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Encoder Resolution Reader

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Description

Turn a shaft and change the number of encoder bits, and watch the step number, the step size and the reported angle on a dial with a magnified strip that shows single steps. Then solve five problems on step size, steps and degrees, and speed from two readings. Used in Chapter 5.

The dial shows the true angle of the shaft. The rows beside it show what the encoder makes of that angle: the number of steps in one turn, the size of one step, the step number, and the angle the encoder reports, which is the start of that step. The strip under the dial magnifies 3 degrees around the pointer, and each box in it is one encoder step.

Lesson Plan

Grade level: Middle school and up (age 12+). Time: 10 to 15 minutes.

  1. Predict first. A 12-bit encoder has 4096 steps in a turn. Before you move the slider, say how many a 13-bit encoder has, and what that does to the step size.
  2. Explore. Set 8 bits and turn the shaft slowly. The reported angle jumps while the shaft moves smoothly. Now add bits one at a time and watch the boxes in the strip get narrower.
  3. Problems. Five problems in a fixed order. Type the answer in the unit shown and press Check. You get one try for each problem, and 4 of 5 is mastery.
  4. Think about it. A 16-bit encoder has steps 16 times finer than a 12-bit one. Does that make the joint 16 times more accurate?

The 12-bit resolution is the STS3215's 4096 steps per turn, and 16 bits is the listed value for the Damiao DM-J4310. The readings in problems 3 to 5 are illustrative.

Specification

The learning objective, evidence of mastery and content for this MicroSim are specified in Chapter 5: Actuators and Sensors.