]

Datasheet page 1;

See attachment.

Full datasheet for the Arduino uno:

https://docs.arduino.cc/resources/datasheets/A000066-datasheet.pdf

- Geowizard

 

[geowizard]

Cutting corners on cost;

Cutting corners on cost is a personal decision. There are low cost Chinese clones on the market. The original Arduino uno has full support and works predictably. Arduino is working to knock off the knock offs.

The USB interface on your computer is used to connect the Arduino for programming, power, and utilities. The Arduino driver, another download makes the Arduino connect reliably.

The USB connection gets you up and running.

There are simple programs to load built into the IDE in the "Sketches" folder. Programs are called "Sketches".

- Geowizard

 

[geowizard]

This is not intended to be a tutorial;

The process of learning is an important part of the process. The process is a personal journey! There is a lot of support out in the Arduino community.

- Geowizard

 

[russau]

To bad for me that this technology comes too late in life for me ! at 79 my options for things todo are rapidly dwindling ! My 2 "O" scopes have been collecting dust for to long just like me !

 

[geowizard]

russau,

Arduino UNO R3 Board, ATmega328P, 16MHz, USB Cable​

32KB flash, 2KB SRAM, 14 digital and 6 analog I/O, compatible with UNO R4, Mega, Leonardo, Raspberry Pi
4.04.0 out of 5 stars
(26)
Price, product page$9.88

Get a $10.00 Arduino UNO, plug it in, smile and say to self, "I plugged it in and it worked!"

Enhanced text is clickable.

- Geowizard

 

[geowizard]

Executing Blinky:

A few sketches are included in the IDE.
After downloading the FREE Arduino IDE... you can load and execute Blinky

You can smile and tell your friends, "I executed Blinky!"

- Geowizard

 

[geowizard]

Blinky is a Time domain executable;

If you can execute Blinky, You can execute a program that switches an H-bridge TDEM transmitter!

- Geowizard

 

[geowizard]

The most difficult part is the concept of a switch. Once we have mastered on and off, we can advance to having two double pole, double throw switches.

- Geowizard

 

[geowizard]

Controlling an "H Bridge";

Every remote prospector has come into contact with "H" bridges. They are used in DC to AC power inverters, motor controllers, Variable Speed Drives, inverter generators to name a few. The relatively simple circuit called an H-Bridge is the most widely used switching circuit I know of in electronics. It uses four MOSFET transistor switches configured in an "H" pattern with a "Load" connected at the middle of the "H".

Diagonal MOSFET switches are turned on or off to control the direction of current flow through the load. There are many references with detailed technical explanations on YouTube.

One of my favorite YouTube channels is Dronebot Workshop.

Driving DC Motors with Microcontrollers



We want "Blinky" to control the current flow in a transmitter loop. The loop is made from wire. Typical off-the-shelf stranded or solid 12 AWG wire will do the job. The H-bridge needs to handle 20 to 30 volts and 3 to 10 amps of current depending on your ambition. From the previous reference, the loop needs to be a square shape 10 meters on a side. Round or square makes no difference. The "area" within the loop controls the intensity of the electromagnetic field and the strength of the transmitter.

One way the energy is measured is in Newton Meters.

Energy in Newton Meters = N * I * A

N = Number of Turns of wire in the loop.
I = Amperes of current.
A = Area on square meters.

The power source (battery) is connected with positive to the top of the H bridge and negative to the bottom. The loop is connected as the load.

The source of power I decided to use is a standard Dewalt rechargeable 20 volt lithium 2 or 3 amp-hour battery. They are small (portable), off-the-shelf, efficient, weatherproof and durable for outdoor use.

Looking at the battery connector, Two spade terminal slots are available. Positive is on the left and negative is on the right. I mark the polarity on the battery to avoid getting it reversed. Reverse polarity will destroy the H-bridge.

The H-bridge has four control inputs. The objective is to apply control voltages from four output terminals on the Arduino. The Arduino can control FOUR leds. The off-the-shelf H-bridges described above have inputs that are optically isolated using leds! A slight modification of the "blinky" code will suffice to get the H-bridge working.

- Geowizard

 

[geowizard]

How long?

An H-bridge can switch transmitter currents on positive, off, on negative, off... repeating as long as we want to. We can control the length of time for each cycle. We are in control of the controller!

- Geowizard

 

[russau]

russau,

Arduino UNO R3 Board, ATmega328P, 16MHz, USB Cable​

32KB flash, 2KB SRAM, 14 digital and 6 analog I/O, compatible with UNO R4, Mega, Leonardo, Raspberry Pi
4.04.0 out of 5 stars
(26)
Price, product page$9.88

Get a $10.00 Arduino UNO, plug it in, smile and say to self, "I plugged it in and it worked!"

Enhanced text is clickable.

- Geowizard

I can't go there ! To many Dr. bill's and more to come for me and my Mrs. and my dog ! and the our 8 children ,26 Grandchildren and 6 G grandchildren OH YES before I forget the GUBERMINT and their cut ! Yha I know that I should have learned to dance !

 

[Carl-NC]

Is that it? Lots of gravy, but no meat.