On Fri, Oct 22, 2010 at 10:06 AM, Sebastien Lelong < [email protected]> wrote:
> Hi Vasile, > > 2010/10/22 vasile surducan <[email protected]> > > 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. >> > > Do you mean something like encoded wheels ? bemf is really nice to have > because it's not invasive, you can control any DC motors without modifying > the structure (which is great when hacking RC toys) > > >> You can't do it without modifying dividers. >> > > Is electronic that limited ?? C'mon, there should be a trick ! > Variable gain amplifier. It modifying dividers in software keeping the ADC resolution constant. Still a s**t... :) Vasile > > > Cheers, > Seb > > >> 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]<jallib%[email protected]> >> . >> For more options, visit this group at >> http://groups.google.com/group/jallib?hl=en. >> > > > > -- > Sébastien Lelong > http://www.sirloon.net > http://sirbot.org > > -- > 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.
