JMX-FN03-U1.2 3 Step Fan Speed Control Mini Rechargeable Fan Circuit 3.7V-4.2V Small Fan Motherboard Low Voltage Fan Circuit 3.7V Circuit Rechargeable Circuit With 3 Level Speed Control For 18650 Battery 3.7V Battery

Short description: Compact PWM dimmer for brushed DC motors and a controller for 3.7V single-cell battery charging — not a boost converter (no coil/inductor).

The JMX-FN03-U1.2 is a compact PWM controller designed for motor speed control and simple 3.7V single-cell charge-control tasks. It outputs a pulse-width-modulated signal for smooth, efficient control of brushed DC motors and can be used in basic battery charging arrangements when paired with proper current limiting and protection. This board is not a boost converter — it contains no coil/inductor and will not raise voltage.

Key features

• True PWM dimmer for brushed DC motors — smooth speed control when used with an appropriate MOSFET or switch.
• Suitable for 3.7V single-cell battery charge-control with external current limiting and protection.
• Not a boost converter — contains no coil/inductor; does not step up voltage.
• Compact PCB for easy embedding in small projects and enclosures.
• Simple integration — add current limiting, charge-termination, and protection circuitry for safe charging.

Technical summary

• Model: JMX-FN03-U1.2
• Function: PWM motor dimmer & 3.7V charger controller
• Target voltage: single-cell 3.7V (Li-ion / LiPo)
• Topology: PWM switching (no coil / not a boost converter)
• Form factor: compact PCB — verify dimensions before installation

Usage notes & safety

• Intended for PWM control and basic charge-control — not a full-featured smart charger. Use current limiting and battery protection when charging.
• Do not expect voltage boost — use a proper boost converter to step up voltages.
• Recommended for hobby/DIY projects; verify wiring and test with a reliable power source and protection equipment before deployment.