Hectic Feedback!

Part of the AirGrip project is to create a pair of gloves, namely the HUMAN GLOVE and the ROBOT GLOVE. The 'human glove' sends signals to the user via haptic feedback while the 'robot glove' contains sensors that can detect obstacles. We have actually made this one of our sub-projects (one of the three). Read more about the division of the project in a earlier post: link. 

Last Friday we took apart old mobile phones to locate its vibrational motors (link) to be tested as haptic feedback.  Unfortunately we were not so lucky with it. But that didn't stop us there!

After browsing through some websites, we've found some online shops who sells vibration motors ranging from 1.5V to 10V! We have also found that piezoelectric speakers, at an optimum frequency are a plausible alternative. 

First we have the Eccentric Rotating Mass (ERM) Vibration Motors. Below is an example of one such product call 'pico vibe' by Precision Microdrives. Images taken from: link

The same online store also stocks Linear Resonant Actuators (LRA) Vibration Motors. We are actually in the process of ordering one of these to test out how suitable it is for our glove. More specifically, the Precision Haptic 10mm Linear Resonant Actuator - 3.6mm type: link. 

Lets take a look whats INSIDE a LRA vibration motor. Image taken from: link

Before our sample arrives, we have been playing around with the Piezoelectric speakers. At around 150hz and supply voltage higher than 3V, we can generate a low frequency buzzing noise but also felt on the finger! We broke the cover to isolate the piezo from the plastic casing. 

We used an Arduino to generate a square wave at a specific frequency with the 'tone()' function which also allows us to control multiple Piezos. One advantage was the low current and low power usage. However, the vibrations was weak but strong enough to 'feel' and know that it is there. 

So we have to decide... LRAs or Piezos! 

Stay tuned ... for the verdict!