Electronics basics and bench safety

Robotics electronics can be taught without formal circuit theory, but not without a working mental model. This is the smallest model that survives contact with a real robot.

The three quantities

• Voltage is the push. Set by the battery, and mostly your choice at design time.
• Current is the flow. Decided by what the circuit is doing: a motor under load draws more than the same motor spinning free.
• Power is the two multiplied, and it is what turns into heat. Warm components are normal; hot ones are a warning.

The single most useful consequence: you choose the voltage, but the circuit chooses the current. A component fails when it is asked to pass more current than it was built for, which is why a stalled motor is dangerous to a driver board in a way a spinning one is not.

Short circuits, in one paragraph

A short circuit is a path from one side of the supply to the other with almost nothing in the way. With nothing to limit it, current rises until something gives: usually a wire getting hot, a battery venting, or a board releasing smoke. Nearly all bench shorts come from stray strands of wire, metal offcuts on the bench, or a battery connector touching a chassis.

Bench rules worth enforcing

• Eye protection whenever anything is cut, drilled or soldered.
• Batteries out of the robot when it is stored, and never charged unattended.
• A clear bench before wiring: loose metal parts and exposed conductors do not share a surface.
• Cut wire ends go in a bin immediately; offcuts are the most common cause of a mystery short.
• Hot tools return to their stand between every use, not at the end of the task.

Diagnosing before replacing

1. 01Does the board power up on its own, disconnected from the motors?
2. 02Does the battery hold voltage under load, or sag when the motors start?
3. 03Does the fault follow the component when you move it to another robot?
4. 04Does it follow the wire instead?

Answering those four in order finds most faults without a multimeter, and teaches the narrowing habit at the same time. Replacing parts until it works teaches neither.