Voltage must match
Supply voltage must stay within the allowed range for every connected device. Too much voltage can damage a component quickly. A supply’s current rating is capacity; the circuit draws the current it needs, provided the voltage is correct.
Logic power versus load power
A microcontroller may power LEDs and small sensors, but motors, pumps, relays, and servos can create current spikes and electrical noise. Give demanding loads an appropriate external supply and switching hardware.
Share ground for signals
Separate supplies usually need a common ground when one circuit sends a signal to the other. Without it, the signal voltage has no shared reference.
Avoid common bench mistakes
- Check polarity before applying power.
- Set an adjustable supply voltage before connecting the circuit.
- Do not move breadboard wires while energized.
- Add current limiting when testing an unfamiliar circuit.
- Disconnect immediately if a part heats unexpectedly.
Batteries are not all equivalent
A rectangular 9 V battery is poor for many motor or servo projects because it cannot sustain large current. Use a regulated USB supply or suitable battery pack matched to the load.