Can I run a motor from a battery directly?

Yes — motor across the 4.5 V pack, nothing else, and it spins. To switch it from a sensor or a button you need a transistor, and either way add a 1N4001 across the motor to absorb kickback.

How much current does a small DC motor draw?

Typically 100–300 mA spinning freely on 3–4.5 V, rising to an amp or more if the shaft is stopped. Measure yours with a multimeter in series; the stall figure decides what transistor you need.

How do I make a DC motor spin the other way?

Swap its two wires. To do that under electronic control you need an H-bridge, which is what the L293D motor driver provides at Level 9.

part · Level 4 · Motion · output

How a small DC motor works

DC motor (3 V) — Turns electricity into spin.

What it is

A DC motor turns electricity into spin. Inside the metal can, coils of wire sit on a shaft between two permanent magnets. Current through a coil makes it a magnet too, the fixed magnets push it round, and a little rotating contact called the commutator flips the current direction every half turn so the push never stops.

Two wires, no fixed polarity: swap them and the motor runs the other way. That is how a robot reverses.

The "3 V" on the label is its comfortable operating voltage — small hobby motors usually run from 1.5 to 6 V, spinning faster with more volts. On the 4.5 V pack yours will spin briskly and get slightly warm, which is normal.

How it works

Current. A motor's coil has very low resistance, often just a few ohms. Spinning, it generates a voltage of its own that opposes the supply (back-EMF), and that keeps the current down to roughly 100–300 mA with nothing attached to the shaft. Stop the shaft with your fingers and the back-EMF vanishes: with a 3 Ω coil on 4.5 V that is 4.5 ÷ 3 = 1.5 A. That is the stall current, and it is why a motor can drain a pack and get hot in seconds.

Switching it. 300 mA is fine for a 2N2222 (600 mA max) and would burn the base if you connected it directly, so: base resistor, transistor on the − side. Base current needed ≈ 300 ÷ 200 = 1.5 mA — a 1 kΩ from the 4.5 V pack gives (4.5 − 0.7) ÷ 1000 = 3.8 mA, comfortably saturating it. Stall current, though, is past the transistor's rating; a small motor should not be held stalled.

The kickback. A coil hates having its current cut. When the transistor switches off, the coil's collapsing magnetic field throws out a voltage spike that can be tens of volts — enough to punch through a transistor. A 1N4001 diode across the motor, striped end toward +, gives that spike a safe loop to spin down through. It costs nothing in normal running because the diode is backwards to the supply.

Speed. Roughly proportional to voltage. Half the voltage, half the speed — which is what a pot or a pulsed transistor does in the next levels.

The numbers

Operating voltage	1.5 – 6 V — nominal 3 V; happy at 4.5 V
Running current, no load	≈ 100–300 mA — varies by motor — measure
Stall current	≈ 1 A or more — hot, drains the pack fast
Polarity	none — swap the wires to reverse
Kickback protection	1N4001 across it — band toward +

Mistakes everyone makes

Motor wired straight to the LED's 220 Ω lane. It barely twitches: 4.5 ÷ 220 ≈ 20 mA cannot spin it. Fix: motors get the transistor, not a resistor.
No flyback diode. Works for a while, then the transistor dies mysteriously. Fix: 1N4001 across the motor terminals, striped end to +.
Holding the shaft to "feel the torque". That is a stall — over an amp, a hot motor and a hot transistor. Fix: let it spin free or put a light load on it.
Running it from the same pack as a sensitive circuit and watching the LED flicker. The motor's current pulls the pack voltage down. Fix: a 100 nF capacitor across the motor and, later, a separate motor battery.
Loose breadboard wires from the motor. The motor's own leads are stranded. Fix: solder or crimp solid jumper ends onto them.

Questions people ask

Can I run a motor from a battery directly?: Yes — motor across the 4.5 V pack, nothing else, and it spins. To switch it from a sensor or a button you need a transistor, and either way add a 1N4001 across the motor to absorb kickback.
How much current does a small DC motor draw?: Typically 100–300 mA spinning freely on 3–4.5 V, rising to an amp or more if the shaft is stopped. Measure yours with a multimeter in series; the stall figure decides what transistor you need.
How do I make a DC motor spin the other way?: Swap its two wires. To do that under electronic control you need an H-bridge, which is what the L293D motor driver provides at Level 9.

Projects that use this part

🌀 First Spin — Your first motor. A switch, a coil, and a diode that catches the voltage kick when the current stops. L4 · 15 min
💨 Handheld Fan — Press the button, the fan spins. A tiny finger current commands a hundred-milliamp motor through a transistor. L4 · 20 min
🌞 Sunrise Fan — Sunrise Alarm with the LED swapped for a motor. The sun rises, the fan starts — an automatic wake-you-up desk breeze. L4 · 25 min
🆘 Panic Fan — Two buttons, either one fires the fan. Panic Doorbell wearing a motor — an OR gate that spins. L4 · 20 min
🎉 Party Spinner — One button, three mouths: a spinning motor, a red LED, and a buzzer all fire together. One transistor drives them all. L4 · 25 min
🚗 Twin Wheels — Two motors from one button — a Level 9 robot drivetrain, five levels early. L4 · 25 min
🎚️ Dial-a-Spin — Dial-a-Brightness with a motor instead of an LED. Twist the knob and watch the fan speed slide from full spin to a slow crawl. L4 · 20 min
🕸️ Trip Wire Fan — Trip Wire Alarm's brain wearing a motor. The wire is intact — the fan is silent. Snap it — the fan spins as the alarm. L4 · 25 min

verified against: SparkFun — Motors and Selecting the Right One · Adafruit — Motor Selection Guide · SparkFun — Transistors