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1. Test Objectives
- Validate the impact of varying LED counts (60/120/128) on the brightness, luminous flux, illuminance, and uniformity of flexible LED strips to provide data support for product development.
- Test the effect of different power settings on brightness for flexible PCB LED strips with varying widths (8/100).
- Validate the feasibility of designing high-brightness flexible LED strips with 128 LEDs per meter.
- Verify brightness differences among LED chips with varying color temperatures.
2. Test Sample
| Item | Number of LEDs | Pitch of the LED | Length of the LED Strip | Number of Samples |
| 1 | 60 LEDs/m | 16.67 | 1m | 4PCS |
| 2 | 120 LEDs/m | 8.33 | 1m | 4PCS |
| 3 | 128 LEDs/m | 7.81 | 1m | 2PCS |
3. Test Method
1. Record the original data of the LEDs.
2. Test LED strips with different specifications (60 LEDs/m, 120 LEDs/m, and 128 LEDs/m) using an integrating sphere and a spectrophotometer. Record corresponding data including luminance, luminous efficacy, color rendering index, and color temperature.
4. Measurement Equipment and Environment
Integrating sphere optical test system / High-precision spectrophotometer
Temperature: 28°C ±5°C
Humidity: 65% ±5%
Test Voltage: DC12V / DC24V
5. Test Date: September 15, 2023
6. LED Integrating Sphere Test Data
LED chip type for this sample: SMD2835; Sample supplier: Smalite LED.
| Smalite LED SMD2835 Test Data | |||||||||||
| CCT | Power | LED Current | LED Voltage | Luminance | Test Brightness | Voltage | lm/W | CCT | Ra | Wave length | Remark |
| 3000K | 0.2W | 60mA | 3.1-3.2V | 22-24 lm | 23.84 lm | 3.139V | 127 lm/W | 3032K | 80.9 | 582.3nm | |
| 4000K | 0.2W | 60mA | 3.0-3.1V | 24-26 lm | 25.82 lm | 3.129V | 138 lm/W | 4080K | 81.1 | 577.6nm | |
| 4000K | 0.2W | 60mA | 2.9-3.0V | 29-31lm | 31.2 lm | 2.883V | 181.2 lm/W | 4112K | 81.2 | 576.8nm | 128LEDs/m use |
7. Comparison of Test Data for LED Strips with Different Numbers of LEDs
| CCT | LEDs/m | Voltage | LED Current | Resistance | W/m | LED Power | Flux(lm) | lm/W | Wave Length(nm) | Ra | CCT | PCB Width |
| 3000K | 60 | DC12V | 25mA | 56+75Ω | 6.0W | 0.2W | 659.0 | 109.8 | 583.0 | 82.50 | 2955K | 8mm |
| 3000K | 120 | DC12V | 21mA | 160Ω | 9.8W | 0.2W | 1113.2 | 113.1 | 583.1 | 82.40 | 2956K | |
| 4000K | 60 | DC12V | 25mA | 68+68Ω | 5.8W | 0.2W | 679.4 | 117.1 | 577.2 | 82.60 | 4085K | 8mm |
| 4000K | 120 | DC12V | 20mA | 330/360Ω | 9.5W | 0.2W | 1119.1 | 117.8 | 577.4 | 82.80 | 4087K | |
| 3000K | 60 | DC12V | 50mA | 56Ω | 11.88W | 0.2W | 1145.4 | 98.75 | 583.2 | 81.90 | 2959K | 10mm |
| 3000K | 120 | DC12V | 40mA | 68Ω | 19.3W | 0.2W | 1953.2 | 99.86 | 583.2 | 82.00 | 2973K | |
| 4000K | 60 | DC12V | 49mA | 62Ω | 10.8W | 0.2W | 1150.8 | 106.5 | 577.4 | 82.00 | 4058K | 10mm |
| 4000K | 120 | DC12V | 41mA | 75Ω | 18.6W | 0.2W | 1964.0 | 106.7 | 577.5 | 82.50 | 4116K | |
| 4000K | 128 | DC24V | 31mA | 68Ω | 11.6W | 0.2W | 1912.9 | 165.4 | 577.9 | 82.70 | 4010K | 10mm |
| 4000K | 128 | DC24V | 26mA | 82Ω | 10.0W | 0.2W | 1696.0 | 169.6 | 577.9 | 82.70 | 4000K | |
8. Test Data Analysis
- Impact of Different LED Quantities on Brightness (Luminous Flux, Illuminance, Uniformity):
- The luminous efficacy difference between 60 LEDs/m at 6W/m and 120 LEDs/m at 10W/m is 3%;
- The luminous efficacy of 60 LEDs/m at 12 W/m is close to that of 120 LEDs/m at 20 W/m, with minimal difference between them.
- 120 LEDs/m achieved the highest luminous efficacy at 169.6 lm/W, with a 4.2 lm/W difference between 12W and 10W power settings.
The table shows a positive correlation between LED count and luminous flux, confirming that “more LEDs result in higher brightness.”
- Effect of PCB Width on Brightness
- For 60/120-LED designs rated at 6W and 12W/m (lower power), with LED current set below 25mA, an 8mm-wide PCB adequately meets thermal and power requirements.
- 60/120 LEDs achieving 12W and 20W operate at maximum power with currents near full load. A 10 mm-wide PCB is required to handle higher currents and improve heat dissipation, preventing brightness degradation due to overheating.
- 128 LEDs achieve 170 lm/m at 10W/m with a current of only 16 mA, indicating low power consumption. An 8 mm-wide PCB can be considered.
PCB width does not affect brightness, but PCB trace width is positively correlated with current carrying capacity: wider traces provide greater cross-sectional area, reducing trace resistance and allowing higher power settings for the light strip.
Power underpins brightness: more LEDs → higher power → greater brightness. PCB width is crucial for stable power delivery. A 10 mm-wide PCB reduces impedance and enhances heat dissipation, indirectly supporting high brightness.
- Feasibility of 128 LED/m High-Brightness Flexible Strip Design
- The luminous flux of 128 LEDs far exceeds that of 60/120 LEDs, meeting the “high brightness” requirement;
- The 128-LED configuration operates at 11.6W and 10.0W, featuring a well-balanced design with manageable power consumption. The 10 mm PCB width provides stable support, while the drive currents of 31 mA and 26 mA remain within reasonable ranges.
Table data confirms the 128-LED design excels in luminous flux, power handling, and color temperature compatibility, validating its feasibility.
- Luminous Efficiency Differences Across Color Temperatures
- 60 LEDs/m at different color temperatures under 6W power: 3000K efficacy is 109.8 lm/W, and 4000K efficacy is 117.1 lm/W, a difference of 7.3 lm/W.
- 120 LEDs/m at different color temperatures under 10W power: 3000K efficacy is 113.1 lm/W, and 4000K efficacy is 117.8 lm/W, a difference of 4.7 lm/W.
The brightness difference between color temperatures remains significant. For the same chip, 3000K warm-white LEDs are approximately 10% brighter than 4000K warm-white LEDs.
4000K warm white light by approximately 10% (see LED integrating sphere test data above: 3000K brightness: 22-24 lm; 4000K LED brightness: 24-26 lm. Therefore, this factor must be fully considered when designing LED strips with different color temperatures.
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