Hi Seb,
You write: > When a motor @12V runs at its max speed, it can produce back-emf up > to (almost) 12V. When it's not running, well, that's 0V... The voltage > divider I'm using make this 0-12V range fits into 0-5V. Did you take into account that your motor can run forward and backward? If you do not swicht the back-emf circuit, you will get -12...12V. Seems you're going into a lot of hassle and I am not sure why. You qualify your needs as: > When powered @5V, I loose a lot of resolution, thus information. Even more > when such a voltage divider would be designed for power supply up to 24V... You do loose resolution of your adc, but how does this affect your goals (which is determine the speed of your motor). In my experience, back-emf is not a very accurate way to determine the motor speed, so 10 bits over +/-24V might be overdone already. And in addition to this, you can take more samples to increase resolution of your measurement. You probably will have to do so anyway since the signal is noisy (which helps in getting a higher resolution). Bottom line: see if there is a problem with the straight-forward approach before you start fixing ;) Joep PS the accuracy probably depends on motor quality and voltage, so you might take that into account when you do some tests. And if you want to know the speed, get motors with encoders, e.g. the faulhaber ones from Voti... -- 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.
