Run this list before you connect a battery or plug in the supply for the first time. It catches the common wiring mistakes that burn drivers and regulators. It is general guidance for low voltage hobby and bench builds, not a substitute for the part datasheets or a qualified person. Do not use it for mains wiring.
Power
- Battery or supply voltage matches every part’s rated input. Check the motor driver, regulator and board.
- Polarity checked with a multimeter before connecting, red on positive.
- A fuse or a current-limited bench supply is in the path.
- Wire thickness suits the current, and joints are soldered or crimped, not just twisted.
- The microcontroller has a clean supply that does not share a thin wire with the motors.
- Common ground joins the motor supply and the logic side.
Signals
- Logic levels match: 3.3 V boards are not driven directly by 5 V signals. Use a level shifter where needed.
- No two pins are assigned to the same job. Check pin maps with the wiring checker.
- Pins used at boot on your board are not held high or low by a connected part.
- Pull-ups are present on I2C lines.
Mechanical
- Wheels are off the ground or the robot is on a stand for the first motor test.
- Loose wires cannot reach moving parts.
- Batteries are secured and cannot short against metal.
- You have a way to cut power fast, such as a switch within reach.
First power-up
- Power on with motors disconnected and watch for heat, smell or a hot regulator.
- Check supply rails with the multimeter before trusting them.
- Add one subsystem at a time: logic, then sensors, then motors.
- Keep a test log. The bill of materials and test log template gives you one.
If a board resets when the motors start, see the ESP32 brownout fix. Calculate battery runtime in the battery runtime calculator. More on safe habits is in the Learn hub.
Last reviewed: November 2026. Free to copy and adapt for your own project, with credit. Written, checked and maintained by Jignesh Panchal of Jaadu Digital. See the editorial standard.
Meter checks before the first power-up
With the battery disconnected, set the multimeter to continuity or resistance and measure between the supply positive and ground at the point where the battery will connect.
- A reading of close to zero ohms that stays there means a short. Find it before you connect power. Common causes are solder bridges, a stray strand of wire, or a part fitted backwards.
- A reading that starts low and then rises is usually capacitors charging. It is normal.
- A very high or open reading is normal for an unpowered board. A reading of a few hundred ohms or more usually indicates no short.
- Repeat between the 3.3 V or 5 V rail and ground on the board.
Using a current-limited supply
If you have a bench supply, set the voltage to the battery value and the current limit low, for example just above what the logic board should draw. Raise it as you add subsystems. If the supply drops to the limit as soon as you switch on, switch off and look for a short or a wrong connection.
What the readings mean
- Rail voltage far from the expected value: the regulator is wrong, overloaded or fitted incorrectly.
- Part heats within seconds: switch off, and check polarity, voltage and that the part is not overloaded.
- Board resets when a motor starts: the supply sags during the current surge, so check the wiring, add decoupling and consider a separate supply.
Common mistakes
- Powering the motors and logic from one thin wire.
- Testing with the wheels on the ground, so that a wrong command makes the robot run off the bench.
- Skipping the datasheet for the regulator’s input and output limits.
- Connecting a battery of a different chemistry or voltage because the connector fits.