eli5 what goes on inside your phone when it vibrates
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There’s a tiny motor inside that spins. One side usually has slightly more weight, causing it to wobble as it spins, which creates the vibration.
The ‘vibrator’ on a phone is a small electric motor with an off-axis weight attached to the rotor. When it spins, the unbalanced shaft causes it to vibrate. The whole thing is about the size of a dime.
there are different ways how phone can do it.. simplest way is electric engine with half circle spinner, that is off balance
smaller way is by using coil and metal rod that oscillates… iphone taptic engine works like that
[tiny electric motor.](https://i5.walmartimages.com/asr/577f3f21-4f5d-4a78-8b8f-02d08106398d.ddf5a3db4c7a5b232e5f20eb9bf4458d.jpeg) the shaft of the motor that spins has a weight on it. it’s attached lopsided, so it wobbles around when it spins, causing vibrations
newer phones like iPhones, have a [transducer](https://youtu.be/Nz3Z2XQZpJs?t=75). it’s like if you took a speaker and removed the speaker cone (the part that moves the air to make sound waves). instead, the vibrations are transferred into the phone, so you can “feel” the vibrations. it’s a little more complicated than that, but for ELI5, close enough
Inside the phone is a small, spinny bit. Instead of being perfect, it wobbles a little, but really really fast.
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There’s a small motor with unbalanced weights hooked in its axis, so when it’s running it causes the vibration effect
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There are 2 possible ways:
The first way is a tiny motor that spins a tiny weight around. It is similar to why a car engine vibrates when it’s running. There are a lot of spinning parts and they are not perfectly balanced and so you feel the vibration. The vibration motor and weight in your phone are purposely designed to be unbalanced in order to generate more vibration. The name of this is an eccentric rotating mass (ERM). Eccentric=unbalanced
The second method is more common in newer phones. It works using a tiny metal weight with an electric coil wrapped around it. When electricity is run through the coil the weight moves towards one side, and when the electricity is run in reverse the weight moves towards the opposite side. The electricity is flipped back forth really really fast and that moves the weight back and forth really really fast and that is what you are feeling. This is called an linear resonant actuator (LRA). Linear=the weight moves back and forth in a line instead of rotating like in a ERM
The LRA is the same concept as a speaker. In a speaker the coil moves a cone back and forth which then moves the air and makes sound. It is also the same way a doorbell works. In a doorbell the coil pushes the weight into a bell to make the ding.
There are two same-but-different technologies that can cause a vibration: A rotational motor, or a transducer. They both operate on the same principle: electricity in a coil makes a magnetic field and that field causes a force on a magnet that causes motion: The motor rotates and the transducer moves in a straight line.
A motor will convert electrical energy into a spinning motion. If you attach an off-center weight to the motor, as it spins it will vibrate. In the motor electricity passes through a coil of wire that creates a magnetic field, and that field acts on a permanent magnet to create torque. The torque makes the shaft spin and you get a vibration. The motor takes time to build up speed and thus can only ever ‘vibrate’ with multiple oscillations by the time power is applied and removed.
The second is a transducer (generic term for anything that converts energy from one form to another), but instead of causing a spin like the motor, it operates more like a speaker with a coil and a magnet on a spring. The coil can nudge the magnet one direction or the other…but instead of being attached to a diaphragm to move air to make sound like a speaker, it just vibrates the mass of the magnet around. The advantage of this method is it can create more nuanced sensations like taps or various frequency sounds. Apple calls their implementation a “taptic engine”, where the vibrations can simulate a clicking switch. Because the mass on the transducer acts nearly instantaneously, and doesn’t need to keep spinning (because it hits the end of travel causing a tap/click) it can create single pulses of motion.
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