Recipe

Check a circuit before you power it

Use when: you have built or changed a circuit and are about to plug in USB or a battery

Goal: power applied only to a circuit that matches its plan, with no short across the supply

Taught in A safe workspace

1. 1

   Make every change with the USB cable and battery disconnected.

   Example

   Unplug the ESP32-S3 board's USB cable before moving any jumper.

   Why: a wire brushing the wrong pin can't short anything that has no power.

2. 2

   Confirm which voltage the circuit is getting, and that it matches what its parts expect.

   Example

   A 3.3 V sensor goes on the board's 3V3 pin, not its 5V pin.

   Why: too high a voltage can destroy a part the moment power arrives.

3. 3

   Follow every wire from the supply pin and make sure none of them reaches ground without passing through a part.

   Example

   A jumper from the + rail straight to the − rail is a short; remove it.

   Why: a short is the one fault that turns a low-voltage circuit into a hot one.

4. 4

   Plug in, then look, listen and sniff for a few seconds.

   • nothing hot, no smell, power LED on — carry on.
   • anything hot, a burning smell, or the USB port drops out — unplug at once and recheck.

   Why: heat and smell arrive before damage spreads, so the first seconds tell you most.