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I have gotten the Gary PI to work great and am getting 34 inches detection on a 1 Oz gold coin. this is with the 555 timers. I have built a new version with a PIC micro-controller and have everything working to the last stage where the output is gated by an NTE458 into the last amplifier. I can't get the NTE458 mosfet to trigger with the current circuit layout. Anyone got some suggestions.
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Re: Converting Gary's PI to PIC
Hi Dan
34 inches is an amazing distance! Can you tell us how you construct the coil(parameter)? Are you using one or two coil configuration?
Chris -
Re: Converting Gary's PI to PIC
The coil is 15 inches in diameter, 27 turns of #24 copper wire and copper shielding copper foil tape from some electronic parts house in Arizona that I have lost the catalog for; however, I think it is electronic goldmine (?).
The coil is mounted on a set of radial sticks. I've been asked for a picture of the coil set up and I'll dig out my camera and take a pic.
I also use a meter from Harbor Freight for the meter and no audio output as I am using this in "situations" where I don't want noise and I don't like headphones.Comment
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Re: Converting Gary's PI to PIC
A little additional specs on my PIC problem. The PIC is operating at 5 volts with the same ground level as the 555s however, the 555s are 10 volts. So can someone tell me how to trigger that durned MOSFET. This is driving me battier than usual ..
DGComment
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Re: Converting Gary's PI to PIC
Hi Dan
thanks for the info. I found an image on Garry's web page. Is this your PI unit (see link below)?
Chris
Your unit...??Comment
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Re: Converting Gary's PI to PIC
I come out of the PIC through a MOSFET driver which is opto isolated. That way, on the PIC side it is driven by the PIC pin directly (through a current limiting resistor as you would any LED). On the MOSFET side I switch the higher voltage to the MOSFET gate. This allows you to level shift like you want to do and works to switch the MOSFET very fast. Searching around will find many different flavors of these driver chips.
Good luck,
FJComment
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