DC fan (5 V, 40 mm) · Exterior view
Propeller blades (7)Label: 5 V 0.10 AFrame (PBT) · 40 × 40 × 10 mmRed (+) / black (−) wire
Square frame, impeller, corner holes and red-black wires
≈ 40 × 40 × 10 mm; four corner mounting holes
Outputs

DC fan (5 V, 40 mm)

In simple terms
What is this?

A propeller that cools by pushing air. It has its own small driver circuit inside.

What is it for?

Pushes the hot air out of the box so the circuit works without overheating.

Where do you see it?

Small fans inside the computer and the power supply.

How do you spot it?

A square frame with a propeller in the middle; the frame has four corner holes and two wires.

Caution:

Do not connect plus and minus reversed, the electronics inside get damaged; do not supply it directly from a microcontroller pin.

Technical definition

A cooling fan in which the brushless DC motor that spins the propeller and its driver circuit sit in the same housing. The two-wire example only takes a power supply; it has no speed feedback or separate PWM input. Because of the electronics inside, reversing the polarity does not safely change the rotation direction.

Power supply5 V DC
Current≈0.1 A
Size40 mm
Schematic symbol Same in IEC and ANSI

IEC 60617: the drawing style used in Türkiye and Europe.

Pins 2
1Positive supply (p)Red wire, +5 Vp
2Negative supply (n)Black wire, supply returnn
Features typical
Power supply
5 V DC
Current
≈0.1 A (depends on model)
Power
≈0.5 W
Wires
2; red +, black −
Motor
Brushless, with built-in driver
Inrush current
Greater than the running current; check the datasheet
Speed control
Supply PWM only if the manufacturer allows it
Example part
40 × 40 × 10 mm, 5 V two-wire fan
Common mistakes
Reversing the polarityThe internal driver can be damaged by reverse supply; red connects to plus, black to minus.
Powering from the pinFor about 100 mA and the starting current, use a separate supply and a suitable driver.
Stopping the propellerA stuck fan cannot cool and may heat up. Keep the blades free; check the PWM compatibility of a two-wire fan.

Test with a multimeter

Test whether this part is good with the multimeter on the measurement screen.

Take a measurement
Where it is used
Electronics enclosure coolingAirflow experimentSwitching on and off with a MOSFET
Related lessons
Driving a motor with a MOSFET
Module 4 · Diode and transistorsoonMeasuring current and the fuse
Module 2 · Measuring with a multimetersoon
Try it in the Lab