Surf PI - successful build

[chrisw]

Hi Guys,
I have been following all these posts about the surf PI kit for months now and you all inspired me to have a go. So I bought a kit off the internet and built it. It all works great, and all the information about coil building was really helpful. I seem to have good depth now. I also made a vid on youtube. Just a matter now of making a shaft and fixing the box on. So thanks to everyone on this wonderful site.
http://youtu.be/LO6XYJ6td3U

[6666]

CHRISW, which kit did you buy ?

and yes, if you could make another video or give any info on your coil mods would be very helpfull thanks.

[Qiaozhi]

chrisw - I have moved your post to a new thread to avoid the bickering that has started between a couple of members.
Please do post the details of your "super" coil. I'm sure many others will find this of interest.

I assume you're from Birmingham?

[zelkos]

Well done chrisw.
Nice video, and an interesting coil...
Kit is a direct copy of SurfXX PCB which is in this topic. 50$ + shipping - a bit much overrated... ->
http://www.ebay.com/itm/SM-PRO-PI-ME...item35ddcb26f7

[chrisw]

I bought the kit of ebay from Tacoma56, I saw him mentioned on one of the threads. £30. Shipping cost £19 though, bit expensive, but it was a good kit.

And yes, I was born in B'Ham, but live about 20 miles north of B'ham, little town called Cannock.

[Qiaozhi]

I bought the kit of ebay from Tacoma56, I saw him mentioned on one of the threads. £30. Shipping cost £19 though, bit expensive, but it was a good kit.

And yes, I was born in B'Ham, but live about 20 miles north of B'ham, little town called Cannock.

Hint: you can also get kits from silverdog for a cheaper price -> www.silverdog.co.uk

It was the Brummie accent that gave it away.

[godigit1]

Nice job on the build and the coils. I bought the same kit and it performs vary well I think. I also have the hammer head Rev d Vco opt And straight out of the box with Carls cal settings and no mods yet. Both perform very close with only a slight edge going to the hammerhead as it seems to handles Emi better. You appear to be in a pretty quite enviroment, Or do you have the machine cranked way down for the indoors? I dropped R34 down to R100 It helped a little with the volume. I have a 4 inch coil operating at 8us (If Im measuring right) it has good sensativity and depth. Please do post your mod for the coils when you can.
What kind of sensativity to very small targets are you getting from your spiral coil? Say something like a 1/2 gram lead chunk or gold stud earring.
Have you been able to scope your fly back yet? The reason I ask is Mine seems to be inverted??? Im wondering if this is specific to the kit or I messed Up!
Mine spikes down at 250 volts. Must be inverted somehow. Seems to work fine though.

Thanks for the video and good luck with the rest of your build!

[chrisw]

I did look on silverdogs website first, but I wanted the square board rather than the long thin one. Also I wanted the for pot one. I couldnt seem to find that. I will try to tone the accent down a bit ha.

[chrisw]

I havent tried it with very small targets, just my wifes small gold ring. On the spiral coil the depth for the ring wasnt too good but it was good with coins. But the problems I had with the spiral coil was it picked up my hands so I thought it would be too much trouble trying to shield it. So I have concentrated more on the mono coils, then my latest basket coil. I have got an old scope, but I dont know any test points to connect to. I did connect it to a few places but couldnt get the nice square waveforms everyone else shows. All my waves looked a mess.

[6666]

I bought the kit of ebay from Tacoma56, I saw him mentioned on one of the threads. £30. Shipping cost £19 though, bit expensive, but it was a good kit.

And yes, I was born in B'Ham, but live about 20 miles north of B'ham, little town called Cannock.

Thanks, its good to know what people are building and what works, looking for your new video.

[godigit1]

You can set you damping resistor from pin 6 of the 5534 and Ive been looking at the flyback on the input side of R6. Im not sure why it is inverted yet.

Scope is set at 5us, 5 volts top trace, 5vx10 bottom trace.
Post #5 in this thread has some good info as well for set up and tuning.
http://www.geotech1.com/forums/showt...uda-and-SurfPI
Hope that helps with the mess..

[Qiaozhi]

You can set you damping resistor from pin 6 of the 5534 and Ive been looking at the flyback on the input side of R6. Im not sure why it is inverted yet.
[ATTACH]31673[/ATTACH]
Scope is set at 5us, 5 volts top trace, 5vx10 bottom trace.
Post #5 in this thread has some good info as well for set up and tuning.
http://www.geotech1.com/forums/showt...uda-and-SurfPI
Hope that helps with the mess..

Looking at the scope image, I don't think the signal is inverted. I believe you've mistaken the overshoot as the inverted signal. The top trace (preamp output) starts off following the lower trace (TX) until the opamp rails out. Once it comes out of saturation, the signal again starts to follow the lower trace, but overshoots slightly due to being underdamped, and then settles at 0V. If the value of the damping resistor is reduced, you will see the overshoot decrease in amplitude, and the two signals will match (except for the point where the opamp is saturated).

[chrisw]

Thanks for the test point godigit1, I put my scope on this but I couldnt keep the trace still. But the scope has been in the attic for 30 years so it probably duff. But I could catch a glipse of the waveform, and it seemed to look ok.

New video about my coils is now on youtube. http://youtu.be/bIGa3vhjd5I

[zelkos]

Hi Chris,

I'm not sure, but I think you're wrong...
For now, you're trying to find the optimal coil for your circuit.
Different coils have different resistance and inductance. Every time you change the coil, you should adjust R6 to get optimal performance. R6 is a damping resistor - 2W. Of course, for that you must have a working oscilloscope.
After adjustment you can compare coils, and see which is better.

By the way, how many notches is on base of your bigger basket coils at the outer edge?

I have a spiral coil as you, and this coil "sees" only my left hand, because I have a wedding ring ...

[chrisw]

Hi, Yes I know r6 should be adjusted, but not been able to check prevents this. So for now I just have to leave this and experiment with things I can change. The bigger basket coil has the same amount of notches; I just scaled it up a little, I dont know if it will be any better or even work, but it gives me something to try.

I understand what you say about the hand test, mine was always being detected until I removed my watch haha.