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Week 11 - Output devices

Assignment

Measure the power consumption of an output device

How to measure the power consumption

Since we don’t have access to our lab because of the Covid-19 we looked into three methods of measuring the current:

  1. Use a multimeter (in Amp setting) in series with the project

  2. Use a multimeter (in Voltage setting) and use an one ohm resistor in series and measure the voltage over the resistor

  3. Use an arduino to measure voltage and use a one ohm resistor in series and measure the voltage over the resistor

Since we had no 1 ohm resistor, we tested with a multimeter in Amps settings. We used two output devices, a 28byj-48 stepper motor and an SSD1306 128x64 OLED.


Output device 1. Stepper motor

First, we connected a stepper motor to a stepper motor driver and an Arduino board. Then, we connected a multimeter between 5V power source and the motor in series like the photo below.

The current measured when the motor was running on its maximum speed was 184.4mA. The voltage was 5V, so we could calculate that the power was 5V * 0.1844A = 0.922W.

P= V * I = 5v * 0.1844A = 0.922W


Output device 2. SSD1306 128x64 OLED

We used the SSD1306 128x64 OLED display and the example code from the Adafruit library. After downloading the libraries, these can be found at File > Example > Adafruit SSD1306 >128x64 i2C.

This file runs with images of different size and varying brightness, so current varied while the code was running, and the multimeter displayed readings of between 3mA and 14mA.

P= V * I = 5v * 0.003A = 0.015W

P= V * I = 5v * 0.014A = 0.21W