Why My First LED Strip Installation Flickered (And How to Fix Yours)
I installed a 5-meter RGB strip under my cabinets, plugged it into the included power supply, and it flickered every time I turned on the microwave. The problem wasn't the strip — it was the power supply. The cheap wall adapter that came with the kit couldn't handle the inrush current when the microwave compressor kicked on. I replaced it with a proper Mean Well power supply and the flickering stopped. The power supply is the most overlooked part of any LED strip installation. Getting it wrong means flicker, dimming, or a fire risk. Here's what I've learned.
12V vs 24V: Which Voltage Is Right for Your LED Strip?
12V is more common and cheaper. 24V is better for longer runs. Here's the rule: for runs under 5 meters, 12V is fine. For 5-10 meters, use 24V. The reason is voltage drop — as electricity travels along the strip, voltage decreases. At 12V, a 5-meter RGBW strip drawing 3A drops enough voltage that the far end is noticeably dimmer. At 24V, you can run 10 meters before the drop becomes visible. I use 12V for all my short accent strips (TV backlight, bookshelf) and 24V for long runs (under cabinets, ceiling coves). Check your strip's specifications — some are only available in one voltage. My LED Strip hub has a voltage selection table.
How Many Amps Does Your LED Strip Power Supply Need?
Calculate total wattage first: strip power draw per meter × total length. A 12V RGBW strip drawing 14.4W per meter (1.2A/m) over 5 meters needs 72W (6A). Add 20% safety margin: 72W × 1.2 = 86.4W. Round up to the next standard power supply size — 100W (8.3A at 12V). I keep a calculator table on my phone for this. Always oversize by at least 20%. An undersized supply runs hot and fails early. An oversized supply runs cool and lasts years. Mean Well LRS-100-12 ($18) is my go-to for 12V strips up to 8 meters. For 24V, the LRS-100-24 ($18) handles up to 10 meters.
How Do You Fix Voltage Drop on Long LED Strip Runs?
Voltage drop is physics: the strip furthest from the power source gets less voltage and becomes dimmer. At 12V, a 5-meter run typically drops to 10.5V at the far end — about 20% dimmer. At 10 meters, the drop can exceed 30%. Two fixes: use 24V strips (which halve the current for the same wattage), or inject power at multiple points along the strip. Power injection means running additional wires from the power supply to the midpoint or far end of the strip. I use 18 AWG wire for power injection runs up to 5 meters. For installations over 10 meters, I split the strip into sections with separate power supplies. See my installation guide for wiring diagrams.
Can You Use a Dimmable Power Supply for LED Strips?
You can, but PWM dimming (pulse-width modulation, which is what most LED strip controllers use) works better with a constant-voltage supply. A dimmable (variable-voltage) power supply is more expensive and harder to find. I recommend using a standard constant-voltage 12V or 24V supply with a separate PWM controller. The controller handles dimming and color, and the power supply just provides clean DC. My setup: Mean Well constant-voltage supply → RGBW controller → LED strip. The controller I use ($25 from Amazon) supports RF remote, WiFi, and voice control via Alexa.
References
- Mean Well Power Supply Specs — Manufacturer specifications for LED power supplies.
- Adafruit LED Strip Power Guide — Technical power calculation guide for LED strips.