> For instance, put a 1k > resister in > series with your signal and connect via a 1k and 500E > resistor to two > pins. If the pins input, they don't count. If they are low, > they > reduce the voltage (and thus the resolution for larger > signals).
That's good, too :-) It is not very different from what I wrote, but it saves some resistors and can have a better input resistance. The input resistance here varies, while with my version it stays the same. (not exactly, as the clamping diodes introduce sharp bends to the characteristic) The PIC datasheets i have read recommend to keep the resistor at the analog inputs at 10kOhm or below. I've had another idea: I'm not sure, but you don't look for levels but for changes? So AC coupling trough a capacitor could be a choice. It will subtract the DC part and leave you only with the fluctuations. Might work great if you're controlling voltage, might work not at all if the motor is connected directly to PWM (without an inductor). And there's another, probably the most reliable/exact one: Design your voltage divider for the highest voltage, say 38:10. Then, use three OP-Amps, one unity gain, one with gain=2, one with gain=4. Each is connected to an analog input. R2R-Op-Amps powered by 5V will only swing up to 5V and can therefore not damage your PIC. The input voltage at the OP-Amps is small due to the divider. The divider can have a very high resistance, the outputs have very low resistance. And, I would not call it "voltage normalization", but "Autoranging" ;-) Greets, Kiste -- You received this message because you are subscribed to the Google Groups "jallib" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/jallib?hl=en.
