There are actually many different reasons why you should build your own homemade PI (Pulse Inductive) metal detector. But above all, it can save you money and offers less risk of wasting your money in buying a commercial detector that you may end up finding nothing in return.

In fact, there are several homemade detectors out there that has better sensitivity or accuracy than those metal detectors being sold in the market costing from around $1000 and up.

Although, before you decide to build your own detector it is highly advised that you should have good “knowledge” and “skill” in electronics. Many people actually ends up being frustrated because they can’t troubleshoot their project to work correctly. So if you do not have any idea about capacitors, resistors and transistors then you really have a big problem. Anyway, if you have a friend or family members who got the skill then you can always ask for their help.

PI (Pulse Inductive) Metal Detector

Unlike VLF metal detectors which consists of two sets of coil which are the transmitter and receiver, a Pulse Inductive MD has only one single coil that serves both function. What happens in the process of operating the equipment is that, the coil sends out pulses of magnetic field deep into the ground. Once it hits a certain metallic object, the magnetic field will reverse its polarity which result into the so called “reflected pulse”.

A “Sampling Circuit” of the PI MD will process the reflected pulses through several stages until it is converted into an audible sound which alert the operator that a metal object has been detected.

Can a Metal Detector Detects Gold?

Many individuals has the wrong impression that metal detectors can only detect pure metallic objects. Most MDs today are actually capable of detecting gold which can be as small as a half grain.

Gold Nugget
Gold Nugget

MDs that are quite good at detecting gold are those with high-operating frequencies such as the Pulse Inductive type of MDs. So the higher the frequency being used, the more sensitive the equipment can pick up tiny pieces of gold. However, the penalty is that it also becomes more highly-sensitive to iron minerals which is bad.

Requirements in Building your first Metal Detector

Assuming that you have the knowledge and skill in building any electronic projects, there are actually a few important requirements that you need to know especially when this is your first time to build your own metal detector.

Here are the following requirements that you need to know:

1. Understand the 3 Major types of Metal Detectors

There are actually three major different types of MDs that you need to understand so that you will know which design you would like to work on.

a. VLF (Very Low Frequency)

– As already stated above, VLF type of MDs operates using two sets of coils. One of the coil functions as the transmitter while the other coil serves as the receiver. The transmitter is the one that sends out the low-frequency of magnetic field deep down the ground. Once it hits a certain metal object, it causes the field to be reflected back up.

The purpose of the receiver coil is to receive any of the reflected field and processed it into an audio tone.

b. PI (Pulse Induction)

– This type of MD has already discussed above.

c. BFO (Beat Frequency Oscillation)

– The most simplest and inexpensive design is the beat frequency oscillation or BFO. It’s due to this reason why these designs are popular for the beginners.

Regarding on how it works, it is actually very similar to the VLF detector because it also uses two separate coils for detection. But that difference is that, its oscillator continuously sends out a frequency signal emitted by one of the coils. If it happens that a certain metallic object has caused interference into the frequency, the second coil will immediately alter the audio tone.

2. Working Schematic Diagram

The internet is a good source for searching various free metal detector schematic diagrams. However, some of them may have errors or they simply don’t work. So if you found a certain MD schematic diagram, it is highly advised that you should conduct a further research about it such as asking those who had already built it successfully.

3. Make sure the Electronic Parts are Available

Some electronic parts especially the transistors and ICs tends to become obsolete where electronic shops no longer sell them. Avoid such designs if you do not know how to find the perfect “substitutes” or “replacements” into those unavailable parts.

Goetech have several lists of metal detector projects that you may want to check. They have frequency-shift detectors, induction balance detectors and pulse induction detectors. I actually built one which is Gary’s PI Metal Detector and its working great.

Electronic Project

Moreover, the advantage of being able to build your own homemade metal detector is that you can keep on improvising it. As you keep on tinkering it, you will be seeing improvement on its performance. But as a warning, building a MD can be very addictive.


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