# 9. Output Devices - Connor and Landon¶

The assignment for this week was to measure the power consumption of an output device. The students in this group are Connor Cruz and Landon Broadwell.

## Finding Voltage and Current¶

We used a 3.3V power supply to give power to the OLED screen (and the chip that programmed it). Using Connor’s ATtiny412 board, we connected the OLED through the correct pins and power supply and measured the voltage. To measure it, we used a multimeter, changing the knob to “V” and moving the red probe to the corresponding hole. We then hooked up both probes to the power and ground, respectively, and ran a program created by Connor. What we hoped to accomplish with this program was to send multiple screens of code to the OLED rather than have it just display one message so that the voltage might vary when new messages are sent. Instead, it simply displayed a constant voltage of around 3.36V, which correlates with the 3.3V power supply.

The next test we ran was that of using the multimeter to measure current. With the help of Richard Shan, we used the mA option of the multimeter, changed the probe, and used both probes to have the current run through the multimeter. It ended up measuring around 1.70mA - 1.90mA.

## Calculating Power¶

To calculate the power consumed by the 128x64 OLED screen, we used the formula: P = VI, where P = power, V = voltage, and I = current.

Although we did not have a constant current, since we measured 0.19 mA for most of the time, we will use that value. Therefore, plugging in these values, we get:

P = 3.361 * 0.00019 = 638.59 uW

This was a very surprisingly low power to get after comparing to other groups. For example, group A got 0.5W as their total power consumption. Even if our group had used a 5V power supply, it would not come much closer to that value. This is most likely due to how group A used a servo, which is a moving component. Also, each pixel in an OLED screen is self-lit (hence the “LED” part of OLED), so there is not a need for as bright a light as other screens like LCD. The size of the screen also likely contributed to the small power consumption.

Last update: March 28, 2024