AVR+DSS Frequency Mod SD2100V2

[mario]

Thanks Mario and Mick. Going to try one of the function generator modules at first. If that doesn't work too well I'll build your project (I'm a lazy guy). Just picked up Carl's book, maybe I'll learn a few things. It's forums like Geotech and guys like yourselves that make this hobby interesting and successful. Much appreciated.

Always glad to help,

Good luck

[Mechanic]

G'day Mario,

Good to see your still kicking around!

Now, square waves or sine waves..... It matters not. As long as it is stable. The sine waves from the oscillator are converted to square waves before feeding the clock signal to the 4040. I have actually built a "vco" type cct with 10 coarse frequency settings from 1 to 4 mhz and a fine tune for tuning out emi. It all fits on a board 36mm X 18mm. The output is extremely stable with only a small amount of slow frequency drift due to temperature. It uses 29 components and the output is a square wave.

Cheers Mick

[mario]

G'day Mario,

Good to see your still kicking around!

Now, square waves or sine waves..... It matters not. As long as it is stable. The sine waves from the oscillator are converted to square waves before feeding the clock signal to the 4040. I have actually built a "vco" type cct with 10 coarse frequency settings from 1 to 4 mhz and a fine tune for tuning out emi. It all fits on a board 36mm X 18mm. The output is extremely stable with only a small amount of slow frequency drift due to temperature. It uses 29 components and the output is a square wave.

Cheers Mick

Yeah, it's been years.

After my machine broke, I kind of got bummed out and stopped my minelab projects. Around that time, I also moved to a new house, so I replaced those projects with remodeling work.

So yeah, I've been busy, but still feeling bad about my old SD2100...

[jtz54]

Is your 2100 still broken? I fixed my friend's GP Extreme with the help of Woody and the guys at Detectormods forum. It's hard when you don't have a schematic and everything is covered with paint.

[mario]

Is your 2100 still broken? I fixed my friend's GP Extreme with the help of Woody and the guys at Detectormods forum. It's hard when you don't have a schematic and everything is covered with paint.

Yeah, it's still broken.

With everything else done, I'll probably try to get it working again one of these days. It's been hunting me.

[jtz54]

If you check the detector mods forum and look forGP extreme broken parts, there is a lot of info on common failures and replacement parts. Considering your level of expertise should be fairly easy for. Good luck and thanks for your efforts in this forum.

[Finderskeepers]

Hi all,

I'm in the process of drawing the circuit board of this project, but I presume that the sinusoidal out terminal and ground terminal is connected in lieu of the crystal on the sd2000 board.
Just want to verify this is correct.
When its complete and working, I intend to publish pcb artwork for a doublesided holethru version for this forum.

thanks and regards

Martin

[IBGold]

Correct mine using Mario's board has been running faultlessly for at least two years now thanks to Mario's skills.

Regards, Ian.

[Finderskeepers]

Thanks for that Ian, this must be the ultimate mod for the 2000/2100's. I hope to get it working by next weekend. Got the board etched today and soldered the vias. Still waiting for parts to arrive, was unable to order the 100mhz crystal so i got a 50mhz instead. I noticed in an earlier post that it should run ok with a 30mhz crystal.

[IBGold]

Yes with this Mod and cleaning up the +5V/-5V powersupply and improving the DC filtering of the IC's makes a big difference although my unit has been radically modified I am very attached to my old girl would not get rid of it for anything even though it only gets used intermitantly these days.

Regards, Ian.

[mario]

Hi Ian, good to see you're ok.

Stateside, these detectors are increasingly being used for meteorites because they go deep. I found some nice gems back in the day and have thought about making them into jewelry. But I hear some are radioactive though, so maybe I shoudln't ... the thought of giving someone a bad case of melanoma is not my idea of a good gift...

I got your message, Finders.

Oscillator speed does matter in terms of signal integrity, so I would still look for a 100Mhz Oscillator. I experimented with 30 Mhz before settling on 100Mhz and noticed some drift. You could modify the Hex easily to change the multiplyer, but why do so considering the drift issue?

I still have boards (and parts) left, so you could have ordered them from me. I thought $15 for the board was reasonable considering the amount of time I spent on the project.

I thought this project was dead, so it's nice to see that there's still interest. Maybe I should post it on my google account to increase availability now that geotech has gone private?

Can you post some pictures?

[Finderskeepers]

Hi Mario

Those 100mhz are hard to find, but last night I hopped onto Element 14 which had 26 left in stock and ordered two. Should receive them later next week. Got my unit working, but it should work properly when I get that crystal replaced. I built this signal generator so it would operate at lower frequencies and now I have a substantial increase in detection depth.
This detector does not operated well in the suburbs, so to test it properly I will have to go out of the city.
I hate working with smd parts but I am happy that the ad9851 mounted well. I have posted a few photos of my unit.

[Jiminy]

Mario, ever get your detector working? Remember back a while ago that it quit.

Haven't heard or seen much of you over the past year.

Hopefully you and yours are all doing well.

[mario]

Hi Mario

Those 100mhz are hard to find, but last night I hopped onto Element 14 which had 26 left in stock and ordered two. Should receive them later next week. Got my unit working, but it should work properly when I get that crystal replaced. I built this signal generator so it would operate at lower frequencies and now I have a substantial increase in detection depth.
This detector does not operated well in the suburbs, so to test it properly I will have to go out of the city.
I hate working with smd parts but I am happy that the ad9851 mounted well. I have posted a few photos of my unit.
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Glad to hear it working.

I intentionally used smd parts to keep the board small. Also, you'll be surprised at the number of parts manufacturers keep from DIP packaging. Even SMD is becoming increasingly rare these days, with some companies preferring others like QFN (yikes!).

Once, you get that 100Mhz Osc, you should access the full range of frequencies intended for your SD2000.

Mario, ever get your detector working? Remember back a while ago that it quit.

Haven't heard or seen much of you over the past year.

Hopefully you and yours are all doing well.

Oh I'm still in the modding seen, just modding different equipment.

You could check some of my public stuff at thingiverse.

Shortly after frying my metal detector, we bought an old house.

Needless to say, I needed new toys to make the much needed repairs.

So, in other words, I find myself these days spending more time with my router table and miter saw than my metal detector, which I never did fix (One thing lead to another, and I found myself caught up on my woodworking hobby. So out of sight out of mind for my poor SD2100).

Like I said before, it's still always good to see some interest in this project. I'm glad people were able to benefit from it, even if there were only few.

[Finderskeepers]

Got the 100mhz crystals today and popped it in my dds unit. It now works fantastic, the machine operates right down to 1.1mhz with no problem. I just love how you can fine tune it and find a stable frequency. Nice work Mario. Will put a short video on youtube soon.