simulation problem about metal detector coil

[DJSUOL]

Hi, I am a student who is trying the project of 'Matchless metal locator' and I met some problems while doing the simulation part of the overlapped DD shaped coils. According to pdf, the two coils are working as transmitter and receiver respectfully and at one particular point, the speaker will not scream. When a metal passes, the circuit will warn the people. However, I do not know how to simulate the condition of two overlapped coils in the software since they are not coupling totally as a transformer. Could someone help me solve this problem?

[Qiaozhi]

Hi, I am a student who is trying the project of 'Matchless metal locator' and I met some problems while doing the simulation part of the overlapped DD shaped coils. According to pdf, the two coils are working as transmitter and receiver respectfully and at one particular point, the speaker will not scream. When a metal passes, the circuit will warn the people. However, I do not know how to simulate the condition of two overlapped coils in the software since they are not coupling totally as a transformer. Could someone help me solve this problem?

The balanced coil system is analogous to a loosley-coupled transformer. You simply need to add a coupling coefficient between the two inductors. For example: K1 L1 L2 1m

[DJSUOL]

Thanks for your reply. Do you read the article of 'matchless metal locator'? I am a little confused with the IC1B 'peak detector' part. I think at the critical point that the collector voltage is less than 2/3VCC so the chip output remains high, and when a metal passes the collector voltage is larger than 2/3 Vcc so the 556 chip starts to produce a square wave. Is it right?

[Qiaozhi]

Thanks for your reply. Do you read the article of 'matchless metal locator'? I am a little confused with the IC1B 'peak detector' part. I think at the critical point that the collector voltage is less than 2/3VCC so the chip output remains high, and when a metal passes the collector voltage is larger than 2/3 Vcc so the 556 chip starts to produce a square wave. Is it right?

IC1B is configured as a simple sine-to-square wave converter. The adjustable resistors on the input are there to set the DC threshold level.

[DJSUOL]

however, when I search the working principle of 555 timer, I think it should not output high when the input signal is less than the threshold voltage of IC1B due to the two comparators and RS flipflop, could you please explain it to me?

[Qiaozhi]

however, when I search the working principle of 555 timer, I think it should not output high when the input signal is less than the threshold voltage of IC1B due to the two comparators and RS flipflop, could you please explain it to me?

Have a look at the operation of the 555 timer in either monostable or astable mode. While the capacitor is charging, the output is high. Once it reaches the threshold, the output goes low.

By the way, have you looked at -> Inside the METAL DETECTOR - Second Edition - Published 2015

[DJSUOL]

no. Actually, my project aims to construct a walk-through metal detector model using about 6 same metal detectors to detect different zones and display the metal location. I found the circuit design of matchless metal locator from this forum and I am not sure if it could perform well in my project. Could you please give me some idea for the circuit design?

[Qiaozhi]

no. Actually, my project aims to construct a walk-through metal detector model using about 6 same metal detectors to detect different zones and display the metal location. I found the circuit design of matchless metal locator from this forum and I am not sure if it could perform well in my project. Could you please give me some idea for the circuit design?

I very much doubt that the Matchless design would be suitable for your project. It's a simple minimalist circuit.
Carl gave some information previously on a walk-through design here -> http://www.geotech1.com/forums/showt...569#post149569

[waltr]

no. Actually, my project aims to construct a walk-through metal detector model using about 6 same metal detectors to detect different zones and display the metal location. I found the circuit design of matchless metal locator from this forum and I am not sure if it could perform well in my project. Could you please give me some idea for the circuit design?

I very much doubt that the Matchless design would be suitable for your project. It's a simple minimalist circuit.

Agree that the Matchless is not a good design except as a starting electronics project.

Also, this forum has a TON of great info on all aspects of metal detector design.
Spend TIME searching and READING to learn.
Then Build prototypes to get hands on experience of the merits and down falls of various concepts.

[Qiaozhi]

Hi, I am a student who is trying the project of 'Matchless metal locator' and ...

You should probably go back to your tutor and ask for some guidance. At the moment you're heading off in the wrong direction.

[DJSUOL]

Actually, I just want to build a small size model to achieve the main functions: warning people while detecting the metal and displaying the rough location of the object so I plan to use several metal detectors to divide the whole detecting area to 3 zones. Each metal detector is used to detect the particular zone and the LED or Arduino will be used to display the location. So I am not sure how to be creative for my project since my tutor did not provide much help for me and could you please give some guidance to me?

[Qiaozhi]

Actually, I just want to build a small size model to achieve the main functions: warning people while detecting the metal and displaying the rough location of the object so I plan to use several metal detectors to divide the whole detecting area to 3 zones. Each metal detector is used to detect the particular zone and the LED or Arduino will be used to display the location. So I am not sure how to be creative for my project since my tutor did not provide much help for me and could you please give some guidance to me?

If you use several metal detectors they will interfere with each other. Forget about the Matchless, as it's useless for this application.

You should examine PI designs as a basis for your walkthrough. As your project looks like it's only a proof-of-concept, I suggest using the Arduino to drive the transmitter coil on one side of the arch, and read the outputs of the 3 zones (on the other side) after amplification and integration have been done using analog circuitry. That way you'll have a chance of actually ending up with something that works.

[F117]

Here's a good description of a PI walk-through detector:
http://www.geotech1.com/forums/showt...326#post249326

[DJSUOL]

So your suggestion is to use a PI design to achieve my project. In fact, I think most of the designs in this forum are used for treasure hunting. Do you think it is possible to design a simple PI circuit for this project since I spent some time to learn the matchless to achieve my project for this project and I might not have enough time to learn and test a new type? In addition, I found the continuous wave is used in WT now and do you think it is suitable to design a metal detector based on VLF technology and Arduino?

[Qiaozhi]

So your suggestion is to use a PI design to achieve my project. In fact, I think most of the designs in this forum are used for treasure hunting. Do you think it is possible to design a simple PI circuit for this project since I spent some time to learn the matchless to achieve my project for this project and I might not have enough time to learn and test a new type? In addition, I found the continuous wave is used in WT now and do you think it is suitable to design a metal detector based on VLF technology and Arduino?

If you search the forum, you will see that you're by no means the first student to choose a walkthrough detector for their project. In all instances, the student has left it to the last minute to seek assistance, and has often (as in your case) spent too much time working on an inappropriate design. I suppose that VLF technology could be used to create a walkthrough, but the Matchless design is too simplistic, and drifts over time (as described in the article). Why not pick a simple PI design such as Surf-PI?

Read this link ->
https://kintronics.com/walk-metal-detectors-work/