How to make Metal detector using STM32 MCU.

[parth kothiya]

I want to make metal detector circuit using STM32 for material shorting specification of circuit is given below.

• It can detect ferrous and non ferrous both metal.
• digital out put hi when metal object detected.
• It can show detected piece area.
• It is capable for detecting 1 sq mm metal objects.
• It can also work in vibration environment .
• Programmable store the settings value.

is there any circuit diagram or any ready module I can use it for this project?

[TDK]

Do you have any experience with metal detectors, microcontrollers, or programming?

[parth kothiya]

not with metal detector, but I have experience in STM32 MCU programming & pcb designing.

[TDK]

If these features aren't available on commercial metal detectors, there's probably a good reason for it. The signal you get back is an analog value, not a binary yes/no, from which you need to interpret. It's a very niche area and I doubt there's an expert on the subject here.

There are some resources online which is probably your best best.

https://www.circuitstoday.com/single-chip-metal-detector-circuit

The only STM32-specific feature you have listed is the ability to store values, which you can accomplish using a page of flash to act as EEPROM.

[parth kothiya]

Practically this circuit is not working in industry.

I'm talking about simultaneously multiple frequency detector so for that stm32 need for digital signal processing.​

[thundertronics.com]

A lot depends on application, where metal objects located (food, soil, etc.), is it controlled environment (distance, speed, etc.). You can do some research on internal images of metal detectors (search for "fccid metal detector internal photos") and/or in research papers. Note that it is possible to make a good product even when using simple detector. For example, you can use 1D data from cheap sensor, and accumulate data on a 3D map by using coordinates obtained from accelerometer + odometry algorithm. For controlled environment probably array of cheap sensors may provide good localization, very similar ccd line sensor. For example, an array of compactly spaced sensors perpendicular to movement direction of food production line (contamination detection). Also you might be interested in microwave imaging.

[Danish1]

What frequencies are you talking about?

Stm32 can process audio frequencies quite well, provided you don't have too many channels and the processing isn't too complicated or the way you choose to go about it isn't too inefficient.

And if you want to analyse amplitude / phase from multiple antennas, where external analog circuitry has already converted any RF signals into quasi-static values then there is no time pressure, and stm32 might have enough processing power (although maybe not enough RAM if there are many antennas).

The "stm32" part of this project might be practical. But as a first investigation you might be better off trying things out "in the laboratory" maybe using desktop computing power and display, if only because it makes debugging much easier.

Hope this helps,

Danish