Hehe. It almost sounds like the OP is making an improvised explosive device! On Sun, May 16, 2010 at 8:47 AM, Olin Lathrop w= rote: > Art wrote: >> I need suggestions for a low power (or zero power) detector for >> automobiles. It is for a rural site that is wooded, so all vehicles >> must pass along a relatively narrow driveway with lots of trees on >> both sides. So, it is relatively easy to conceal detection hardware. >> Since vehicles are relatively large masses of steel, the thought of a >> magnetic sensor came to mind. As a vehicle drives by the sensor, a >> change in the static magnetic flux is detected. I did some tests in >> my own driveway, and I can see a compass on the edge of the driveway >> move slightly as my John Deere lawn mower is driven past. =A0But, I >> can't figure out how to build something that is practical as anything >> I could build would be relatively high mass and I don't have a clue >> regarding how to get from 'concept' to a practical sensor. > > How about a passive weight sensor? =A0Maybe you can go to Cambodia and st= rip a > few from (yet) unexploded land mines. > > > ******************************************************************** > Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products > (978) 742-9014. =A0Gold level PIC consultants since 2000. > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist