Lesson 17

Card 2.2: Power, Fuse Sizing, and Electrical Safety

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Format: Calculation workshop

Time: 40 min

Prerequisites: Card 2.1

Core Question

The fuse is the one component we install hoping it dies. How do you size a fuse so it ignores normal operation but sacrifices itself before the wiring does?

Resource (~10 min)

Power: P = VI. A thruster pulling 15 A at 12 V is a 180 W machine; six of them is why our fuse math matters.
The MATE rule: read the fuse and overcurrent protection requirements in the manual, including where the fuse must sit and how its rating relates to measured full-load current.
The stall story: what a jammed thruster draws versus a free-spinning one, and why last season’s fuse events happened.

Activity

Size our actual main fuse: using thruster datasheet currents plus every other load on the SID, compute worst-case realistic draw, apply the manual’s sizing rule, and pick a real fuse value. Then annotate a copy of the SID with your calculation. Compare your answer to what the robot actually ran last year and explain any difference.

Clearing This Card

The annotated SID with shown work, plus a 90-second oral check: “The fuse blows during a mission run. Walk me through what you check, in order, before installing a new one.”

If You Miss This Class

Datasheets and SID copies are in the folder; same artifact and check during studio time.

Why This Matters

The fuse calculation is literally inspected at competition safety review, and the annotated SID becomes real documentation. This card produces a competition artifact, not homework.