It is a complete computer. It just drops the case, screen and keyboard, leaving only the board in the middle.
It's called a Raspberry Pi. The name doesn't matter. What matters is it's a real computer, not a toy. It has everything a computer needs; it's just small, slow and cheap.
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How is it different from the one on your desk?
YOUR LAPTOP
Fast and pricey, switched off after use
Hundreds to thousands of dollars. It's quick, but you wouldn't leave it on 24 hours a day. It guzzles power, it makes noise, and you only have one, so tying it up gets in the way.
THIS BOARD
Slow and cheap, can stay on forever
A few tens of dollars, power use about like a phone charger, no fan so no noise. It really is slow, but the job isn't heavy anyway: it watches over one small thing, all year without a shutdown.
In short: one is your workhorse, the other is a helper you hired who never clocks out.
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It has one extra thing
That row of little pins along the edge of the board? The computer on your desk doesn't have one.
Those pins let you wire straight out to switches, lights and sensors. In other words: it can touch real things, not just stuff on a screen.
It plugs into the worldRun one wire, and the other end can be a lamp, a switch or a thermometer.
No babysittingIt does the job on time by itself. Nobody has to remember, nobody has to press anything. That is its real value.
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How to get it going
1. Load a cardTake the kind of memory card a phone uses, write the "operating system" onto it from your computer, and slot it back into the board. This is like giving it a brain.
2. Plug in powerThere is no power button. Power on means switched on. This is one of the biggest differences from a normal computer.
3. Add a screen, or skip itYou can attach a monitor and use it like a computer. More often you attach nothing, tuck it in a corner, and check on it from your own computer or phone when needed.
4. Hand it one jobThen forget about it. Its whole life is doing one small thing, forever.
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What people use it for
Block ads at homeEvery device's internet passes through it first, and the ads just vanish
Smart-ify an old TVPlug it in and pick what to watch, no new TV needed
Watch the home or shopAttach a camera and see how things are even when you're away
Water plantsWhen the soil is dry it turns on the water, so you can leave for two weeks without asking anyone
A home storage boxKeep photos and files on it. They're in your house, not in someone else's hands
Learn on itIt was built in the first place so kids could learn by tinkering
What they share: all small jobs, but all needing someone on watch constantly, exactly the kind of work people hate doing.
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What does it cost?
$50 to start
The board itself is a few tens of dollars, plus a power cable and a memory card.
No screen or keyboard to buy: just connect from the computer you already have.
How cheap is it? If you break it, fry it or wear it out, you won't cry. That alone changes whether a lot of people are willing to try.
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What it's bad at
Don't use it as your main computerIt's slow. A pile of web pages makes it choke, and forget about video editing or gaming.
The memory card wears out. With constant reading and writing, it may die in a year or two. So don't keep anything important only on it; back it up somewhere else.
And power. It has no battery, so unplug it and it stops. It starts again by itself when power returns, but whatever it was doing was cut off. For truly important jobs, plan for power cuts.
It is good at one thing: one small job, done tirelessly.
So what is it, really?
A helper that costs a few tens of dollars, sips power, and can stay on forever. Hand it a small job that needs watching every day, and you never have to think about that job again.
