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Fuse and E-Stop Power Path

Run the Fuse and E-Stop Power Path MicroSim Fullscreen

You can include this MicroSim on your website using the following iframe:

<iframe src="https://dmccreary.github.io/robot-arm/sims/protected-power-path/main.html"
        height="562px" width="100%" scrolling="no"></iframe>

Description

A 12 V supply, a fuse, an E-stop contact and an arm motor board in series. Predict whether the arm runs, the fuse blows, or the E-stop stops the arm in six situations, watch the current dots stop, then explore your own fuse, load and E-stop settings. Used in Chapter 3.

The fuse blows 0.6 seconds after the current first exceeds its rating. That is a teaching simplification: a real fuse takes longer for a small overload and much less time for a short circuit.

Lesson Plan

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

  1. Predict first. Read the fuse rating, the load and the E-stop state, choose what will happen, and only then watch the dots.
  2. Watch the dots. Current flows only while the E-stop contact is closed and the fuse is whole.
  3. Explore. Raise the load past the fuse rating, then press the E-stop first. The fuse never sees the overload.
  4. Remember. Cutting power makes an arm lose torque, so it can sag under gravity. Chapter 3 covers how to park it first.

The picture is a schematic, drawn with the shared circuit-lib.js helpers. Orange dots show conventional current: they leave the + terminal of the supply, and their speed is proportional to the current.

Specification

The learning objective, evidence of mastery and content for this MicroSim are specified in Chapter 3: Electricity, Power, and Safety Basics.