Hi Seb, Looks to me that you have understand well that different DC motors will give you different EMF values: http://sirloon.net/loonaweb/sirblog/experimenting-back-emf-motion-feedback <http://sirloon.net/loonaweb/sirblog/experimenting-back-emf-motion-feedback>So, that's it, a poor method using an analog feedback, if you want universal solutions seems to me you have to switch on digital feedback, which as far I know can't be EMF. You can't do it without modifying dividers.
Vasile On Fri, Oct 22, 2010 at 7:57 AM, Sebastien Lelong < [email protected]> wrote: > 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]<jallib%[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.
