IR sensing to detect insects 2

[sean001]

I am interested in detecting insect movement with an IR emitter and detector. I have no experience with designing circuitry and need a good resource that will help me understand what I need in order to make this happen. Any assistance will be appreciated.

 

[nbucska]

of course, and you can use IR LED for illumination.
The cheapest camera would be OK with a frame grabber.


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[sean001]

The camera option may not be practical. Putting the flies in the tubes is a must; there's no way around that. The immediate goal is to monitor up to 50 individual flies. Later that number will increase. There is a limited amount of space to work in. The tubes will be stacked as close as possible. I do not know how much an IR camera will cost but doubt I will have the money to buy that many of them.

Am I understanding correctly that it's impossible to do this with an IR beam in fluorescent light? The lab uses monitors that claim to be using an IR beam to detect the flies. These monitors are used in fluorescent light (or at least that's what I'm told). If someone would clarify that for me I would be grateful. Thanks.

 

[MacGyverS2000]

Would the mass of the flies be enough to alter local capacitance? What about inductance if they walked into a coil wrapped around the tube?

I don't know the answer, but wanted to throw the ideas out there for further thought. Either method would remove the need for any illumination at all (IR or otherwise), and would be impervious to any "daytime" lighting.


Dan - Owner

http://www.Hi-TecDesigns.com

 

[nbucska]

Sean:
Re cost: The camera may be the cheapest solution -
just think about the mechanical work of installing
and wiring 50 sets of LED-s,phototransistors,
circuits,computer interfaces, etc. The system would
not detect any motion but only if a D. crosses
the beam.

The tube is 5mm OD, about 3mm ID. If the D. confined
in longitudinal ( relative to the axis of the tube)
direction? Can you design a planar arrangement where
the camera can see all of the cells ?

I don't understand the limitations and without
knowing more, I don't think i can really help.



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[btrueblood]

IR thru-beam sensors typically work okay in indoor light. At most, you may need to cover the tube/sensor with a piece of electrical tape to cut down on stray light. I've only had trouble in outdoor (sunlight) and high-temperature environments, where ambient IR is high. DigiKey carries a ton of photosensors, I found several for about $2.50 each in 5mm slot versions.

 

[itsmoked]

Hi sean001,

You shouldn't have a big problem with fluorescent lights.

The key with all optical systems is Signal to Noise ratio SNR. If your IR is the dominant light, from the sensor's point of view, then it will swamp the fluorescent lighting.

Most all IR device makers recognize that the only way to deal with high dynamic light variations is thru the modulation method. Because of this all the different IR comm devices like TV, VCR, DVD, stereos, etc., use this method. In fact they all use the exact same method.(Note: Most houses now have copious fluorescent lighting) This is why all the remotes seem to understand every device out there. What you want to do is piggy back on that knowledge/functionality. You want to use the exact same scheme and modulation technique. I would look for these parts starting with STi corp. You could use for instance a remote control to send an endless stream of "TURN ON TV" or some other short command and detect the signal reflected off of the fly's body.



Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[nbucska]

50 channel demodulator/detector/interface is not a
simple/cheap circuitry.

Plesae read FAQ240-1032
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http://geocities.com/nbucska/>

 

[itsmoked]

??!!

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[MadMango]

IR cameras can be had for as little as $35USD, probably less.

What about a simple laser ($5USD with a fan-shaped beam) and a normal optical sensor. If the little bug crosses the beam, the received light will decrease and some form of software should be able to count that as a hit.

[green]"Art without engineering is dreaming; Engineering without art is calculating."[/green]
Steven K. Roberts, Technomad
Have you read faq731-376 to make the best use of Eng-Tips Forums?

 

[btrueblood]

Uh, why 50 channels of anything, if he wants to try it with one tube as a start? Scaling up: a single micro could poll up to 8 or 16 of them at once, and store the count for eventual readout. 4 to 8 micros eventually, but it's still a solution that's under $500 (assuming he does his own wiring, and using something like a Basic Stamp controller), or about $10 per bug.

 

[sean001]

Thanks to everyone for the input.