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I'm trying to make an item with a number of pads that will pulse individually or in sequence with a given signal. I have looked at vibration motors but these are like the ones in video game controllers - they vibrate but the duration is too long. I want to put the motor in a pad that could be worn and give a much more precise 'pulse' or 'beat', potentially at a rate of up to three times per second.

Any ideas where I can find such a motor or other feedback component?

Many thanks.

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    \$\begingroup\$ Stuart does not know which component would suit his needs, so at least that part of the question is valid for this forum. The "where can I get it most cheaply" part is probably not. \$\endgroup\$ – Wouter van Ooijen Nov 23 '12 at 17:41
  • \$\begingroup\$ How long a duration would be correct? \$\endgroup\$ – Brian Carlton Nov 26 '12 at 19:10
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You need a voice coil actuator (VCA). It is most commonly used as the active component in most loudspeakers - a coil of wire and a permanent magnet produce an excursion proportional to current. In fact, you could probably prototype your application with small, inexpensive speakers.

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Some recent mobile phones use piezo actuators, driven by dedicated haptics drivers at various voltages (50 to 200 Volts peak to peak). This provides precise vibration feedback, such as you may feel when using a Swype touchscreen keypad on some Android phones.

The advantages of these actuators:

  • Very small size and light weight for given level of vibration feedback
  • Very low power consumption compared to vibration motors
  • Extremely short start and stop times (1.5 mS) and duration resolution
  • Fine frequency control and wide frequency range: e.g. 1 Hz to 350 Hz vibration
  • No magnetic field hence no risk of erasing magnetic stripes on credit cards etc

While online stores like Digikey do not seem to have the really small haptic piezos, only their larger cousins, the piezo benders (coin piezo speakers), you could actually use a bender for your purpose. Also, I know at least one local business that hand-fabricates their own piezo haptic actuator sheets using piezo materials bought from ebay or AliExpress. It's pretty low-tech and not a recent development at all.

This article gives an outline of the various haptic feedback options commonly used, from motors to piezos.

To drive a piezo actuator, you can build an oscillator + voltage boost solution of your own, or use a highly integrated single-chip solution such as TI's DRV8662 which pretty much takes care of everything, from PWM input through to voltage boost up to 200 Volts.

One of my projects incorporated a piezo haptic feedback solution using a regular peizo coin speaker, which was acceptable because a really strong vibration was not needed, just perceivable touch notification.

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Try some sort of solenoid, or even a pulse through a small loudspeaker.

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The easiest method used by cell phones is a sub-miniature dc motor with some control over the voltage and duration in software. These vibrate silently based on an unbalanced rotor weight, but the speed or vibration is DC controlled so it is not as precise. enter image description here

For precision, use a piezo speaker. ALthough it is not silent due to harmonics, it is as precise as the wave you apply, thin and low power.

It depends on the effect you need, precise pulse rate tick sounds or precise silent vibration frequency with Morse code modulation done in software.

enter image description here

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