Output Devices¶
Measuring the Power Consumption of an Output Device¶
This week we had to measure the power consumption of an output device for our group assignment.
Measuring an NeoPixel LED¶
For this assignment, we measured the power consumption of a WS2812b RGB LED strip with 10 individually addressable LEDs. The strip was controlled using an Arduino, and each LED was lit up in various colors and brightness levels to observe how this affected current draw.
Setup¶
- Device: WS2812b (NeoPixel) LED strip
- Number of LEDs: 10
- Microcontroller: Arduino
- Power Supply: 5V
- Measurement Tool: In-line ampere meter
What is an In-Line Meter?¶
An in-line meter is a tool placed directly between the power supply and the device. It measures real-time voltage, current, and power consumption. It is useful for quickly observing how changes in a circuit (like different LED colors) impact power usage. In our setup, the meter was connected between the power source and the Arduino.
LED Color Sequence¶
The Arduino code cycles through the following colors on all 10 LEDs:
- Red (255, 0, 0)
- Green (0, 255, 0)
- Blue (0, 0, 255)
- Gray (100, 100, 100)
- Light Gray (150, 150, 150)
- Lighter Gray (200, 200, 200)
- White (255, 255, 255)
Each color is displayed for 3 seconds, with a short animation effect between each LED.
You can download our code for the measurement here.
Measuring Instantaneous Power and Power Consumption¶
To calculate the power usage at each color state, we used the formula:
Power (W) = Voltage (V) × Current (A)
Energy (Ws) = Power (W) * Time (s) (Power Consumption over time (Energy consumed))
The following table shows the approximate measurements from the in-line meter during each color phase:
| Color | RGB Value | Current (A) | Voltage (V) | Power (W) | Time (s) | Power Consumption (Ws) (1Ws = 1/3600 Wh) |
|---|---|---|---|---|---|---|
| Green | (0, 255, 0) | 0.241 | 5.00 | 1,205 | 3 | 3,615 |
| Blue | (0, 0, 255) | 0.240 | 5.00 | 1,2 | 3 | 3,6 |
| Gray 100 | (100, 100, 100) | 0.261 | 5.00 | 1,305 | 3 | 3,915 |
| Gray 150 | (150, 150, 150) | 0.331 | 5.00 | 1,655 | 3 | 4,965 |
| Gray 200 | (200, 200, 200) | 0.401 | 5.00 | 2,005 | 3 | 6,015 |
| White (Full) | (255, 255, 255) | 0.481 | 5.00 | 2,405 | 3 | 7,215 |
| Red | (255, 0, 0) | 0.240 | 5.00 | 1,2 | 3 | 3,6 |
Observation and Analysis¶
From the measurement data, we observe that the basic colors Red, Green, and Blue each consume approximately the same amount of current – around 0.240 A. This indicates that when only one LED channel (R, G, or B) is active, the power draw remains moderate.
However, as we start combining these channels to create more complex colors (e.g., different shades of gray and white), the current draw increases significantly:
- Gray colors are composed of equal parts red, green, and blue at varying intensities. As the intensity increases (e.g., from RGB (100,100,100) to (200,200,200)), the current draw also rises.
- White light (RGB 255,255,255) requires all three LED channels to be at full brightness. This results in the highest measured current at 0.481 A, nearly double that of a single-color state.
Similarly, as the current increases with the brightness and combination of color channels, the required power consumption in watts also rises, ranging from 1.2 W for single colors up to 2.405 W for full white.
This clearly shows that power consumption scales with the number of active color channels and their intensity, making full white the most power-intensive state.
Conclusion¶
The experiment clearly shows that brighter colors and more active RGB channels lead to higher power consumption. White, which uses all three RGB channels at full intensity, results in the highest current draw.
By using an in-line meter, we were able to measure and compare the electrical characteristics of different lighting conditions.