Hi All, Seb, What you state is that 10 bits of resolution are required for 5v motors (5mV steps). Is that right? When you create a 25V range, you end up with 25mV steps with 10bits. Is this realy to inaccurate? If I understand correct, back-EMF gives you the voltage proportional to the rotation speed of your motor. If you have a 5V motor at top speed, it will give you (almost) 5V. If you measure in 25mV steps, you get the motor speed in 200 steps (probably 100 steps forward speed and 100 backward). I would expect this measurement is more accurate than the methode itself?
But if you realy do need this accuracy, you could take a 12bit adc and get 6mV steps over the whole range. So this is one way to go. I agree it is probably a bit more expensive, but probably easier and more stable than adding a few resistors, transistors and opamps. But an other way is combining multiple measurements. Your average signal is the motor speed, which changes slow compared to the adc speed. And since your signal is quite noise, you need more samples anyway. And more samples on a noisy signal mean more resolution. Bottom line: you might be solving a problem that does not make any (much) difference in a real life app... Joep -- 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.
