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Treasure Hunting & Metal Detecting Forum Message Boards - Detector Hunter Whites Minelab Tesoro XP > Tech Talk > Metal Detectors > PI Designs & Deepseekers (Moderators: Eugene52, Cornelius) >

Underwater P.I. Project

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silverdog

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	Re: Underwater P.I. Project « Reply #90 on: September 21, 2010, 01:21:02 pm »

Cor

pm sent with payment details

only 3 boards left, I may get some more done but not until after payday Cry

then its 3 weeks approx for delivery - so towards the end of October maybe there will be more

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Paul A

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	Re: Underwater P.I. Project « Reply #91 on: September 21, 2010, 03:51:35 pm »

Hi,
will an irf540a work o.k. instead of the 9640?
Are there any other equivalents if not?

Many thanks!

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GoldDigger1950

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	Re: Underwater P.I. Project « Reply #92 on: September 21, 2010, 05:10:18 pm »

	Quote:	Posted by Paul A
Hi, will an irf540a work o.k. instead of the 9640? Are there any other equivalents if not? Many thanks!

It won't work because the IRF9640 is a P channel mosfet while the IRF540a is an N channel mosfet.

When substituting a mosfet, the internal resistance is critical. The lower the better at the same maximum frequency and voltage. For audio applications like this, the effect is usually (emphasize that word) not critical. The other factors are the amount of current required to turn it on or off and the peak voltage it will be switching. In this case, 200v maximum. The 555 timer is fairly robust so the number of substitutes would be large for this circuit but maybe not for others. Does that make it fairly clear?

To sum it up, in an audio circuit like this one, probably any P channel with a low internal resistance, the proper operating frequency and proper maximum voltage will work. For a radio frequency circuit, a very special selection way beyond the scope of this forum would be needed.

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	Re: Underwater P.I. Project « Reply #93 on: September 22, 2010, 12:56:23 am »

Thanks GD,
I just spotted that a little while after I'd posted .
For some bizarre reason the 9640 is a bit hard to get hold of here...
Great info.... thanks!

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	Re: Underwater P.I. Project « Reply #94 on: September 22, 2010, 03:07:54 am »

Most of the parts you will get in

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silverdog

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	Re: Underwater P.I. Project « Reply #95 on: September 23, 2010, 02:47:22 am »

Sorry Guys

All longboards have gone,

I will get some more done soon, watch this space

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	Re: Underwater P.I. Project « Reply #96 on: September 23, 2010, 02:50:21 am »

	Quote:	Posted by silverdog
Sorry Guys All longboards have gone, I will get some more done soon, watch this space Silverdog

Coincidentally, mine came in the mail today! Thanks, mate! You're aces in my book. These are lovely boards. The DIY types here would be crazy to pass them up.

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	Re: Underwater P.I. Project « Reply #97 on: September 23, 2010, 05:24:37 am »

I can't download it yet!
I can't download it!
I want it now! But I can't download the files yet! I don't have 5 posts!

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	Re: Underwater P.I. Project « Reply #98 on: September 23, 2010, 11:22:22 am »

You have six post as of this one! Funny

I have a original Surf PI Coil to us on this one.

Whooooo Hoooo! Great

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Paul A

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	Re: Underwater P.I. Project « Reply #99 on: September 27, 2010, 03:02:48 am »

Finished mine yesterday!
A had a coil off an old "autopulse1" P.I. detector (9") so decided to try it....
Works perfectly!!! Cheesy

Don't know how many turns of wire it is but it measures out at 235uH if that helps!

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