A thermostat for an airconditonar has a mur. switch and will do exactly what the setup below will do. KC7JHO It's not just for radio any more! -----Original Message----- From: Nic van der Walt To: PICLIST@MITVMA.MIT.EDU Date: Thursday, September 25, 1997 12:42 PM Subject: Re: Cheap Accelerometers >> LOUD alarm if anybody tries to "Borrow" it without my permission. It will >> have a small keypad to arm/dis-arm it and must be about the size if a >> ciggarett packet. it will run of a 9V battery. I have most of the keypad >> and I/P O/P code sorted so far it's based on a 16c84. So if anybody has any >> ideas on motion dectection please let me know. It dosent have to be linear >> just digital will do. IE motion /no motion but the sensivtivity must be >> quite good. >> > >Try this: > >Take two concave glas circles. (Used in chem labs, don't know the >fancy name). I used ones about 1" in diamiter. Put a drop or two >of mercury on one and cover it with the other. > >Now you have a conductive liquid runing around in an enclosed space. >Now you slip a couple of dozen contacts inbetween the two edges and >glue everything shut. As this gets bumped and tilted it makes and >breaks contacts like mad. > >I read this with a PC where I could dedicate 32 lines, but there >must be an trick with resistors and A-D's that lets you get away with >less. Or just put in only say 12 wires. Hook them up alternatly to >+ , input , gnd, input. Gives you six I/O's used and probably more >than enough sensitivity. Keep scanning the pins and when it moves >the bitpattern will change. > >Nic >