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
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