MEAN WELL MDR-40-12 DIN Rail Power Supply 12V DC 3.33A 40W

Automation engineers and panel builders often need a reliable, compact power source that mounts directly onto a DIN rail without wasting space. The MEAN WELL MDR-40-12 delivers 12 V DC at up to 3.33 A, providing 40 W of clean, regulated power for industrial control systems, sensors, and small actuators. Its slim plastic housing and snap-on DIN rail mounting make it a practical choice for crowded enclosures.

Key specifications

• Output voltage: 12 V DC (adjustable from 10.8 to 13.8 V DC)
• Output current: 3.33 A
• Rated power: 40 W
• Input voltage: 85–264 V AC or 120–370 V DC
• Efficiency: up to 86% at 230 V AC full load
• Ripple and noise: 120 mVp-p
• Mounting: DIN rail TS-35/7.5 or TS-35/15
• Protection: overload, overvoltage, short circuit
• Operating temperature: -20 to +70 °C
• Isolation: 3 kV AC input to output
• Cooling: free air convection
• Safety standards: UL508, TUV EN60950-1, CB, CE
• MTBF: >600,000 hours
• Housing material: plastic
• Protection class: Class I

Why choose it

This power supply is built for continuous industrial use. Its universal AC input and wide DC input range mean it can be deployed almost anywhere in the world. The adjustable output lets you compensate for voltage drops in long cable runs. With a high MTBF and full protection suite, it reduces downtime and maintenance costs. The compact plastic housing is lightweight yet durable, and the DIN rail clip ensures secure mounting even in vibrating environments.

Ideal use cases

• Powering PLCs, HMIs, and industrial controllers
• Supplying sensors, transmitters, and relays
• Driving small motors, valves, and actuators
• Building automation and HVAC control panels
• Test and measurement equipment

Good to know

The MDR-40 series is known for its slim profile—only 40 mm wide—saving valuable rail space. The output voltage can be fine-tuned with a built-in potentiometer. Ensure proper ventilation around the unit; free air convection cooling requires at least 25 mm clearance above and below. For compliance, always install in a suitable enclosure and follow local electrical codes.