power

All Raspberry Pi models have a few built-in LEDs; the earlier models had PWR, ACT, and networking status LEDs all lined up on the board itself; for the B+ and model 2 B, the networking LEDs moved onto the network jack itself, leaving just two LEDs; PWR (a red LED) and ACT (a green LED).

Normally, whenever the Pi is powered on—except if the power supply dips below something like 4.5VDC—the red PWR LED remains lit no matter what. If you wanted to 'disable' the LED, you'd have to put a piece of tape or something else over the LED, or get out a soldering iron and modify the hardware a bit.

Raspberry Pi model 2 B, B+ and A+ (and beyond)

Luckily, with the Pi 2 model B, B+, A+, and Zero, you can control the LEDs in software, in a few different ways. The simplest way to change the way these LEDs work is to modify the trigger for each LED by setting it in /sys/class/leds/led[LED_ID]/trigger, where you replace [LED_ID] with 0 for the green ACT LED, and 1 for the red PWR LED.

For example:

This morning, our beloved electrical power was gone at the seminary (apparently it left us at 4:50 a.m.). Needless to say, there was much confusion for some time. But, in the end, everyone set up flashlights so we could see while getting ready for the day, and we found that ol’ St. Nicholas had remembered not only candy in our shoes, but also a bright, red candle for ever-needed morning light. The electrical power returned just before we began morning prayer, and now we are back online and operational.

This made me think about things in chapel (where we each were holding one or two candles to read our books for morning prayer). What is power? What is our ‘guiding light’? Who controls it? Surely we lowly humans, sinners that we are, do not control our power—we are shown this in many ways, the least of which being the power outages such as the one this morning. In our society, being without electrical power degrades our feeling of power. But who gives us any power we may have? God. We must remember that all of our modern conveniences are given to us by God through the work His creation, men.