I am trying to run closed loop V/F control on an induction motor using the TI C2000 TMS320F28069M board. I need to sense the speed in order to develop a speed controller in Code Composer Studio. For that I am using a speed encoder and the eQEP module on the board. Now the speed encoder gives the Ch. A , Ch. B and Index signal in 5V magnitude. However, the F28069 can accept only 3.3V signals.
Does that mean I need to step down the 5.5 V signals coming from the encoder to 3.3V before giving to the eQEP module on the board? If anyone has tried this please do respond. Thank you.
I would use resistors ... ;)
...in a potential divider? Or maybe some 3.3v zeners
2.2k / 3.3k takes 5 down to 3.333.. But also see if the encoder will run at 3.3. A lot of sensors have quite a PS range. G.H. <<<)))
C2000 is a very sensitive DSP controller.
I Suggest using an Opto logic level converter.
please refer to the below link for an example.
these are not optos but Logic-Level MOSFETs which provide bidirectional level shifting as needed for I2C, based on Application Note AN97055 from Philips. Simple and efficient, but imho not needed here.
Yes, you are right, it's not Optos. I am sure this can be used in the application for voltage level conversion.
May be i didn't get your point of view. can you elaborate ??
I would use optos only if I need the isolation barrier. Also, standard optos can be real slow, unless you use fast optos. (The thread starter says nothing about speed.)
In this case here even a simple series resistor would be fine, as long as you respect the maximum clamp current of 2mA of each input. (Well assuming that the power consumption of the MCU is always higher so that there is no risk of "pulling" Vdd up via the clamp diodes!)
Better of course is a real divider as proposed by CustomSarge.
I directly used the 5V supply, seems that I had to connect the shield as well and add a filter at the input of DSP to get cleaner signals. But still do you suggest that I reduce the pulses to 3.3 V ?