Computer Interfacing
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LCD display type

What display would you like to have on the PI metal detector?


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Author Message
Site Admin

Joined: 13 Mar 2007
Posts: 145
Location: Netherlands and Kazakhstan

Feb 06, 2009 1:53 pm

I am currently making decisions about the user interface of the Pulse Induction metal detector. I have decided to use some sort of LCD display, but there are several different types to chose from. The simplest versions are numeric or alphanumeric, but there are also graphic displays which are useful to draw graphs.

In the ideal situation the metal detector has a standard output bus like IC and the display is plugged into that bus. In that case only a software modification is needed to use the new display.

Unfortunately I haven't found the right interface yet. Some displays use IC, other SPI, but there is no real leader in this field. Can anyone recommend which type if display interface I should implement in the metal detector?
New User

Joined: 18 Feb 2009
Posts: 2

Feb 18, 2009 3:02 pm

Don't forget:

we need an audible tone which distinguishes between ferro and non-ferro. While detecting, it is not very practical if you need to take a look at the display all the time.

Anyway, that's my opinion... Wink
Site Admin

Joined: 13 Mar 2007
Posts: 145
Location: Netherlands and Kazakhstan

Feb 21, 2009 1:11 pm

Yes, there will be a speaker. But this is not the largest problem looking at the electronics design. The audible signals can be generated on the fly by the processor as long as the speaker is connected with two lines to a digital or analog output of the DSP. A display is much more demanding and choices in the electronics design cannot easily be reversed once the PCB has been manufactured.
New User

Joined: 03 Mar 2009
Posts: 1

Mar 03, 2009 9:26 pm

The LCD should be on a separate PCB so optionally for simple detectors only audio and some controls is required.
I live in Australia and you are likely to fall down a mineshaft or walk on a snake if you are busy looking at the detector display. Additionally in hot and bright sunlight like we have here LCDs dont do so well.
New User

Joined: 13 Mar 2009
Posts: 2
Location: Gillingham, Kent

Mar 13, 2009 12:45 pm

Both type will be around for some time. SPI devices need address decoding to produce the chip selects, so more difficult if you want to have more than 1 SPI device. I2C uses address decoding from the message itself, so easier to add extra modules or peripherals ono the I2C bus. If you put the LCD connections onto a header, it is possible to get bridge devices from I2C to SPI and vice-versa, so an LCD module change wouldn't be too difficult.

bapak tua

May 10, 2009 11:49 am

I'am new in this group.
In my opinion, based on manu years using metal detectors, in the simple design I need only a audiotone. Two types.
1. A tone starting on a low frequency and rising up at a shorter distance coil<>ground item.
2. The moving methode. A continue tone change in frequency nearer (or moving from) a ground item.
Maybe a simple meter, zeo in midposition and left \|/ right a indication what material. See Puls induction respons graphic.

A more intelligent design with 2 or 3 coils in line, pulsing step by step (1>2>3>1>2 etc).
A small graphic display (like a oscilloscoop)with on the display vertical the emitted ground signal and horizontal the same timebase as used by the coils
can give you information by more ground items.
Maybe it is possible to measure the time between the "switch off" of the coil and the first coming groundsignal. It can be used for measuring the distance item<>coil. I have no idea about that.
Ruud Jansen

Aug 27, 2010 4:59 pm

[b]Design Ideas

1. have bluetooth to LED/LCD display clip to glasses.
2. interface output frequency to voltage driving 7-segment display.
3. isolate display circuit to easily change next version.
4. see if 3rd party display interfaces are around to plug and play user preferences.
5. is there an interface to a cell phone or PDA for display?
6. What of exploring microwave detectors from wireless to use for metal detection?

These are just a few ideas I am tossing to this forum, perhaps there may be a spin off of value as a result.

Aug 27, 2010 5:31 pm

This is not about the display but I don't quite know where to put this comment/question(s).

The field range is to some extent a matter of the strength of the electromagnetic field. What if a fly-back transformer were incorporated into the pulse so the voltages ranged into say, 14,000 volts, would not the electromagnetic field be much stronger and detection of metal accordingly further while lowering the amps so one won't get injured by the voltage?

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