Surf PI 1.2 Problem

[Marauder]

Hi Guys,

I'm a little stumped on the surf PI that i've just built. Its making a very quiet buzzing noise, and seems to be only just able to detect metal. I'm using a 12v battery that generally reads about 12.7.

Any good tutorials on how its supposed to work? or trouble shooting blogs?

volume is very low, and the only way to hear it is to crank up{(or down) the sensitivity.

Any help would be great.

Thanks

James

[Marauder]

Had a bit more of a play with it, and it is detecting metal but very insensitive.

Maybe the coil is not good? It's 12 inch nuggeteer.

Any thoughts?

[Thomas]

what is the inductance on the coil?

[soverey]

Had a bit more of a play with it, and it is detecting metal but very insensitive.

Maybe the coil is not good? It's 12 inch nuggeteer.

Any thoughts?

You have to tune the damping resistor for every specific coil, in order to obtain critical damping. You have to use a variable 2 w resistor. I think Carl posted a schematic for finding the right value for the damping resistor, search the forum.

[Marauder]

Thanks guys! I'll have a look for carls thread

[kt315]

or trouble shooting blogs?
---
just trouble shooting copy http://www.geotech1.com/forums/forum...Published-2015

[Marauder]

Looks like that would be good book.

So I'm guessing that R6 is the damping resistor for the surf pi. What's the inductance of the coil that kit is built for? If you're going to but in a variable damping resistor in would you do it in the place of r6?

[soverey]

Yes R6 is the damping resistor , you will replace R6 with a damping resistor adjustment tool : The damping resistor tool consists of a 10k pot in series with a 200 ohm resistor, and both in parallel with a 2k resistor. After adjustment, measure the resistance of the network and replace it with a fixed resistor of the same value. Use 2 w resistors for the adjusting tool and also for the final fixed value damping resistor. If you don't have access to oscilloscope, adjust the variable resistor until you get best detection.

[Marauder]

Hi soverey,
Thanks for info re damping resistor. Did make a little bit of difference, but still unable to register large coins at all. Can pick up a pair of pliers and a drill,but I think that maybe the sound isn't working properly as it is very quiet, like a whisper.

Any thoughts?

[Rayjay]

Check the offset voltage at TP2 (set for 0.0 Volts). You might also want to check the parts list and location of components just to make sure all parts are in the correct location. Finally, check solder connections. Just a thought.... Good luck

[junkhunter]

i spent a lot of time downloading peoples circuit board pics that worked from many web sites before i built mine i bet you have put something in the wrong place mine fired up first time





check my pics out in my profile has build pics this is fully under water unit and ear phones .pm me if you need any help guys

[nathmurr]

I've just built mine and got to say it works pretty damn well, built a pinpointer for it which works great too. this might not apply to you but I built it inside an aluminium box and grounded the box. I had a similar issue, mine worked well on the bench then in the box it had rubbish sensitivity. I found the cause was because I had routed one of the PCBcoil wires close to the box wall and it was interacting with the grounded box. I imagine if you route a coil wire close to the 0V wire or something you may get a similar problem, try spacing out the coil wires as much as possible when testing and don't put them too near the supply wires. Once I moved the wire away from the box wall I had great sensitivity.