10 - Output Devices¶
Assignment¶
Measure the power consumption of an output device.
Background: Power Consumption¶
Power consumption is the rate at which electrical energy is used, typically measured in watts (W) or kilowatts (kW).
A Watt (W) is the standard unit of power, representing the rate at which energy is consumed or produced — equivalent to 1 joule per second (J/s). It represents instantaneous work, such as electrical energy conversion.
Power Formula:
P = Vdrop * A
Power = Volts * Amps
Component Research¶
Angela created a reference table of typical power consumption ranges for components we planned to test or use in our projects. All typical ranges were researched from publicly available sources and are based on small hobby-sized components.
We did not test and calculate the power consumption of every component listed — the table serves as a reference for expected values.
| Component | Typical Power Consumption Range | Notes | Voltage Across Component | Measured Amperage | Calculated Power Consumption |
|---|---|---|---|---|---|
| Individual RGB LED | 0.1W – 0.3W | Affected by brightness and color. White is highest power consumption. | — | — | — |
| LED Strip | 7.2W – 20W | Measured per meter. Common 5050 strip is ~14W/m at full brightness. | — | — | — |
| Buzzer | 0.01W – 0.03W | Consumes very little power. Industrial buzzers can reach 1.5W. | LED Off: 0.229V / LED On: 0.232V | LED Off: 15.16mA / LED On: 15.33mA | LED Off: 0.00347W / LED On: 0.00356W |
| Speaker | 3W – 10W | Affected by volume and audio content (e.g., bass levels). | — | — | — |
| LCD Display | 0.005W – 2.5W | Varies by size, brightness, and backlighting. | — | — | — |
| OLED Display | 0.01W – 0.1W | Affected by size, brightness, contrast, and white levels. Standby can be as low as 0.005W. OLED TVs range 75W–250W. | — | — | — |
| Servo Motor | 1W – 5W | Industrial servos can reach 1000W. | — | — | — |
| Stepper Motor | 10W – 20W | For an average hobby-size motor. | — | — | — |
| 3V DC Motor | 0.18W – 1.2W | Dependent on motor size and load. Can be as high as 3000W. | 0.9V | 49.0mA | 0.0441W |
Test Boards¶
We built two breakout boards for testing output devices.
- Board 1 (Dorian) — Output: Buzzer
- Board 2 (Camille) — Output: Hobby Motor
Test 1: Buzzer (Board 1)¶
Circuit Setup¶
Dorian created a breakout board using the Seeed XIAO RP2040. The sensor, LED, and speaker are each on separate pins, so they do not affect readings taken on the speaker path.
Code¶
Dorian’s sketch plays different notes and toggles the LED based on the ambient light sensor reading. View full code and note frequency reference
How the Buzzer Works¶
This speaker uses a piezo crystal that compresses when voltage is applied, moving an attached disk to create sound. The higher the frequency of movement, the higher the pitch of the sound.
Measurements¶
We tested the current at both output notes by breaking the circuit and connecting the multimeter in series.
| State | Note | Voltage Drop | Current | Calculated Power |
|---|---|---|---|---|
| LED Off | C4 | 0.229V | 15.16mA | 0.00347W |
| LED On | C5 | 0.232V | 15.33mA | 0.00356W |
The voltage drop difference between the two notes was only 0.007V. Both readings fall well within the typical buzzer range of 0.01W–0.03W.
Test 2: Hobby Motor (Board 2)¶
Circuit Setup¶
Camille and Kim set up the motor board with a small hobby motor and fan attachment. Camille wrote the motor code; Kim reviewed it and helped get the motor spinning. The motor was powered using the 3V pin on the board.
Measurements¶
| Supplied Voltage | Measured Current | Calculated Power |
|---|---|---|
| 0.9V | 49.0mA | 0.0441W |
The calculated power falls within the typical 3V DC motor range of 0.18W–1.2W, on the lower end — consistent with a lightly loaded motor and fan attachment.
