What you basicaly say is you want to extend the range and keep the resolution (step size). So you need more bits. You could get an other ADC or tweak an other bit or two. 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). When you do this, keep the input resistance of the adc in mind...
Joep 2010/10/22 Sebastien Lelong <[email protected]>: > Hi guys, hardware guys, > > Years ago, I built a DC motor control board, with back-emf > sensor: http://sirbot.org/sirbot-modules/dc-motor-controller-board/ > This board (and firmware) generates proper PWM signals to control 2 DC > motors, and in the mean time, collect data about produced back-emf voltage, > using ADC. There's no such power control of DC motors (which was actually > done using RC tank transistors themselves), it's just about signaling. > Using this board, there's a warning I'd like to get rid of today. It says > "This board uses ADC (Analog-to-Digital-Conversion) to evaluate motor's > speed. Voltages produced by motors are often far greater than those ADC can > handle. There are voltage dividers on this board which keep those in correct > range. These voltage dividers are designed so voltage produced by motors can > be up to max 12V. If your DC motors produce more than 12V, you'll need to > adjust voltage dividers' values or you will damage this board. You've been > warned !!!" > That is, if I'm using 24V DC motors, voltage coming to ADC will be too great > and could damage the PIC (or worse, I could get wrong data). On the other > side, using 5V DC motors, I'll obtain a narrow spectrum of values, as it's > always divided by 2 (a little more). > How can I perform a voltage normalization ? Whatever the incoming voltage > produced by DC motors, I'd like it to be proportionally mapped to [0,5V]. > I'd like this be dynamic (I don't want to unsolder/solder some resistors > each time I plug a new DC motors). > Please explain to me with very simple words :) > > TIA > Cheers, > Seb > > -- > 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. > -- 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.
