Sensor to detect rotation?

Thread Starter

bmbouter

Joined May 29, 2021
75
I'm looking to make a toy that is "rotation interactive". The board the sensor sits on could be oriented in any direction, but I'm only interested in rotation around one axis. I naively thought I could use an accelerometer like the KXTJ3-1057 but it is just an accelerometer and does not also have a gyroscope. If I'm understanding this right the problem is that my signal processing would only work in a orientation and as soon as the orientation changes this won't work.

For example say the z-axis is a normal with respect ot he flat part of the sensory IC, i.e. it's going up/down through the flat part of the IC. I'd like to detect z-axis rotation, that is where the IC is rotating, but the flat side is not flipping end over end (that would be x-axis or y-axis rotation). I'd like to detect that rotation regardless of the actual orientation of the toy.

I'm looking for something very low cost and low power. I don't care a lot about accuracy. It would be nice if it was I2C. What are some sensors I should consider?
 

MisterBill2

Joined Jan 23, 2018
18,176
A static accellerometer will work, that is, one that delivers an output just because of gravity, and reverses the polarity of the output when it is inverted. a potentiometer with a pendulum on the shaft is an example of what I am describing. It responds to gravity.
 

MisterBill2

Joined Jan 23, 2018
18,176
For the very cheapest way to sense rotation about any axis is a potentiometer with a mass hanging at right angles to the shaft.. Those able to rotate almost 360 degrees easily are sometimes available surplus cheap. Even cheaper could be small hobby-class DC motors, which would produce a voltage while in motion. But they will only sense the motion speed not the absolute position.
What has not been mentioned is what the output of the sensor should be. Resistance, voltage, current, or ???. Variable Resistors could be the lowest power sensors of all, since power would only be needed when they were being checked, just a few milliseconds on time.
 
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