Surf PI - successful build

[chrisw]

I did all this when I set it up but the resistor is still too hot to keep my finger on it. Maybe it shoudl get hot; it is a 2W resistor so should be able to manage the heat. I checked the pulsewidth again yesterday and it is bang on 120uS. I was just a little worried about this heat buiding up in the sealed box.

[chrisw]

I decided that if a resistor is too hot for my fingers then it is too hot to be sealed in my box.

So now I have replaced the 2W resistor with a 3W ceramic resistor. I could only get this locally if I had a 3.9 ohm instead of 3.3 ohm, but I dont think this would make much difference? Please correct me if im wrong.

Maybe this is a bit of overkill, but it is only mildly warm now, feels much better. The power transistor is lukewarm also. And performance wise I am still getting 19 inches on my £2 coin so I cant tell any difference.

[Sean_Goddard]

A quick note for coil shielding, Try RS nicked spray. it works a treat! Don't forget to leave a small gap in the circle of you will get naff all depth.

THis stuff has 0.7Ohm/cm resistance and makes for a mind blowingly quiet coil on wet sand. You CAN do the top and bottom halves of the coil but you mush be VERY careful that the gaps line up so not to make a shorted turn.

Have fun folks!

[Old cart]

Sean, where do you get that spray?

[Polymer]

A quick note for coil shielding, Try RS nicked spray. it works a treat! Don't forget to leave a small gap in the circle of you will get naff all depth.

THis stuff has 0.7Ohm/cm resistance and makes for a mind blowingly quiet coil on wet sand. You CAN do the top and bottom halves of the coil but you mush be VERY careful that the gaps line up so not to make a shorted turn.

Have fun folks!

WOW!
Although I have no experience in shielding yet, I have been looking into possible solutions finding a myriad of them, dreading the decision of where to begin.
Your experience with nickel shielding appears counterintuitive, because nickel is ferromagnetic and I thought that would be a no-no.
Perhaps the thin layer & low conductivity of nickel, like gold (metal detector wise) mitigates this? Just pondering ...
Anyway, I find this great.

I also found copper based sprays (which are more common) and am wondering if they have the same great effectivity/ease of handling. Have you tried them?

Thank You for sharing this info!

@Old cart: http://uk.rs-online.com/web/p/shield...osols/0568483/

[Old cart]

Thanks Polymer. This may be a little to conductive. Sean, it is quiet but did it affect depth?