Guide
How a ring can answer with a buzz.
A buzz is the quietest answer a device can give: nobody else hears it, and you do not have to look. Whether it says anything depends on two things: the small motor that makes it, and how few, clear patterns it is asked to make.
In short. Most buzzes come from one of two tiny actuators: an eccentric rotating mass, which spins a weight, or a linear resonant actuator, which shakes a mass on a spring like a small loudspeaker. A driver chip shapes the pulses, pushes the motor to start quickly and brakes it to stop cleanly, which is what makes a pattern crisp. A few patterns you can tell apart say more than one buzz for everything.
What haptics is
Haptic feedback is information you feel: a vibration, a tap, a pattern of pulses. A small actuator inside the device shakes a tiny weight; the length, strength and rhythm of the pulses make different patterns.
The two motors behind most buzzes
- ERM, eccentric rotating mass. The original vibration motor: a small motor spins a weight that sits off its axis. Its strength is tied to its speed, so how hard it shakes and how fast cannot be set apart, and it shakes in two directions.
- LRA, linear resonant actuator. Works more like a loudspeaker than a motor: a voice coil moves a mass on a spring along one axis. It has one resonant frequency where it shakes hardest, a few hertz off it loses much of its strength, and each unit’s frequency differs slightly, so it needs a driver chip that tracks its resonance. LRAs are typical in phones and small handheld devices.
Driver chips do much of the work. Texas Instruments’ DRV2605L, for example, drives both kinds, tracks an LRA’s resonance, overdrives and brakes an ERM automatically, and ships with a licensed library of more than a hundred ready-made effects from Immersion, so a designer can choose a click or a double pulse instead of drawing waveforms.
Why crisp matters
A pattern is only as clear as its edges. In a bench test by Texas Instruments, with the same driver and a 3.6 V supply, one ERM took 47 milliseconds to start and 37 to brake, while two LRAs took 43 and 93 milliseconds to start and 17 and 24 to brake. The lesson is not that one kind always wins, but that start and stop times differ part by part, and that braking matters: a weight that keeps moving after the signal ends turns two short pulses into one long smear.
Why patterns, not just a buzz
One kind of buzz only says “something happened”, and you reach for a screen to find out what. A few patterns you can tell apart say what happened: a message from someone who matters, a yes, a no, a reminder. Fewer patterns, learned well, beat many that blur together. That is also why a device that buzzes for everything trains you to ignore it: calm technology.
Lychnos Ring’s patterns
Lychnos Ring gives its answers their own patterns: true, false and not sure each feel different, and so do a new message and a reminder. The first line of the answer is on the ring’s screen if you want it, and the rest at your ear. On a phone that vibrates, you can feel the patterns on our home page.
Where a buzz is enough
- In a meeting: “the mail you were waiting for has arrived”.
- On a walk: “turn off the oven” at the right time.
- After a question: “is that true?” answered with a yes, a no or a not sure.
More on answering without a screen in your hand: phones in meetings. Ever felt a buzz that was not there? Phantom vibrations.
Sources, read 4 November 2026: Texas Instruments, DRV2605L haptic driver and application note SLOA207, haptic implementation considerations for mobile and wearable devices (revised 2021); Precision Microdrives, vibration motors and linear resonant actuators.
Questions
What is the difference between an ERM and an LRA?
An ERM, an eccentric rotating mass, is a small motor that spins an off-centre weight, so its strength and its frequency rise and fall together. An LRA, a linear resonant actuator, moves a mass on a spring with a voice coil, much like a loudspeaker, at one resonant frequency, and needs a driver chip tuned to it. LRAs are common in phones and other small handheld devices.
Why do some vibrations feel crisp and others smeared?
Mostly because of how fast the motor starts and stops. Driver chips push a motor harder at the start and brake it at the end; without braking, the weight keeps moving after the signal ends and short pulses run together.