LED PSU Calculator

Immediate symptoms:

• ▸LEDs appear dim or colors are incorrect (especially white appears yellow/orange)
• ▸Flickering or intermittent operation
• ▸Animations run slower than expected
• ▸Some LEDs don't light up at all

Long-term damage:

• ▸Power supply runs excessively hot and fails prematurely
• ▸Thermal shutdown protection activates, cutting power completely
• ▸Voltage sag damages LED driver circuits
• ▸Fire hazard in extreme cases

Always size your PSU at least 20% above your calculated maximum draw

to prevent these issues and ensure safe, reliable operation.

Benefits of oversizing:

• ▸Longer PSU lifespan due to cooler operation (less thermal stress)
• ▸Room for future expansion without replacing PSU
• ▸Better efficiency at typical load levels (most PSUs are most efficient at 50-80% load)
• ▸Reduced electrical noise and ripple
• ▸More stable voltage under varying loads

When oversizing becomes wasteful:

• ▸Only excessive oversizing (5x+ your needs) wastes money on upfront cost
• ▸Very low loads (<10% of PSU capacity) may reduce efficiency slightly
• ▸Larger physical size may not fit in your enclosure

Sweet spot:

A 100W PSU powering a 60W LED installation is ideal - plenty of headroom without waste.

Correct wiring method:

1. Run separate positive (+) and negative (-) wires from the PSU to each strip's input 2. Use a terminal block or distribution board to split PSU output to multiple strips 3. Never run power through one strip to feed another (daisy-chaining causes voltage drop)

Wire gauge considerations:

• ▸Calculate total current: sum of all strips
• ▸Use appropriate wire gauge based on total current and longest distance
• ▸Thicker wire for longer runs to minimize voltage drop

PSU sizing:

• ▸Total PSU wattage must cover the sum of ALL strips plus 20% safety margin
• ▸Example: Three 20W strips = 60W + 20% = 72W minimum PSU

For addressable LEDs:

• ▸Power in parallel (separate wires to each strip)
• ▸Data in series (DOUT of strip 1 connects to DIN of strip 2)

Inject power when:

• ▸5V strips exceed 2.5 meters - inject every 2.5m for best results
• ▸12V strips exceed 5 meters - inject every 5m
• ▸24V strips exceed 10 meters - inject every 10m
• ▸You see visible dimming or color shift at the far end
• ▸Running LEDs at full brightness (worst case for voltage drop)

How to inject power:

1. Connect additional power wires (+/-) to the strip's power pads at the midpoint or end 2. Run these wires back to your PSU (or use a second PSU) 3. Use the same wire gauge as your main power connection 4. Only connect power (+/-), NOT data signal

Pro tip:

For very long runs (10m+), inject power at BOTH the beginning and end of the strip, or every 5 meters for uniform brightness.

Yes, you should use a fuse for any installation over 60W.

Fuses protect against short circuits, wiring faults, and prevent fires.

Fuse sizing rule:

Choose a fuse rated at 125-150% of your expected maximum current.

Examples:

• ▸60W @ 5V (12A) → 15A fuse
• ▸100W @ 5V (20A) → 25A fuse
• ▸150W @ 12V (12.5A) → 15A fuse
• ▸300W @ 12V (25A) → 30A fuse

Fuse types for LED projects:

• ▸Automotive blade fuses: Cheap, easy to find, good for DC
• ▸Inline fuse holders: Mount on your positive wire between PSU and LEDs
• ▸Resettable fuses (polyfuses): Auto-reset after cooling

Important notes:

• ▸Fuse goes on the positive wire only
• ▸Place fuse as close to PSU as practical
• ▸A blown fuse indicates a problem to diagnose

5V strips (WS2812B, SK6812):

• ▸Individual LED control — best color effects and animations
• ▸Voltage drop limits practical runs to about 2-3 meters without power injection
• ▸Higher current draw means thicker wires needed
• ▸Ideal for: short accent strips, TV backlights, small matrices, desk lighting

12V strips (WS2815, WS2811, GS8208):

• ▸Good balance between addressability and run length
• ▸3-LED segments reduce power wiring complexity
• ▸Can run 5-7 meters before injection is needed
• ▸Ideal for: medium runs, staircases, under-cabinet, holiday displays

24V strips (COB, FCOB):

• ▸Lowest current for the same wattage — thinnest wires, least voltage drop
• ▸Can run 10+ meters on a single power connection
• ▸Mostly COB/FCOB for smooth, seamless light output
• ▸Ideal for: long runs, room perimeters, cove lighting, architectural

Rule of thumb:

Choose the highest voltage your controller and LED type support. Longer runs = higher voltage.

USB power limits:

• ▸USB 2.0: 2.5W (5V @ 500mA) — only a few LEDs
• ▸USB 3.0: 4.5W (5V @ 900mA) — about 15-20 WS2812B LEDs at full white
• ▸USB phone charger (5V/2A): 10W — about 30-50 LEDs at animation brightness
• ▸USB-C PD: up to 100W — viable for larger projects but needs a PD trigger board

When USB works:

• ▸Small accent strips under 30 LEDs
• ▸Low-brightness ambient effects (not full white)
• ▸Portable or temporary installations
• ▸Prototyping and testing

When you need a dedicated PSU:

• ▸More than 50 LEDs or over 10W total
• ▸Full-brightness white or sustained high output
• ▸Permanent installations that need reliability
• ▸Any 12V or 24V LED strips

Important:

Cheap USB chargers may not deliver their rated current reliably. For anything beyond a quick prototype, use a proper Mean Well or similar rated power supply.

How to set it:

1. Open WLED web interface → Config → LED Preferences 2. Find Maximum Current (in milliamps) 3. Set it to your PSU's rated output minus 20% headroom

Example calculations:

• ▸5V 10A PSU (50W): set to 8000 mA (80% of 10,000)
• ▸5V 20A PSU (100W): set to 16000 mA
• ▸12V 5A PSU (60W): set to 4000 mA

Why this matters:

• ▸WLED dims all LEDs proportionally when the limit would be exceeded
• ▸Prevents PSU overload, flickering, and brownouts
• ▸Your LEDs still look great — WLED is smart about which colors to dim
• ▸This is why our calculator's "Effects" mode is realistic: in practice, WLED rarely lets strips draw full power

Pro tip:

If your LEDs seem dimmer than expected, check this setting first. It may be set too low from a previous configuration.

When to use multiple PSUs:

• ▸Total power exceeds 300W (single PSUs get expensive and bulky above this)
• ▸LEDs are spread across different physical locations
• ▸You want redundancy in critical installations
• ▸Different voltage zones (e.g., 5V for short accents + 24V for long runs)

How to wire multiple PSUs safely:

• ▸Connect the negative/ground of all PSUs together — this is essential for data signals to work between segments
• ▸Each PSU powers its own section of LEDs on the positive wire
• ▸Never connect the positive outputs of two PSUs together
• ▸Data signal runs continuously across all segments

Wiring diagram concept:

• ▸PSU 1 (+) → LED segment 1 (+)
• ▸PSU 2 (+) → LED segment 2 (+)
• ▸PSU 1 (-) + PSU 2 (-) → common ground bus → all LED segments (-)
• ▸Data: Controller → DIN segment 1 → DOUT → DIN segment 2

Important safety notes:

• ▸All PSUs must output the same voltage for connected LED segments
• ▸Fuse each PSU's positive output independently
• ▸Use a ground bus bar or terminal block for clean common grounding