Community Earth

Sunday, 31 May, 2009 § Leave a comment

Well after a long period of development and testing I together with icube and nuigroup are rolling out RC1 of Community Earth for the community to start getting involved in development and give feedback on the project.

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Bi-Directional LED Sensing Tips

Friday, 22 May, 2009 § 10 Comments

Okay since my last post i’ve been doing a bit of reading and doing some tests on bi-directional led sensing. These are a some Tips i present to people who are interested in taking this further. I personally have given up perusing this route of sensing mainly due to its limitations of use, and sensing capabilities.

Helpful Hints

Helpful Hint #1: Using Inexpensive LEDs as Optical Sensors

Most LEDs can be used as detectors without harming the device in any manner, there are some leds which dont work as well, the ideal typle of led is a red led and with a clear casing.

The trick to get an led to sense is to electrically bias the LED in the proper current-voltage (I-V) quadrant for operation as a detector and to detect an appropriate range of wavelengths.

The LED, as the name (Light Emitting Diode) implies, is electrically a diode and can be used as a detection device similar to a photodiode.

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LED Sensing

Sunday, 3 May, 2009 § 3 Comments

Alrite to update from my previous post heres an update video of my 3×2 matrix using led sensing

LED Sensing ~ Bi-Directional LEDs – Part 2

Sunday, 3 May, 2009 § Leave a comment

So to continue on with my last post … Now that we have this photo current what can we do with it, how can we make use of it, to detect inputs. The nature the LED is such that the photo current is very small, due to the geometry of the PN junction, which is not designed to maximise to act as a photo diode. However using a small trick we can integrate all photo currents over a set period of time, and make the diode act as a capacitor.  We  this by charging up the diode  and then seeing how long it takes the photo current to discharge and go to a logic zero.

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LED Sensing ~ BI-Directional LEDs Part – I

Sunday, 3 May, 2009 § Leave a comment

In my quest to find other methods of input detection for multi-touch and multi-modal hardware i came across another technique made famous by Jeff Han it is the use of LED s as bi-directional sensors. This technique is in no means new, it know fact that LED s can behave in such a way that, they act as sensors, when they are reverse biased. The theory behind how this all works is explained below.

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