Reading a motor speed with a resolver

Projects General Guidance
1

hello , i am working on a project that consists on controlling a universal motor with a triac circuit . i managed to control the speed but i have problems with reading the speed with the resolver that came with the motor . i rectified the signal from the resolver and devided the vlotage to a safe range for the arduino with the maximum output being 2.8V . i then used an analog input to measure the DC voltage.
the problem is in the multimeter the output is constant but in the arduino's serial monitor it isn't , it continues to flactuate and not give a constant value .
any ideas why that happens ? and how can i rectify that ?
any help would be great .

2

No :frowning:

Please give a link to the "resolver" datasheet and a circuit diagram how you have it wired to your Arduino (which one?).

3

Try using an analog meter! Any digital multimeter will ALWAYS average pulsing signals.

4

does that mean i wont be able to get a voltage reading with the arduino ?

5

That means you need to average the readings, just like your digital meter averages the readings.

6

Hi, @aboubaker_ouchaib

I think you will find a Resolver is not a tacho generator.
It is a device you supply with an AC signal and read the output of the other two windings.

Can you please post a copy of your circuit, a picture of a hand drawn circuit in jpg, png?
Hand drawn and photographed is perfectly acceptable.
Please include ALL hardware, power supplies, component names and pin labels.

Thanks.. Tom.. :smiley: :+1: :coffee: :australia:

1 Like
7

Please post a link to the product page or data sheet for the "resolver" or the combination.

8

Resolvers read the angular position of the motor shaft, the angular velocity (RPM or radians per second) can be derived from that.

2 Likes
9

My guess is that you won't be able to use analogRead() fast enough to read the outputs of the resolver.

image
image720×520 81.5 KB

1 Like
10

In order to demonstrate how difficult it will be to read the output of the resolver, I have performed the following tests:

Using a function generator, I have been able to create a simulated resolver output.

The following oscilloscope trace is of a 500Hz sinewave, 100% amplitude modulated at a frequency of 40Hz.

The modulation frequency of 40Hz represents a motor revolving at 40 revolutions per second, or 40 x 60 = 2400rpm.

500Hz Signal - 40Hz Modulation
500Hz Signal - 40Hz Modulation800×480 9.28 KB

Using the following code:

  • I have taken 500 samples, as quickly as possible.
  • Stored the samples in an array.
  • displayed the contents of the array on the serial plotter.

int inputPin = A0;
unsigned int sample[500];
unsigned int output = 0;

void setup() {
  Serial.begin(115200);
}

void loop() {

  // take 500 samples as quickly as possible.
  for (int i = 0; i <= 500; i++) {
    sample[i] = analogRead(A0);
  }

  // display the waveform at a leisurely pace.
  for (int i = 0; i <= 500; i++) {
    output = (sample[i]);
    Serial.println(output);
    delay(10);
  }
  delay(1000);
}

Here are the results on the serial plotter:

Screenshot 2024-05-21 2400rpm Resolver.
Screenshot 2024-05-21 2400rpm Resolver.1918×1003 70.7 KB

The problem is analysing that trace from the serial plotter, and coming up with the result of 2400rpm.

I don't know how to do it successfully.

1 Like
11

Step 1: Are you sure that it's a resolver?
Step 2: How are you exciting it?
Step 3: This would be far easier with a resolver to digital converter. I guess that you could reduce the resolver excitation frequency to the point where you could sample it fast enough with Arduino, but that sounds... painful.

1 Like
12

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.