Hi Sean, I don't think that the PIC comparators are the ideal solution here.=A0 Negl= ecting the low resolution (16 steps isn't very precise), the PIC's with the= most comparators still only have 3.=A0 I need 6. Thanks, Brendan >Hi Brendan, > >Why not use a PIC with a built-in comparator or ADC? If you run it >slow enough or allow it to sleep when there is no motion, that should >work very well. > >Sean > > >On Sun, Aug 10, 2008 at 5:16 PM, Brendan Moran wrote: {Quote hidden}>> Hi, >> I'm looking for a solution to monitoring three analog voltages from an accelerometer. =A0I need to be = >>able to set two threshold levels for each voltage. =A0The total power budget for the voltage monitor is >>about 1mA @ 3.3V. =A0I need to set the threshold levels through SPI or I2C. =A0I need to be able to = >>read the voltage levels once a threshold level is tripped. =A0The measurements are outside of the 1mA = >>power budget since they're only for while the system is in motion. >> >> I'm building a position tracking system. =A0I have a sensor which reports a very accurate position = >>delta, but it has two failings: =A0it's power hungry and it's got nasty latency waking up from sleep (as = >>bad as 2 seconds) after waking up from sleep mode. =A0This will be a battery powered sensor = >>package, so power consumption when idle is an issue. >> >> My current solution is to use a MAX1363, which will do both the monitoring and the level reading. = >> I'm limited to 400kbps I2C, which means I have a maximum of 33ksps, divided over 3 channels, = >>not including I2C overhead, which leaves me with about 10ksps per axis. >> >> I think that 10ksps should more than do the job since the tracking system should see movement = >>not exceeding 5Hz, with peak acceleration of no more than 5g (peak should usually be around = >>2.5g) , RMS acceleration closer to 0.5g. =A0The sensor I've picked has four selectable G levels from = >>+/-2.5G to +/-10G which should make that range easy to work with: MMA7261QT. To get = >>position delta, I plan to do a discrete double integral of the acceleration and set a zero point every = >>time that my other sensor reports no motion. >> >> So, is there a better solution for my application than the MAX1363 + MMA7261QT? =A0Together = >>they take 1mA @ 3.3V, which is within my power budget. >> >> Thanks, >> Brendan >> --- http://www.piclist.com/member/annirack-shaw- PIC/PICList FAQ: http://www.piclist.com -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist