L9110S H-Bridge Driver: Wiring Two DC Motors Safely

Quick answer

Power the L9110S motor supply from a separate battery or adapter, tie its ground to the Arduino ground, and test one motor at a time before connecting the second.

Step-by-step L9110S wiring and test sequence

1. Set up the motor power supply first: Connect the motor supply to the L9110S motor power terminals and leave the Arduino disconnected. Check the polarity with a multimeter before plugging anything in. Common mistake: powering the board from the Arduino 5 V pin, which can brown out the board when the motors start. Confirm the supply voltage is within the module's supported range before any motor is attached.
2. Tie the grounds together: Run a wire from the motor supply ground to the Arduino ground and to the L9110S ground. Without a common ground, the input signals have no reference and the motors may twitch or not turn. Checkpoint: measure continuity between all three ground points. A missing common ground is the most common reason a correctly wired L9110S appears dead.
3. Wire motor A to one side and motor B to the other: Connect the first motor across the A terminals and the second across the B terminals, keeping the two motor wires in the same order on each side. Do not connect motor power to the logic input pins. Checkpoint: tug each wire gently to confirm the terminal is clamped on conductor, not insulation. Label motor A and motor B now so direction fixes later are unambiguous.
4. Connect the logic inputs to the Arduino: Wire the A-direction and A-speed inputs to two Arduino digital pins, and the B-direction and B-speed inputs to two more. Keep the input wires short and away from the motor leads. Common mistake: assuming the inputs are labeled with the same pin names as another driver board; follow the silkscreen on the L9110S you received. Record which Arduino pin drives each input before writing code.
5. Upload a one-motor test sketch: Write a sketch that sets one direction pin high, the other low, and pulses the speed pin with analogWrite. Run motor A for two seconds, stop, then reverse. Do not connect motor B yet. Checkpoint: if the motor only hums, disconnect power and recheck the A wiring before changing the code. A single-motor test separates a code problem from a wiring problem.
6. Add the second motor and test both directions: Once motor A runs forward and reverse, repeat the sketch for motor B. Then run both motors together and watch the supply voltage. A dip that resets the Arduino means the supply is too weak or the motors are drawing more than expected. Common mistake: blaming the L9110S for a supply that cannot deliver the combined startup current. Test both motors together only after each one passes alone.
7. Check heat and stop if the board is hot: After a few minutes of running, touch the driver chip briefly. It should be warm, not painful. If it is too hot to hold, disconnect power and reduce the load or change to a driver rated for more current. The L9110S has no current limit adjustment, so heat is your main warning sign. Treat a hot chip as a load problem, not a code problem.

Product facts

• 5x L9110S H-bridge Dual DC Stepper Motor Controller Board: The 5x L9110S H-bridge pack contains five compact dual DC and stepper motor controller boards. Having five boards lets you wire one motor pair per board and keep a spare for a second prototype or a replacement after a wiring mistake.