i'm not sure i understand entirely, but i must say, those led's won't
be so visible in daylight. they'll be great indoors during daylight, or
in any non-direct sunlight application.
as for the camera.... essentially all ccd and cmos camera sensors are
sensitive to IR but almost always have a filter to block ir spectrum.
if you open a webcam and remove the blocking filter (a piece of glass
or plastic) then your camera can see IR. Some camera's are manufactured
in a way that might break your camera when you pop these parts apart
though, so you may want to google about your specific webcam and this
procedure. I use Point Grey Firefly's for such a purpose, they are
great cameras and the manufacturer makes it really easy to mess with
inline filters. only catch, these are expensive cameras, but the upside
is that they are super solid and the drivers are awesome, lots of
access to settings and everythings exposed in the sdk. one more detail
to be aware of is that the sensitivity of different ccd and cmos
sensors to different parts of light spectrum will vary and usually have
some falloff. the closer you are to visible spectrum, the more likely
your ir lightsource will be super bright.
if you would also like to block visible light but allow IR through, i
like midwest-optics, thats where i get my filters from, great company.
if you want to DIY it on the cheap, the plastic inside a floppy disk
does a fine job. rip open an old floppy and cut the black plastic to
your need. ir will pass through, visible light will be blocked. instant
night vision camera.
On Mon, 16 Jul 2012 09:44:51 -0700 (PDT), Sameer
Hello everyone. I'm very new to EE and circuits so please excuse
the stupid questions.
I'm trying to build a high-intensity IR source and test the ability of
an IR camera to track that IR source in different environments. Perhaps
I'll attach a gimbal that will move the camera around to track the IR
LED source. I am thinking I will use these LEDs I found at Adafruit:
and I've been googling around to figure out how to control and power
the LEDs and I'm somewhat lost. It appears that some recommend using an
LM317 constant-current source so that I can feed the LED with 1A. (I
plan on using the Arduino to cycle the LED on/off so I can get maximum
brightness at its peak 1A rather than limiting the current to the
constant 100 mA that it is rated for.. I'd cycle the LEDs on/off at a
rate of 33ms on/33ms off so with a 30fps camera I'd see one frame
on/one frame off. My theory is also that cycling it in this way will
help me distinguish my signal from ambient/background IR.. particularly
Adafruit's page however suggests the MOSFET:
It appears that the constant-current source would be relatively easy
where I would use the arduino to control a transistor which switches my
power connected to the INPUT of the LM317 and a resistor across OUTPUT
and ADJUST to fix the output current to 1A. However I don't know how I
would use the MOSFET to power the LED.
Also, I am wondering about where one can find an IR camera that I can
connect to my PC so I can process the IR feed with OpenCV? Ideally I
could get a setup which has a filter on it so that it could be
specifically tuned to look for the frequency of the IR LED. (940nm)
Thanks for your help.
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