What is SMD and what can it be used for in signage and decorative lighting?
Many people think all LEDs on the market are the same, but there are actually many types. The most popular type is LED SMD (economical, bright, safe), making it widely used in architectural decoration, automotive applications, furniture, and advertising signage.
LED SMD (Surface-Mount LED) evolved from traditional lamp-type LEDs. Its main advantage is its flexibility in being assembled into various sizes and shapes of panels/strips. The most popular format is the Strip light.
With its strip format, it can be easily cut, joined, bent, and is available in weather-resistant grades for outdoor use (it is important to choose the appropriate Outdoor/IP rating for the specific application). Users often refer to them as "chips" because the LED itself is tiny with minimal leads.
Structure and SMT Technology
SMDs are soldered onto circuit boards using Surface Mount Technology (SMT), which requires specialized tools and skilled technicians for production/repair.
Generally, SMDs use currents of approximately 20 mA–1 A and voltages of 2–3.6 V. They consume very low power compared to incandescent bulbs (~1/8) and fluorescent lamps (~1/4), support multiple colors, and are suitable for signage/decorative applications that require value for money.
Popular SMD Models
| Model | Chip Size (mm) | Average Brightness* | Key Features |
|---|---|---|---|
| SMD 3528 | 3.5 × 2.8 | ~5–6 lm/chip | Economical, used for decorative lighting/low-power strip lights |
| SMD 5050 | 5.0 × 5.0 | ~12–14 lm/chip | Brighter, supports RGB colors, popular for signage/effect lighting |
| SMD 5630 | 5.6 × 3.0 | ~20–23 lm/chip | Very bright, suitable for areas requiring high visibility |
| Others | 2835 / 3014 / 3030 | Varies by manufacturer | Found in various decorative and signage applications |
* Light values are reference ranges, depending on manufacturer/color temperature/test conditions.
Reasons for popularity in signage
- Low heat accumulation reduces the burden on the cooling system in light boxes.
- High lumen-per-watt, long lifespan, compact size for easy concealment.
- Available with various IP ratings (Indoor/Outdoor) and selectable color temperatures.
Installation and Power Supply
Choose a Switching Power Supply that matches the voltage/current of the load. In some cases, a resistor (R) is needed to limit the current, which can be calculated using:
Formula: R = (Vdc − Vf) / I (Ohms)
- Vf = Forward voltage drop across the LED
- I = Current required by the LED (Amperes)
- Vdc = Supply voltage
Example: Vf=2V, I=20mA(0.02A)
- 5V Supply → R = (5−2)/0.02 = 150 Ω
- 9V Supply → R = (9−2)/0.02 = 350 Ω
- 12V Supply → R = (12−2)/0.02 = 500 Ω
Safety and Recommendations
- Powering with 12–24V DC is safer than household AC power for signage applications.
- Choose the appropriate Outdoor + IP rating if exposed to sun/rain/moisture.
- Leave space for heat/air dissipation in light boxes and secure wiring properly.