Resolver sensor with stm32

[baksuz]

Hi everyone,

I am just interested did any one ever find a way to connect resolvers outputs directly to microcontroller and was able to sample them.
Resolver has sin and cos negative and positive modulated signal.

Even if that is impossible is there any why with minimal hardware to connect it to microcontroller and do sampling in it, where the output will be a envelope signal of that modulated one.


Thank you for your time     

[capt bullshot]

I didn't do that in that particular way, but why not?

To my knowledge, one can convert resolver output to digital in some ways:
- Resolver to digital style (this is kind of a PLL tracking the speed and position). There are some chips operating this way.
- Synchronously rectifying the output, then sampling the resulting sin / cos tracks like any other encoder that has the typical sin / cos output
- Sampling the resolver signal at the peak voltage.

All of these methods require access to the excitation signal to generate either the synchronous rectifier control or the sampling signal. Depending on the particular resolver and its cable length, one might need some phase shift here.
Typical exictation frequencies are within the 400Hz ... some kHz range, modern MCUs (including the STM32) should have enough computing power to do at least the third mentioned method.
You should provide the excitation reference to a timer input to create the phase shift and ADC trigger, and convert the resolvers output signal to a voltage range suitable to the ADC (one might get away done with some resistors),.
Using the second mentioned method (synchronous rectifiying) provides some more level of noise / disturbance suppression. By providing some oversampling (e.g. about 10 ... 20 samples per excitation frequency period) a MCU should also be able to achieve this.

So my answer is: No, I haven't done that this way yet, but from my experience I'd say it's achieveable.

[jmelson]

Hi everyone,

I am just interested did any one ever find a way to connect resolvers outputs directly to microcontroller and was able to sample them.
Resolver has sin and cos negative and positive modulated signal.

A resolver is a pair of transformers whose magnetic coupling varies with shaft angle.  There is no simple way to read the position.  A very good chip to do it is the Analog Devices AD2S1200, but it is a tad bit expensive.  I make a board that is mostly the reference circuit for that chip, used in motion control applications.

Jon

[Benta]

In principle you can, but it needs damn fast ADCs.
Much easier and cheaper to do an analog demodulation and just read the sin/cos with the ADC.