Hi! IMHO overvoltage protection with diodes is a good choise for this application. (It shouldn't be necessary to compensted the diodes impedance in this case.)
But Zener diodes with 1.8 V are expensive and not so easy to find. Instead, I use a voltage divider and a normal LED (orange color) in parallel to the ADC input. The LED current is nearly zero below 1.5 V and grows to maximum at 1.8 V. That way I loose 1 / 6 of the ADC resolution. But it's a cheap solution with low space requirements on the PCB. And it provides an additional overvoltage indicator (the burning LED). When I need high accuracy (or full 12 bit range), I compensate the non-linear LED current by software. The maximum overvoltage can get adjusted by the impedancy of the voltage divider. (It isn't limited as in the OP amps solution.) BR -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
