I can’t seem to understand the engineering behind non-push buttons. Take for example my coffee maker. I tap my finger on the top of it and it turns on, but theres no physical button, just the power symbol. I figured this would be more fun than asking google.
In: 5
Basically, your finger simulates a capacitor in the circuit, and that is detected, activating the function.
Non-push buttons, also known as capacitive touch buttons, work by detecting changes in electrical capacitance. When you touch the surface of the button, you change the electrical field around it, and the button’s circuitry detects that change. This then triggers the desired action, such as turning on your coffee maker.
It’s a very low voltage current, like a signal current that passes through the button. If that signal stays the same, then the machine knows the button wasn’t touched. When your finger makes contact, it disrupts the signal (you are conductive) and the machine takes that disruption as a button push and does something. There is other circuit board logic to help determine a true button push over some sort of fault, like using the capacitance of a human finger to set a realistic range of disruption or predict how the signal will be changed accurately, and rejecting signals that don’t fit the expectation.
You have likely experienced non-push buttons more often in your recent day to day activities than not – unless you’ve never used e.g. a touchscreen phone. If you don’t question the magic of a non-deformable material *that is entirely transparent* and lets you view movies through it, why do you believe there’s something special about the button on your coffee maker?
Capacitive coupling is the general means by which these surfaces work as buttons. If you increase the capacitance between your body and the button surface, by e.g. wearing gloves, you’ll find the effect severely diminished.
> I figured this would be more fun than asking google.
🙁
Well, you have **Capacitive button** to search now at least for more reading. https://en.wikipedia.org/wiki/Capacitive_sensing
A pushbutton or any mechanical switch is pretty simple. You open or close a circuit, allowing electricity to flow. A capacitive sensor works by detecting the presence or absence of something other than air. A conceptually similar example might be a light detector that changes signal when it is covered. So when detecting that, the system then does whatever it would do if the electrical signal was changed.
The short version is that the electricity behaves differently when a water-and-salt-filled body (i.e. your finger) is at that surface.
A difference is that with a switch, you could directly send the power through, like for simple light switches. The others it’s like telling another system to throw a switch. This includes **electrical relays**, where a smaller signal operates a larger switch, but also the electronic ones.
How about when there isn’t a button? You just touch anywhere on the base and it turns on (for example, maybe not a coffeemaker but I’ve seen them on lamps, even from decades ago)
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