Why does the Raspberry Pi not have a power button?

Question

If you buy a computer you expect it to come with a power button. So why does the Raspberry Pi not have one? Is it because it would take up too much room or be awkward to fit on the PCB?

Personally the lack of a power button is something which has always slightly irritated me, because to fully shut down the Pi you have to pull the power cable out. And I'm sure I am not the only one who has plugged in the Pi and it has started up without you wanting it to. I feel like a power button would save the hassle of having to pull the power cable out or switching off the power at the mains.

Phlip · Accepted Answer · 2015-06-16T16:13:01.993

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Modern power buttons use the Advanced Configuration and Power Interface (ACPI) to request the OS to turn its motherboard off. That's why, for a couple decades now, if you really want the motherboard off and the OS refuses, you had to mash its power button for several seconds.

A simple power switch, like a light switch, could de-power the CPU just when it's doing something important, or when virtual files are changed, and the OS needs to write them to the SD card.

So if the Raspberry went with a cheap on-off switch, more people would use it wrong and get in trouble. And adding the full ACPI harness to the motherboard would naturally make it more expensive.

I always issue sudo shutdown from inside a Pi, and give it a moment to collect its thoughts, before yanking its power. (And you should never power off by yanking the tiny, fragile MicroUSB plug from the Pi. I try to always power off using a power strip's switch, or by unplugging the distal end of the USB power wire.)

Finally, there's the slight matter that many RPIs are simply never turned off. (-;

edited Jun 16 '15 at 16:13

answered Jun 13 '15 at 16:19

Phlip

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For four seconds, not five. – Ruslan Jun 14 '15 at 08:45
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@Ruslan for three full seconds actually, it would turn off on fourth. – Gufran Jun 14 '15 at 10:57
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+1 for the never turning off thing. I think the people using a PI as a replacement for a home computer are by far in the minority vs those that use it to provide some kind of service or operate other devices. – Cubic Jun 14 '15 at 22:05
Single-letter typo: than->that. – TRiG Jun 15 '15 at 11:36
Additionally, it's really easy to setup a power switch circuit yourself that (for power off), will issue the sudo shutdown command and then wait long enough before cutting the power. – XNargaHuntress Jun 15 '15 at 13:35
i originally estimated 5 seconds. Appears it's 3 seconds for the button to engage electrically, 1 second for the OS to respond internally, and 1 second to depower peripherals. And to @XGundam05 do you have a hat example? A single power switch would make a great hat! – Phlip Jul 03 '15 at 11:49
@Phlip I do not currently have a hat example. But that would indeed make a pretty good hat! – XNargaHuntress Jul 06 '15 at 11:59
I'm not convinced by these arguments. "A simple power switch could de-power the CPU ...". So could pulling the power cable out, so that possibility still exists. "More people would use it wrong". It's an educational device, so people learning how to use it (correctly) is the main point of its existence. Why hold their hand on this issue and not others? – JBentley May 03 '17 at 22:22

score 12 · Answer 2 · answered Jun 13 '15 at 15:43

It's NOT an "end-consumer" device, like an Apple TV or a DVR or a microwave. By analogy

If you buy a car you expect it to come with door locks...

Yes, but you know the manufacturer does not provide those for free, which is why specific price tags are attached to specific goods. If I buy a car chassis, I may not expect locks. Of course, most people do not do this. But to reiterate "it's not an end-consumer device", it is not something most people would have any desire or interest in owning. Which "not most people" != "no one at all".

There's obviously some marketing philosophy going on. Like, for every feature that adds $1-2 to production costs, how is net sales going to be affected? Will we sell more because of the feature, or less because of the increased price? It is easy to say, "This will only add $0.50," but also easy to see there is a potentially very long list of things about which that might be said.

So what do the potential customers want to pay for, and what not? If there were a power button I guess that would be nice, but to be honest I could care less.

There's also a related issue, the more bells and whistles you add the more complex something is. This makes it more likely to break, in whole or part, and more difficult to debug when unforeseen problems arise.

score 8 · Answer 3 · answered Jun 14 '15 at 06:52

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A power button adds hardware / firmware / PCB space / development cost

For a budget computer, I suspect cost was the main reason why the PI didn't include a power switch.

answered Jun 14 '15 at 06:52

reggie

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score 8 · Answer 4 · answered Jun 14 '15 at 10:00

To add to the other answers:

Rasperry Pis are often used in embedded applications. In an embedded scenario, a power button is a liability, not an asset, especially if the computer is located somewhere that is difficult to access. A power switch adds the possibility that the unit will get accidentally turned off, or that it won't power on as soon as power is applied.

score 5 · Answer 5 · answered Jun 15 '15 at 01:15

If you buy a computer you expect it to come with a power button

In the case of embedded technology, that's not really true. You expect to have to yank out the power cable if you want to power down the item. There is simply no need for the complexity or physical footprint of a separate power button.

score 3 · Answer 6 · edited Jun 15 '15 at 00:43

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The similarly inexpensive Beaglebone Black has a multifunction momentary power button that uses the Power management integrated circuit (PMIC). So it was really just a trade off to avoid a few cents for the switch vs. other functionality for the same cost/PCB area.

edited Jun 15 '15 at 00:43

Basil Bourque

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answered Jun 14 '15 at 17:31

Spehro Pefhany

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An Rpi clone, the Banana Pi, also has a power button. Works as expected. – Klaatu von Schlacker Jun 14 '15 at 19:30
But if I am not mistaken the Pi does not even have a cute PMIC? – Ghanima Jun 14 '15 at 21:37

score 2 · Answer 7 · answered Jun 16 '15 at 22:13

Actually, most computers (and TVs for that matter) do not have a power button they have a 'shut down' button. If you want to power off you have to remove the cable from all of these devices.

The Pi is not so different.

And +1 for not turning them off - I don't shut mine down for days/weeks/months

Why does the Raspberry Pi not have a power button?

7 Answers7