Achieve vibrations controlled by audio content

Hi,

I am making small prototypes trying out different solutions for an art installation. I would very much appreciate some help in finding a good way of creating vibrations that appear linked with audio.

I aim for /haptic/ feedback when a person touches different plates. When touching each plate the person controls pitch frequency content and/or rhythmical texture of an audio stream. The haptic feedback should feel connected to the sound but does not have to be in synk with pitch frequency.

One way of solving it could be by using small dc motors with weights attached. I have tried it out a bit and it seems vaguely promising.

I use a Nano to communicate serial data over USB to audio software (PureData). The sound is controlled through analog inputs. Then I will translate the audio stream(s) to serial data and send this to the Nano output pins (digital or PWM).

What approach for controlling the motors could work? The goal is to achieve sense of connection between the sound and the touched object.

Thanks in advance!

There exist ready made vibration motors (in different sizes - it's what makes your phone buzz), indeed with a weight off centre. Those are usually regular brushed DC motors and can be controlled through a MOSFET and a PWM signal. Very simple. Change PWM duty cycle to change the speed the motors run, and with it the vibration intensity and frequency.

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wvmarle:
There exist ready made vibration motors (in different sizes - it's what makes your phone buzz), indeed with a weight off centre. Those are usually regular brushed DC motors and can be controlled through a MOSFET and a PWM signal. Very simple. Change PWM duty cycle to change the speed the motors run, and with it the vibration intensity and frequency.

Thanks, then it seems I am on the right path. What type of MOSFET would be suitable?

Assuming this are small motors just about any logic level MOSFET will do. Like the IRL540, IRLZ44N, and hundreds of others. Possibly even a simple BJT like the BC547 is enough.

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There are two main types of vibra motors for mobile phones - Eccentric Rotating Mass, (a tiny DC motor with an off-centre lump on the shaft) and Linear Resonant Actuator (a tiny speaker mechanism with a spring and a mass)

An ERM can driven fairly simply with a single MOSFET, but an LRA requires a bridge.

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Have a look at this

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Here comes some assumptions and questions, please correct me!

Another way to do vibrations is by just using a speaker hack like this:


and this must in essence be equivalent to the LRA vibration motor type.

With the battery example above you loose half the movement of the cone by using dc and not ac, but it still works. This way one could actually get by with just using a MOSFET combined with an external dc power supply. Right?

But if one would like to use ac it could become as complicated as in my thread about switching on and off an audio signal

Maybe I should I just make some hack to have the cone pulled back all the way when receiving no current. Would this make sense in order to get more movement (as in more power)?

Could this be used to give the hacked speaker +/- movement?

Then you would need to apply more power to overcome the force pulling back to cone. There is no magic available to help.
Paul

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