10. Output Devices: Kathryn, Amalia, Jenna¶
Overview¶
This week’s assignment was to measure the power consumption of an output device. We decided to measure the power consumption of a servo from my individual assignment work.
Measuring Voltage¶
In order to find Power, I needed to first find voltage and current and use the formula Power(W) = Voltage(V) * Current (A). I used a multimeter with the dial positioned at the first option (other than OFF). I had the COM port (the black one) plugged into COM and the red plug on VΩHz.
Below is a picture of how I measured it on the multimeter.
I measured the voltage to be around 3.3V, which adds up because the servo is powered on the 3.3V pin.
Measuring Current¶
To measure current, I turned the dial to the second to last node (excluding NCV Live). I kept the black plug where it was on COM and moved the red plug to mA to measure current.
While I was measuring, I noticed that the current value began at 0.230 mA and decreased, slowing down as it did. Below is a video of the decrease.
Here are also some photos of how the value kept on getting smaller and smaller. The longest I waited was until it got to 188 mA (that took around 40 seconds) and I’m sure it would have kept on going.
I learned that it was normal for current to not be constant, but it did complicate my calculation.
Calculating Power¶
For my first calculation, I used the peak current, 0.230 mA.
Power(W) = Voltage(V) * Current (A) Using the values we found, it becomes Power= 3.3V * 0.230A (230mA)= 0.759 watts
I did another one averaging the range of values I observed.
Average Current= (230+188)/2=209 Power= 3.3V * 0.209A= 0.690 watts