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I'm trying to generate a perceptible vibration (as felt against skin) in a roughly 4x4mm area. What's the most power-efficient way to do that?

DNS
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    One common way is a small motor with an unbalanced weight in the shaft, similarly to cellphone vibrators. You may be able to generate some vibration with piezoelectric actuators too, but I'm not sure about the efficiency – clabacchio Jun 15 '12 at 13:48
  • @m.Alin: uhm....at a very low frequency maybe...but if it has an internal oscillation it would have to be tweaked to go to sub-30 Hz – clabacchio Jun 15 '12 at 13:55
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    Gentlemen, do you have any guesses as to what this target 4x4mm area might be? [Sorry, I couldn't resist.] – Nick Alexeev Jun 16 '12 at 01:35
  • Wrist, actually :P – DNS Jun 16 '12 at 01:55
  • have you tested the mobile phone's vibrator motor? – pylover Jun 21 '12 at 20:04

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This is generally known as "haptic feedback" and you may find some useful info by Googling that. As regards power efficiency, Maxim produce a piezo driver chip for this type of device and their application note discusses power consumption for a few different mechanisms. Most of the devices I've seen use those small unbalanced motors, but if you need to keep the size down to 4mm square, piezo might be the way to go.

Eddie
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A cell phone vibrating motor seems to be exactly what you want. It is designed to be felt against the skin, which is what you are also trying to do. There are many of these things out there. Jameco, for example, has quite a selection. Here is a link to just one of these so you get the idea: https://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_256322_-1

Olin Lathrop
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