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dlaing · 07-20-2009, 12:06 PM

dcb,
The motor voltage or Back EMF does relate to the rpm.
Here are some good links.
Back-EMF Motion Feedback
http://www.st.com/stonline/products/...e/an/10775.pdf
The pdf is for 3 phase brushless DC, but has much more detail.

To detect the back emf, we have to wait for the current to drop to zero, otherwise the flyback diode holds the voltage down to Vd. (Figure 5 in 10775.pdf).
But if we space out the voltage reads enough, this is totally viable.

07-20-2009, 12:06 PM	#2045 (permalink)
dlaing EcoModding Lurker Join Date: Aug 2008 Location: Calgary, AB Posts: 21 Corolla bandit - '05 Toyota Corolla CE Thanks: 1 Thanked 1 Time in 1 Post	dcb, The motor voltage or Back EMF does relate to the rpm. Here are some good links. Back-EMF Motion Feedback http://www.st.com/stonline/products/...e/an/10775.pdf The pdf is for 3 phase brushless DC, but has much more detail. To detect the back emf, we have to wait for the current to drop to zero, otherwise the flyback diode holds the voltage down to Vd. (Figure 5 in 10775.pdf). But if we space out the voltage reads enough, this is totally viable.