Description: Complete guide to selecting the perfect SMPS power supply for Arduino, Raspberry Pi, industrial automation, and IoT projects. Learn about voltage, current, isolation, and sizing.

How to Choose the Right SMPS for Your Electronics Project

Choosing the correct SMPS (Switched-Mode Power Supply) is critical for your project’s reliability and performance. Whether you’re building an Arduino prototype, industrial automation system, or IoT device, this guide will help you select the perfect power supply.

Step 1: Determine Your Voltage Requirements

Different components operate at different voltages. Here are the most common requirements:

• 3.3V: Modern microcontrollers (ESP32, nRF52, STM32), wireless modules, low-power sensors
• 5V: Arduino, Raspberry Pi, USB devices, logic ICs, most sensors
• 9V: Guitar effects pedals, audio circuits, some analog systems
• 12V: DC motors, relay coils, LED strips, automotive electronics, fans
• 15V: Op-amps, analog signal conditioning, precision instrumentation
• 24V: Industrial automation (PLC standard), pneumatic valves, industrial sensors

Pro Tip: If your project uses multiple voltage levels (like 5V for a microcontroller and 12V for motors), consider a dual-output SMPS like the EasyPower SO12V51000 instead of buying two separate units.

Step 2: Calculate Current Requirements

Current (measured in milliamps or amps) determines how much power your SMPS needs to supply. Here’s how to calculate it:

1. List all components and their current draw
2. Add them up to get total current
3. Add 20-30% safety margin for reliable operation

Example: Arduino + Sensors Project

• Arduino Uno: 50mA
• Three ultrasonic sensors: 15mA × 3 = 45mA
• OLED display: 20mA
• WiFi module: 200mA (peak)
• Total: 315mA
• With 30% margin: 410mA
• Recommendation: SO5V500 (5V/500mA) ✓

Common Component Current Draw Reference

• Arduino Uno: 40-50mA
• Arduino Nano: 20-30mA
• Raspberry Pi 3: 500-800mA (up to 2.5A with accessories)
• Raspberry Pi 4: 600-1000mA (up to 3A with accessories)
• ESP8266: 80-170mA (peak 250mA)
• ESP32: 160-260mA (peak 500mA)
• Small DC motor: 100-500mA
• Relay (12V): 70-100mA
• LED strip (per meter, 12V): 400-800mA
• Servo motor (standard): 100-600mA (depending on load)

Step 3: Isolated vs Non-Isolated – Which Do You Need?

Choose Isolated SMPS When:

• Humans will touch your device’s output circuitry
• You need to eliminate ground loops in multi-board systems
• Safety standards require galvanic isolation
• You’re working with sensitive analog measurements
• Building medical or safety-critical equipment

Example: EasyPower SOID12V provides isolated 12V outputs

Choose Non-Isolated SMPS When:

• Space is extremely limited
• Cost is a primary concern
• The device is fully enclosed and not user-accessible
• Ground loops aren’t a concern (single-board systems)

Example: EasyPower SO12V1000 (open frame) for compact designs

Step 4: Consider Physical Size and Mounting

PCB Mountable SMPS

These mount directly onto your circuit board, saving space and eliminating external adapters. Perfect for:

• Production devices where size matters
• Custom circuit boards and prototypes
• Panel-mounted control systems
• Embedded systems requiring tight integration

Enclosure vs Open Frame

• Open Frame: Smallest size, best for enclosed projects or when space is critical
• With Enclosure: Better protection, safer handling during assembly, slightly larger

Step 5: Environmental Considerations

Operating Temperature

Most EasyPower SMPS operate reliably from -20°C to +70°C. If your application exceeds this:

• Add a heat sink or fan for high-temperature environments
• Derate the power supply (use 80% of rated capacity)
• Consider enclosed models with better thermal management

Harsh Environments

For dusty, humid, or industrial environments, choose epoxy-potted SMPS like all EasyPower models. The epoxy resin provides:

• Moisture resistance
• Dust and contaminant protection
• Vibration resistance
• Improved thermal dissipation

Step 6: Special Cases – Dual Output and Bipolar Supplies

When You Need Dual Outputs:

Different Voltage Levels:

• 3.3V + 5V for mixed-logic systems → SO3V35400 or SO3V352000
• 5V + 12V for microcontroller + motor systems → SO12V51000

Positive and Negative (Bipolar):

• Op-amp circuits needing ±15V → SO15VPN
• Audio amplifiers needing ±12V → SO12VPN
• Analog signal conditioning needing ±5V → SO5VPN

Decision Flowchart

START
  ↓
What voltage? → 5V / 12V / 24V / Other
  ↓
Calculate current (with 30% margin)
  ↓
Do you need isolation? → YES: Choose SOID model / NO: Continue
  ↓
Need dual outputs? → YES: Choose dual model / NO: Single output
  ↓
Size constraint? → CRITICAL: Open frame / NORMAL: Enclosure
  ↓
Industrial environment? → YES: All EasyPower have epoxy potting ✓
  ↓
Select your SMPS!

Real-World Examples

Project: Raspberry Pi Smart Home Hub

• Voltage: 5V
• Current: Raspberry Pi 4 (up to 3A) + USB accessories (500mA) = 3.5A total
• Recommendation: Use external 5V/3A adapter OR SO5V2000 (2A) for light use only
• Note: Raspberry Pi 4 needs 3A under full load; use 2A model only for headless servers

Project: Industrial PLC Control Panel

• Voltage: 24V (industry standard)
• Current: PLC inputs (200mA) + sensors (150mA) + indicator lights (100mA) = 450mA
• Environment: Factory floor (dust, vibration)
• Recommendation: SO24V500 (24V/500mA with enclosure and epoxy potting)

Project: Guitar Multi-Effects Pedal Board

• Voltage: 9V (standard for pedals)
• Current: 4 pedals × 150mA average = 600mA
• Recommendation: SO9V1000 (9V/1A)
• Bonus: Clean power reduces noise in audio circuits

Common Mistakes to Avoid

1. Underestimating current: Always add 20-30% safety margin
2. Ignoring peak current: Motors and servos draw 3-5x their nominal current on startup
3. Using non-isolated SMPS for user-accessible devices: Safety hazard!
4. Forgetting thermal considerations: Enclosed spaces need ventilation
5. Wrong input voltage: Check if your mains is 110V or 230V

Need Help Deciding?

Contact EasyPower technical support on WhatsApp: 8668319990

We can help you:

• Calculate exact current requirements
• Choose between isolated and non-isolated designs
• Recommend the optimal model for your application
• Provide technical datasheets and integration guidance

Browse all EasyPower SMPS models →