This week, our group was asked to measure the power consumption of an output device. We connected a small DC motor (with a max voltage of 9 V) to a variable power supply in the Charlotte Latin School Fab Lab and determined the effect of voltage and current on power.

Before starting our investigation, we all agreed that there is a direct correlation between voltage and current. Since this is true, power must also have a direct correlation with voltage/current. The following video shows how we tested the power of the small DC motor. The variable that we decided to control was the voltage (in Volts), and we felt that it would be ideal to start the voltage at 0.1 volts and read the current (in Amps) and the power (in Watts).

Voltage, Current and Power of a DC Motor

Voltage (V) Current (A) Power (W)
0.13 0.062 0.0
0.24 0.148 0.0
0.34 0.060 0.0
0.44 0.065 0.0
0.52 0.068 0.0
0.69 0.075 0.0
0.78 0.081 0.0
0.84 0.082 0.0
0.90 0.085 0.0
1.03 0.090 0.0
1.15 0.099 0.1
2.14 0.160 0.3
3.08 0.231 0.65
4.16 0.312 1.2
5.01 0.396 1.9

In this data we collected, the motor did not have enough power to cause the central axis to spin until we got the voltage to ~0.33V. The values in the second row are in bold because the current value seems to be an outlier. We assumed the current at that voltage value should have been around 0.059 A. If this is the case, then the current reading at 0.13 V might be slightly higher (according to our data).

The power values for the majority of the tests read “0”, but we knew there were power values and the variable power supply was not registering them that low. All of the power values have an asterisk by them in the following data table because we calculated them. The following data table and graph more effectively show the effect of voltage and current on power.

We further determined the linear correlations between voltage and current and voltage/current and power.