Help Spider web coil

Look here!   Gary has done them and they work quite well.  He even sells them ready made at a good price.

I know what your talking about.   It looks like a old time Am Radio antenna.   Inter woven over an cut form.

He has one in the site some place.   Can't find it.

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Posted on: August 01, 2011, 08:35:16 PM

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Because of the way there Wound, the C is quite low.

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Basically, it is one terrific receiver antenna and a not-so-hot transmitter antenna. Your success is based on using a high amount of power for transmitting and it being very sensitive as a receiver antenna. You have something in your favor though. Since the same antenna is being used as both, the orientation of the fields is perfect making it the best kind of match possible.

A way to improve your system might be to increase the field in the vertical orientation by making a separate transmitter antenna that would fit inside of the receiver antenna. To protect the receiver circuitry, you'd need to switch the receiver signal off when the transmitter was doing its thing. The deeper you can get the transmitter signal, the better your target's inductive pulse will look to the receiver giving you far greater depth and even smaller target recognition. This is where a PIC chip would be handy to control all the timing.

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Your inductance will be the same for both coils since the circuit was designed to that impedance. Look into using a solid state switch for turning off the input to the receiver when the transmitter is on full power from a pulse. This will prevent the receiver from literally blowing up. The high voltage spike induced into the receiver coil could burn out the diodes and pump straight into the first stage of amplification. Just tap off the pulse control for the transmitter and open the input to the receiver prior to the diodes while the transmitter is working. The solid state switch should be a small part but select a high voltage device. Current will be miniscule but the voltage spike will be very high.

Remember that the transmitter pulse will be felt in both the metal objects in the ground and the nearby receiver coil. Yes, mucking around is expensive. Just have a look one day in my reject box of circuits that went from the drawing board to prototype and failed. I keep them all, along with documentation, just to make sure I don't do the same thing twice.

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		Quote:			Posted by xavier
	Great thanks GD now that I have some weapons I will attack the problem. I really think that this will be a fun project can't wait to get started so if I go MIA you know where to find me LOL

Over here they say you are "elbows out and bum in the air" which is a perfect description for a man hard at work on a problem.

Above all, enjoy yourself. When you have a worthwhile project for a PIC, it is much more fun than making LEDs blink.

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I absolutely know that joy all right. Yesterday, I was working on a program to communicate between two PIC devices using a WiFi USB device. That part works perfectly with full handshaking. The bit I am working on is not troublesome but tedious. I'm building a parser (human language interface) for the computer side of things which can be translated by the PIC system. I have to build the interpreter into the device so it can control up to 255 functions such as switching, motor control, lights and sense a variety of inputs too. Full reporting of system status is also required. All quite easy to do but the parser cannot make a mistake or there could be fatal (not in human terms - in machine terms) consequences if a command is missed or misinterpreted.

The tediousness of testing requires me to enter words into the parser that would not normally be sent to it. I am using a full dictionary of 300,000 words to test it automatically and recording the results. Like I said, tedium to the max. Necessary, though. The parser is able to parse up to 4 commands in a string. A string of "switch tk01 full throttle" would be a typical command. The word "fully" cannot be used but unless you train the parser, it could be accidentally send and interpreted. I'm sure you get the idea.

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