Converting a Prizm II into a multitone device - any ideas?

[Polymer]

My partner loves her Prizm II and does not want a Prizm V or VI.
That would have solved the problem of multitone in a jiffy.

I've come to see this as a small project to freshen up my rusty electronic skills
and keep my detecting pardner happy...

We have tried a red backlight and amazingly enough even this is blinding,
because we detect in the dark with ambient light only.

I have also come to realize that tonal qualities are extremely important to me whilst detecting.
To me it beats color screens or other so called advancements. Some call them gimmicks.

So I like sounds of the grounds in my ear and my eyes can take care of other things or relax whilst detecting.

Here my technical thoughts on this:

The Prizm II already has an icon display of 8 bits.

My question: how can i simpy convert these 8 bits into say 8 different tones without
getting into complex DSP?

Is there a simple chip on the market that could do this job?

Or could I use an array of 8 different caps/resistors to control a 555 timer to
translate the icon signals into different tones?

I would appreciate your input on this very much.

Thank You!

[Silver Dollar]

It looks to be microprocessor controlled. You'd need access to the program to get the
target data. It's probably locked to prevent copying/altering the code. You could try to
piggyback off the display but it wouldn't be easy as the frequency of a pin tells if it's on
or off. If you open it up and take some pictures we might be able to determine better
what could be done...

[Polymer]

Thank you for your reply Silver Dollar.

Alas, you are right as to the frequency of the lcd control.

I had a look into how static lcd displays work.

They are not as "static" as I thought they would be - like on and off.
The signal reverses polarity at 30 to 90 Hz when switched on.
What a bummer. This is definitely not as simple as I hoped it would be.

I will take photos of the inside. Is there any particular part to focus on specially?

[Silver Dollar]

Just a nice clear photo of the board straight on.

[Polymer]

Just got to find out how to post the picture!

I've reduced the resolution to cut the data load.
Is there a max. picture size on this forum?

If you need the picture in greater resolution, just ask.

Thanks

[satdaveuk]

The most worth while modification on the Prizim range is doing away with the preset threshold on the board and mounting external pot to give option of external threshold instead of just silence missing harder to locate targets.

[Polymer]

Hello satdaveuk,

Thank you for your resonance. I will be changing both pots R58 & R23 to external multiturn ones as specified in the following forum link:
http://www.geotech1.com/forums/showt...13-Part-values

I will be measuring both pots once unsoldered and before twiddling around with them,
just so I have a baseline in case something somehow goes strangely wrong ...

I will post when I've done this, probably by mid next week.

[technos]

I think the only way to get multi-tone out of this is to redo the firmware to msp430 micro in the upper right of Polymer's photo. If there are better pictures of the board, is there someone around that can derive a schematic? It might be worth it on this detector, as the msp430 is a pretty capable mcu.

[Polymer]

Satdaveuk:

It works! I'm thrilled! The value of the installed tiny pot was 920 to 120 Ohms. So not many turns on the new pot to reach the end.
The threshold does become very audible and the detecting distance in air in pinpoint mode is clearly better

Getting the pot externally installed with a knob to fit will be more of a challenge I think. Haven't completed that yet.


technos:

Thank you for you input!
That sounds complex to me and is way beyond my scope .
I am racking my brains to somehow use the 8 icons signalling to get multitone.
If you would like hi-res pics, I will post them.

[Polymer]

Thanks All.

I bought a Prizm V sold as defective and fixed it. My pardner loves the multitone. I would rather spend my time building & perfecting the Baracuda and Nupi pinpointer instead of possibly never figuring this one out.

Technos: You're right. The Prizm V looks the same inside (as the II) and just the firmware is different. Well, the faceplate/display has a few more options...

This topic is closed for me for now.