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Universal Input 24V AC-DC Power Supply

A universal input AC-DC power supply system providing a regulated 24V DC output for prototyping.

Intermediate Project — Handling mains AC voltage (120V/240V) requires strict safety protocols, proper grounding, and insulation to prevent electric shock or fire.
Assumptions:
  • The user needs a complete AC-to-DC solution, not just a DC-DC converter.
  • The power requirement is moderate (approx 30-60W) for general prototyping.
  • A microcontroller is required to monitor the output voltage and status as per standard requirements.

Bill of Materials

Microcontroller
Top Pick ESP32-DEVKITC-32E Espressif Systems From our database
The ESP32-DEVKITC-32E is the best choice because it allows you to easily add wireless telemetry to your power supply prototype, enabling you to monitor the 24V rail from a smartphone or PC.
Mouser $10.00 (1,043 in stock)
NUCLEO-F401RE STMicroelectronics From our database
Industry-standard ARM Cortex-M4 with excellent ADC resolution for precise power rail monitoring and professional toolchain support.
ARDUINO-UNO-R3 Arduino
The gold standard for beginner prototyping with massive library support for basic power monitoring and simple displays.
Power Supply
Top Pick LRS-50-24 MEAN WELL
The LRS-50-24 is the recommended choice due to its high availability, low cost, and proven reliability in prototype environments requiring a 24V rail from universal AC mains.
Mouser $11.40 (2,748 in stock)
VGS-50W-24 CUI Inc.
Chassis-mount industrial supply with universal input (85-264VAC), 24V/2.1A output, and screw terminals ideal for safe prototyping.
LS50-24 TDK-Lambda
Highly reliable industrial grade supply that handles 85-264VAC automatically with excellent efficiency and MTBF.

Compatibility Notes

  • The 24V output from the power supply must be stepped down to 5V or 3.3V to power the Microcontroller block; use a buck regulator for this.
  • Ensure the AC input wiring follows local color-coding standards (Black/White/Green for NA, Brown/Blue/Yellow-Green for EU).

You'll Also Need

  • AC Power Cord (NEMA 5-15P or CEE 7/7)
  • Enclosure/Project Box for safety
  • Voltage divider resistors (for sensing 24V with 3.3V/5V logic)
  • Fuse and Fuse Holder for AC input protection
  • DC Step-down module (e.g. 24V to 5V) for MCU power
Estimated BOM Cost: $25-30 (based on live distributor pricing)

Design Considerations

High Voltage Safety
Since this involves 120V/230V AC, the power supply must be mounted in a non-conductive or properly grounded earthed metal enclosure. Ensure creepage and clearance distances of at least 8mm are maintained between AC traces and low-voltage DC signals.
Thermal Management
At 50W output, even an 85% efficient supply generates ~7.5W of heat. Ensure the enclosure has adequate ventilation or a small 24V fan if the supply is under continuous heavy load to prevent thermal shutdown.
Voltage Monitoring Accuracy
To monitor the 24V rail with an MCU, use a precision voltage divider (0.1% tolerance resistors) and a 3.3V Zener diode for over-voltage protection on the ADC pin. Calibrate the firmware to account for resistor tolerances and MCU internal reference drift.
Inrush Current
Switching power supplies like the LRS-50-24 have high inrush currents (up to 45A @ 230VAC). Ensure any upstream circuit breakers or power strips are rated for these transient spikes to avoid nuisance tripping.

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