9. Output Devices¶

Task¶

Measure the power consumption of an output device

Development¶

We decided to compare the power consumption of two devices: a simple red LED and a small pololu geared motor.

Red LED¶

We calculated the power consumption of the LED setup from last week.

Last week we measured a voltage drop across the LED of 2.07V with a current of 4mA. Therefore, the LEDs power consumption is:

P = I*V = .004 * 2.07 = 8.28mW

Pololu geared motor¶

There is plenty of information in the brand’s page about the wide variety of motors. We assumed it’s a 12V one.

At 6V we counted around 150 rpm, unloaded. It drew 0.02A. At 12V it drew 0.03A. Can’t really say much about the relative increase since its in the lower bound of out sensitivity: we might be getting these readings with anything between .15 to .24 and .25 to .34, so the range is wide.

P = I*V = 20mA * 6V = 120mW

P = I*V = 30mA * 12V = 360mW

Loaded close to stall (by hand):

P = I*V = 120mA * 6V = 720mW

P = I*V = 200mA * 12V = 2400mW

12V loaded

It could be felt getting hotter.