infinite powered device

Presenter : Karim swilam

content ❍ self powerd camera

❍ The scientific basic

❍ Is it a new idea ?

❍ Photo diode usage and mode

❍ The circuit

❍ The camera and its applications

Digital self powerd camera ❍ Shree K. Nyaar a reasearcher in Columbia University's Computer

Vision Laboratory in the US

set the prototype of a digital camera that can film for ever has been built

upon one very simple concept:

Digital cameras and solar panels

The digital camera ❍ Measures light interfernce , deflection and phase difference to create

images

The solar cell ❍ As simply known converts light to electricity , through npn semi

conductor under forward bias

❍ But they both use roughly the same technology and components

❍ Combine the two and what have you got? A perpetual recording device that doesn't require any batteries or external power supply

❍ As long as it's near a steady stream of light

combination

IS it a new idea ?

NO its not The idea has been previously raised but with few different designs

So what's new ?

The scinetists design a pixel circuit using

2 transistors and a pixel

photo diode

The photo diode Usage

❍ The photodiode is used here is switching between the two sensor functions:

❍ photovoltaic for charging up the camera which is used in solar cells too

❍ photoconductive for capturing images

when light fall on the pn junction:

If the absorption occur in :

-The depletion region

-Or 1 diffusion length away from it

The electron-hole pare are swept away from W and the photocurrent

is produced

photo current = Dark current (no light )+ photocurrent (due to photon)

when ever decreasing dark current senstivity to photons increase and

give more effecient photodiode which will give higher current and

voltage

The photo diode : ( under reversed bias)

The photo diode has two popular modes :

photovoltaic mode ( zero bias mode ) :

photovoltaic effect is the creation of voltage and current through

photoelectric phenomenon.

photoconductive mode :

at the heart of any digital camera there is an image sensor (chip with millions of pixels ) photodiode in each pixel produces an electric current when exposed to light .

which let the pixel measure the intenisty of light falling on it

The pixel circuit ❍ 2 transistors and 1 photodiode

How it works ❍ During each image capture cycle pixels are used to record and read

out the image

❍ Then save energy and charge sensor power supply

❍ so when camera isn't used to capture it can be used to charge any other device too

Applications ❍ since it's low resolution camera it can be used in security systems

or anything simple

But it has an important role that it can work for along period of time

Therefore it can be used on recording videos and images on another

planet

Thank you