On 10/1/06, Wouter van Ooijen wrote: > > What happens if a PIC pin configured as a 10bit a\d receives negative > > voltage... > > then you are operating the PIC outside its specifications. anything > might happen, including cold fusion. Wow, some of my colleagues would be extremely happy ! :) One fact about could fusion which was demonstrated is the experimentator could influence the experiment just with his believe... > > > I'm interfacing an lm35c temperature sensor to a > > pic and it says > > on the datasheet that lm35 will produce a negative output > > voltage when > > measuring less than 0 degrees celsius... > > it won't 'produce' a negative output. the trick is to have the gnd of > the lm35 1..2 volt above the PIC ground. read the lm35 datasheet, it is > explained there. > Let say only from the beauty of this topic that indeed will produce voltage somewhere between -0.5V...+4.5V range. In this situation you'll supply the PIC at 0...+5V, tie the -Vref at -0.5 V and +Vref at +4.5V. All negative voltages connected to PIC must use limiting resistors (220ohn to 1K). Then the input voltage may swing between -Vref to +Vref. The trick used here is that protective diode voltage drop inside PIC is not 0.3V as datasheet say but around 0.5-0.6V when indeed there is current flow through those diodes. Vasile -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist