Let's Make Robots!

Inductive Guidance

       I am trying to build a robot lawnmower(yes another guy trying this).. I need to understand Inductive guidance or RF technology a bit better to build a buried wire circuit for this.. I have read alot on the web and am starting to understand inductor/capacitor circuits.. I built a transmitter using a 555 and a 2n2222 to raise the current in the wire.. I then built a L/C circuit with a 339 comparator and I can tune it to pick up the signal from the wire(I can see this on my oscilliscope)..

        My question is that I seem to have alot of noise as well and even if I touch the inductor I see alot of noise from that as well.. Is there an electronic way to filter this out? Did I make my circuit wrong? Is there a better way to accomplish what I am trying??(maybe using am radio signal in the wire instead of RF)??  Please any information on this topic would be greatly appreciated as I have invested ALOT of time and money trying to solve this issue..

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   Here is the main link..


For the schematics click on diary on the front page then scroll down to the midway point .... It is not so much a schematic as a concept drawing though..

In looking at the schematic and reading his description, it is not RF, it's 38kc. So, basically, it's still an inductive loop design with a range of only 50cm.

   I thought you told me that for it to be an inductive loop it would have to have multiple turns?? Now I am confused..Does it have to be a certain frequency to be RF?

I said the more turns you have, the stronger the field and the better the signal to noise ratio.

Normally, anything over 100kc is considered RF, though at that frequency the circuitry looks more like audio than RF.

    First of all what do you think of that circuit/system? Will it work properly (in your opinion)?

    Oh ok.. that makes sense... So if it is running at 38khz and I were to use your other suggestion about multicolor wire that would increase the signal strength right?

    I presume the capacitors that he has marked with an * are the same value, and I can calculate the values from an online L\C calculator correct?

   One other thing can the signal strength on this circuit be increased by any other means? (ie incease voltage or current in buried wire)