USB Fan Speed Controller Module A compact inline controller that gives precise, stepless speed control for common 5.0 V USB fans. Use it to set the exact airflow you need, reduce noise, and make fans easier to use with power banks, chargers, or computer USB ports. Key benefits - Precise stepless speed control: Smooth voltage adjustment across the output range to fine tune airflow and noise. - Broad input compatibility: Accepts DC 4 to 12 V power sources, making it compatible with USB chargers, power banks, and computer USB ports. - Simple user interface: Single rotary knob with built-in on/off switch; turn clockwise to increase airflow and counterclockwise to decrease. - Clear safety limits: Rated nominal power 5 W. Designed for use within specified input and output ranges to avoid overload. - Works with most common 5.0 V USB fans on the market. How it works - Input power range: DC 4 to 12 V. - Output voltage range: DC 2.5 to 8.0 V, adjusted smoothly by the knob. - Rated power: 5 W. Do not overload the controller. - Fan types: Standard non-adjustable fans typically use a 5 V direct-drive motor. Some two-speed fans include an internal step-up circuit. If a two-speed fan is set to the high position, its internal boost circuit can prevent speed adjustment by this controller. For two-speed fans, set the fan switch to a single (low) gear before using the controller to ensure variable control. Compatibility and usage - Designed for common 5.0 V USB fans. - Operation example: Plug the male USB of the controller into a charger, power bank, or computer USB port. Plug the fan into the controller. Alternatively, use a micro-USB 5.0 V power supply. - Knob functions as both speed adjuster and power switch for convenient inline control. Practical use scenarios - Desk cooling: Fine tune a USB desk fan to a comfortable airflow and low noise level while working. - Portable cooling: Connect a fan to a power bank and adjust runtime and comfort by reducing fan voltage as needed. - Electronics or hobby projects: Control airflow for small enclosures, Raspberry Pi cooling, or other USB-powered components where variable airflow is useful. Important notes - Keep input voltage within DC 4 to 12 V and output within DC 2.5 to 8.0 V. - Nominal power is 5 W. Do not exceed this rating. - For two-speed fans, set the fan to a single (low) gear before using the controller, otherwise speed adjustment may not be possible. This controller provides a straightforward, reliable way to add stepless speed control to USB fans while maintaining compatibility with common USB power sources.