Surf Pro Kit

[dime196604]

I am very new to this hobby, haven't even stated as of yet. I have a surf pro kit i bought off ebay. It is the same kit in this video https://youtu.be/LO6XYJ6td3U this is not my video. Just the same kit i have.I have the board all put together and have tested that it works with a simple mono coil. I am just looking to see if there is any improvements anyone knows for this board. Also, what would be a good coil to build and start with? I have no experience with metal detectors as of yet. I have been a amature radio operator for three years now, so i have built a lot of electronic kits and such, like small radio and amplifiers. So i do have some background in working on electronics. I figured the best way to start this hobby was to start building, and am looking forward to any info and help you guys have for me.


Thanks,
Dustin

[dime196604]

I also don't think I fully under stand shielding the coil. Do you shield it and run the shield the board ground? Or do not connect the shield to ground?

[dime196604]

Anybody out there???????????
Now i am looking into adjusting the damping resistor. I have a scope but only one channel works. Is it possible to set the damping resistor with only one channel? If so how would i go about it? Also how would i go about setting it without a scope?I have read about doing it with a scope here on the forum, but none of them say how to do it with any detail.From reading on this forum i believe i have the Surf XX board. Anyone willing to help me with this?

[Koala]

Anybody out there???????????
Now i am looking into adjusting the damping resistor. I have a scope but only one channel works. Is it possible to set the damping resistor with only one channel? If so how would i go about it? Also how would i go about setting it without a scope?I have read about doing it with a scope here on the forum, but none of them say how to do it with any detail.From reading on this forum i believe i have the Surf XX board. Anyone willing to help me with this?

9.5" 230uH is a good starting place. Not too critical what wire you use. Use the coil calculator sticky in the coil section of the forum

[Qiaozhi]

Anybody out there???????????
Now i am looking into adjusting the damping resistor. I have a scope but only one channel works. Is it possible to set the damping resistor with only one channel? If so how would i go about it? Also how would i go about setting it without a scope?I have read about doing it with a scope here on the forum, but none of them say how to do it with any detail.From reading on this forum i believe i have the Surf XX board. Anyone willing to help me with this?

Use an adjustable damping resistor tool:
10k pot in series with a 200R resistor, and a 2k resistor in parallel with both the pot and resistor. This will give you an adjustment range from 181R to 1672R.
Attach the one good channel of your oscilloscope to the output of the preamp, and adjust the pot until you achieve critical damping. Disconnect the adjustment tool and measure the final resistance. Replace with a fixed resistor that has the closest value.

[FatBob]

Here's some pictures of a coil with different resistors. You want limited rise after the pulse.

Damping.zip

[dime196604]

Thanks for the reply guys. I have a LC meter so I don't have to use the coil calculator. When adjusting the damping resistor, do I need to be detecting metal? Or do I just need power going to the coil? Also what kind of waveform would I be looking for? I have seem a few examples here on the forum, but I am not sure what waveforms are the ones I'm looking for. Again, thanks for the replies.

[dime196604]

Fatbob, what one of those four examples would be the waveform I'm looking for? I'm not very experienced with a scope. The only thing I have used my old analog scope for is adjusting modulation on my AM transmitters. so I am used to only look for a smooth wave.

[FatBob]

I would say the 400 ohm is the best. It is narrowest and does not rise going to the level part.

[dime196604]

Thanks, do i need to be detecting anything when adjusting the damping? Or just have the coil connected with the power on? Sorry about my grammar on the last post, i did it on my phone and not the computer. Can't see the whole post when doing it on my phone

[Koala]

Thanks, do i need to be detecting anything when adjusting the damping? Or just have the coil connected with the power on? Sorry about my grammar on the last post, i did it on my phone and not the computer. Can't see the whole post when doing it on my phone

No

Just power.

[dime196604]

That's what i needed to know for now. Thanks. I was try and post pics of the wave i get on my scope, so you guys can let me know if i am moving in the right direction.

[dime196604]

May be a dumb question but what chip on the board is the preamp? I'm used to working on radios and old tube gear.

[FatBob]

The preamp is the first opamp the signal hits as it enters the board;

[dime196604]

The preamp is the first opamp the signal hits as it enters the board;

[ATTACH]36602[/ATTACH]

Thanks Bob