Hi,
I am trying to measure the velocity of a voice coil actuator by using back EMF.The coil is controlled using a PWM scheme. The conventional method of sensing is to stop the current going into the coil by switching off a transistor, and wait for the energy to dissipate through a flyback diode or some sort of snubber circuit, then measure the back EMF. However, for my application, I can't wait for the energy to dissipate because it takes too long. My question is, can I just put a resistor in series with the flyback diode then measure its voltage drop after a fixed time after switching off the transistor to infer the velocity? The voltage drop across the resistor should be a function of the initial current through the coil, which is fixed, and the back EMF of the actuator, correct? Essentially my reasoning is that if the actuator is moving fast through a magnetic field, the energy stored inside the coil will be dissipated faster.
Does this make sense to anyone? Thanks
I am trying to measure the velocity of a voice coil actuator by using back EMF.The coil is controlled using a PWM scheme. The conventional method of sensing is to stop the current going into the coil by switching off a transistor, and wait for the energy to dissipate through a flyback diode or some sort of snubber circuit, then measure the back EMF. However, for my application, I can't wait for the energy to dissipate because it takes too long. My question is, can I just put a resistor in series with the flyback diode then measure its voltage drop after a fixed time after switching off the transistor to infer the velocity? The voltage drop across the resistor should be a function of the initial current through the coil, which is fixed, and the back EMF of the actuator, correct? Essentially my reasoning is that if the actuator is moving fast through a magnetic field, the energy stored inside the coil will be dissipated faster.
Does this make sense to anyone? Thanks