Quick answer: Color-changing LEDs vary the brightness of red, green and blue channels to mix colors; according to Wikipedia's RGB model explanation, these light contributions add together. For a strip that shows different colors at different positions, choose addressable RGB, as distinguished in Wikipedia's strip-type guide.
The useful choices are how the colors change, whether you need dedicated white light, and how much power the strip requires. This guide explains those choices and works through a low-voltage strip example; it does not rank bulbs or promise health effects from particular colors.
How does an RGB LED make millions of colors?
RGB mixes separate red, green and blue light contributions. According to Wikipedia's RGB model explanation, equal channel intensities produce shades of gray, with all channels at full intensity producing white in the model. Changing their relative intensities changes the mixture.
A concrete example is the WS2812B. According to the WorldSemi WS2812B datasheet, each primary-color channel has 256 brightness levels. The combination count is:
Combinations = red levels × green levels × blue levels = 256 × 256 × 256 = 65,536 × 256 = 16,777,216.
That is a count of channel settings. It should not be read as a measurement of how many differences a viewer can distinguish, or as a promise about every color-changing product. The count comes from this particular controller's channel resolution.
The individual emitter is not changing its semiconductor into another material. According to Wikipedia's LED explanation, an LED's emission color depends on the semiconductor energy gap. In an RGB system, the controllable quantity is the contribution from each colored emitter.
What does PWM do?
PWM controls the average electrical drive by changing the proportion of time a signal is on. Its duty cycle is the on-time divided by the complete cycle time; more on-time increases average voltage or current, as described in Wikipedia's PWM explanation.
Worked example: assumed PWM timing
Assume an ideal rectangular signal is on for 1 millisecond in a 4-millisecond cycle:
- Duty cycle = on-time ÷ cycle time × 100%.
- Duty cycle = 1 ÷ 4 × 100% = 0.25 × 100% = 25%.
- Off-time = cycle time − on-time = 4 − 1 = 3 milliseconds.
These are assumed timing inputs, not a product specification or a claim that perceived brightness equals the duty-cycle percentage.
On an addressable strip, the pixel electronics perform PWM internally from a data signal. A non-addressable strip instead requires an external PWM controller, as explained by Wikipedia's LED strip guide and illustrated in Adafruit's analog RGB usage guide. Decide which control method you need before selecting a controller.
Which should you choose: RGB, RGBW or tunable white?
Choose the strip by the behavior you want along its length and the white-light channels you need. According to Wikipedia's LED strip classification, non-addressable RGB changes the whole strip together, while addressable RGB supports individual LED control.
The same Wikipedia classification describes these options:
| Desired result | Strip type | What distinguishes it |
|---|---|---|
| A uniform changing color along the strip | Non-addressable RGB | Red, green and blue channels change together across the strip |
| Chasing effects or different colors along the strip | Addressable RGB | Individual LEDs have their own control chip |
| RGB effects plus a separate white emitter | RGBW | RGB plus white: 4 chips per module |
| RGB effects plus adjustable warm/cool white | RGBCCT or RGBWW | RGB plus tunable white: 5 chips per module |
| Adjustable white without RGB effects | Dynamic tunable white | Alternating warm and cool white LEDs |
Chip counts in this table are not connector-pin counts. Use the table to choose the light functions, then match the controller to the actual strip.
White appearance and color rendering also need separate consideration. According to Wikipedia's LED article, phosphor-free multicolor LEDs have poor color rendering because their emitters are narrowband sources. A mixture that looks white therefore does not establish how faithfully it renders objects. A dedicated white channel is a feature to compare, not proof of a particular color-rendering score.
Use the color temperature guide to compare warm and cool white choices. Color temperature, measured in kelvin, describes white-light appearance; it is a different selection question from whether you want individually controlled colors.
What voltage and current does a color-changing strip need?
Match the supply voltage to the strip, then calculate current from the load. Wikipedia's LED strip guide identifies 12 V and 24 V DC as common strip voltages and 5 V for USB strips. According to the WorldSemi datasheet, the WS2812B is a 5 V example; addressability alone does not tell you which supply to choose.
Worked example: assumed analog RGB installation
According to Adafruit's analog-strip usage example, its example strip draws about 0.2 A per channel per meter, giving up to 1 A per channel over 5 m. Treat that as an example for that strip, not a universal RGB rating.
For this calculation, the assumed inputs are a 5 m analog RGB strip, a 12 V supply, and 0.2 A per channel per meter with all 3 channels fully on, adopting Adafruit's example current:
- Channel current = length × current per channel per meter = 5 × 0.2 = 1 A.
- Total current = channel count × channel current = 3 × 1 = 3 A.
- Strip power = voltage × current = 12 × 3 = 36 W.
- Power per meter = total power ÷ length = 36 ÷ 5 = 7.2 W/m.
- Cross-check current = power ÷ voltage = 36 ÷ 12 = 3 A.
The LED strip calculator uses power per meter × length and power ÷ voltage. Its supply-sizing method uses 20% headroom as the calculator's planning figure, then rounds power upward to the next 10 W:
- Headroom multiplier = 1 + 20 ÷ 100 = 1.2.
- Power with headroom = 36 × 1.2 = 43.2 W.
- Rounded supply power = ceiling(43.2 ÷ 10) × 10 = ceiling(4.32) × 10 = 5 × 10 = 50 W.
This applies the calculator's sizing formula to the assumed load; it does not establish the consumption of an unspecified strip. Use the actual strip's load rating when replacing these inputs.
What must match between the strip and controller?
Match the control method, shared-terminal arrangement and current capacity. Adafruit's example analog strip uses common-anode RGB LEDs, meaning the positive side is shared; see its strip overview.
Use this selection checklist:
- Control method: choose external PWM for a non-addressable strip or a compatible data controller for an addressable strip, following the distinction in Wikipedia's strip guide.
- Shared terminal: common anode means shared positive terminals; common cathode means shared negative terminals, as defined in Wikipedia's display explanation. Match the strip and controller arrangement.
- Channel current: compare each channel's load with its controller rating. According to Adafruit's usage guide, its analog-strip example needs power transistors or MOSFETs rather than direct drive from microcontroller pins.
For mains-voltage supply connections or changes to fixed wiring, use a qualified electrician. The calculations above concern the low-voltage load and are not mains wiring instructions.
FAQ
Can every RGB strip show several colors at once?
No. According to Wikipedia's strip classification, non-addressable RGB shows the same color along the strip; addressable RGB controls individual LEDs for spatial color effects.
Can RGB make white without a white LED?
Yes: according to Wikipedia's RGB explanation, full equal channel intensities produce white in the additive model. However, Wikipedia's LED article notes the poor color rendering of phosphor-free multicolor LEDs, so white appearance alone is not a color-quality rating.
Is RGBW the same as tunable white?
No. According to Wikipedia's strip guide, RGBW adds a single white channel to RGB, while RGBCCT or RGBWW combines RGB with tunable white. Choose according to whether you need a separate white output or adjustable warm/cool white.
Does an addressable strip need an external PWM dimmer?
Its LEDs perform PWM internally from the data signal, according to Wikipedia's strip guide. Select the compatible data controller rather than treating it as an analog strip with external channel dimming.
Can a microcontroller pin power an analog RGB strip directly?
For Adafruit's analog-strip example, no: its usage guide calls for power transistors or MOSFETs to handle the strip current. The control signal and the strip's load current are separate design requirements.
Jack Shi
Founder & editor, LEDaskJack Shi builds and writes LEDask, an independent LED-lighting tools project operated by clooms. He designs the calculators, checks their formulas and reference values against published engineering data, and writes the guides across the site.
