How embedded systems work: the hidden computers in everyday things, and how engineers build them
Sensors and actuators: how a tiny computer feels and moves the world
A microcontroller only feels tiny changes of electricity on its pins. Yet one can tell one cat from another and keep the wrong one out. Two kinds of parts let it reach the real world: sensors and actuators.
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1
Rono follows the wires from the pins. The first one runs to the reader, a ring of copper wire around the tunnel, the short passage a cat walks through.
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2
When a cat is in the tunnel, the reader sends out weak radio waves. They wake the cat's tag, which answers with its number, and the reader passes that number to the chip as an electric signal.
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3
A part that turns something of the world into a signal for the chip is a sensor. This one turns a cat into a number.
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4
The second wire goes the other way, from the chip to a small motor that moves a little bar, the latch. A part like this motor, which turns a signal from the chip into an action, is an actuator.
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5
So the flap feels the world through its sensor and moves it through its actuator. Everything is in place to stop the grey cat, but something must still decide when to open.
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Quick check
A smart night light.
Show the answer
The sensor is the part that feels the light and turns it into a signal. The actuator is the lamp, which turns the chip's signal into light in the room.
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Go further
The real names of the pins and of the radio.