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IR sensing to detect insects
2

IR sensing to detect insects

IR sensing to detect insects

(OP)
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.

RE: IR sensing to detect insects

Wow that is a tall order as they will dissipate their heat so fast as to appear to be the same temperature as their environment.

If I were you I would start by asking IR imaging companies about if their product X can do this.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: IR sensing to detect insects

(OP)
Sorry for the confusion.  I'm not trying to detect the insect body heat.  I want to detect when an insect crosses an IR beam.

RE: IR sensing to detect insects

Is this for school?

TTFN



RE: IR sensing to detect insects

(OP)
This isn't a school project.  The device will be used to study insect behavior for genetics research.  I need to determine if the insects are moving past a specific point.  I want to sense this movement with an IR beam.

RE: IR sensing to detect insects

You might try a slottted opto-switch. This will do the job for you provided the gap is reasonable and not svereal centimetres.

RE: IR sensing to detect insects

Sean:
Please read my FAQ and give us some DATA.
The task is trivial but you have to define it with NUMBERS

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

RE: IR sensing to detect insects

(OP)
Thanks for the reply, Nick.  Here it goes.  The insect is Drosophila Melanogaster which is quite small.  The fly is confined in a 5mm OD (3.18mm ID) glass tube.  I need to detect the fly as it passes a specific point inside the tube.  Each time the fly passes the point, a microcontroller will record an activity count.  The movement will need to be detected in both light and dark situations.  Absolute darkness is required in dark stuations; not kind of dark or dark enough.  Eventually I will want to monitor up to 50 flies at the same time, each in their own tubes.  Right now I would be happy to monitor just one.  I hope this information better explains what I'm trying to do.  Thanks again.

RE: IR sensing to detect insects

The sensor is easy .
Do you know if the D. is blind for IR ?
May the range of motion limited in vertical direction?
How much positional accuracy do you need?
Can you build the circuit if you get the schematics?
How intensive is the "light situation"? May the
light be fluorescent tube ?( No IR !)






 

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

RE: IR sensing to detect insects

From what you've stated, you should be able to do this with a photo-interrupter type switch. These devices have an emitter, and detector in one package with a slot between them. By selecting the right component, you may be able to drop the glass tube in the slot. These slots are made for cogged wheels or sliding tabs for mechanical control (your computer printer or photocopier uses them).

A quick check of some stocking parts distrubitors uncovered devices like (example): Fairchild Semiconductor H22A4
http://www.fairchildsemi.com/pf/H2/H22A4.html  I'm not saying this is the one, just an example.

Check part distributors like www.digikey.com, www.mouser, www.newark.com, www.jameco.com. Use search terms like "opto switch" "Photo interrupter", etc.  These sites will have links back to manufacturers data sheets. Then check the manufacturers web sites for applications notes which will give example circuits.

RE: IR sensing to detect insects

I'd consider one emitter and two small detectors side by side.  You never know, the body parts may transmit light fairly well or not block enough.  A differential detector may be a lot more predictable.

RE: IR sensing to detect insects

It's likely that such wee little bugs won't properly block the IR with a plain-Jane off-the-shelf photo-interrupter switch tossed around the glass tube. The bugs are almost certainly too small (2mm ?) to block the beam, and also possibly too transparent.

Those sort of switches are probably designed for something large and solid to block the IR. I wouldn't even assume that they could be reliably adjusted to work (adjusted perhaps, but reliably maybe not).

Also, the glass tube might bring some optical complications. If the IR beam were very narrow, then the tube simplifies into two walls (optically simple). I think most such sensors have larger beam widths.

I don't think it is necessarily as simple a problem as simply using an off-the-shelf photo-interrupter switch. It might be, but perhaps not. Small beam width would help.

If the problem was lab rats in a 10-cm tube, then it really would be easy. But tiny bugs in a 3.18mm ID tube brings a few complications (or at least design risks).

And 'nbucska' had a VERY good (biology) question about the bugs' opinion about 'absolute darkness' versus being blasted with near IR. Camcorders pick-up near IR so it isn't a stretch to wonder about the wee little bugs needing sunglasses.

If you do use optical sensing, maybe it needs to go end-to-end through the length of the tube (with entrance and exit ports for the bugs). Might require custom circuits to be reliable. I'm assuming the bugs have better IR blockage lengthwise. Plus the signal would be longer duration.

Alternate concepts:

Maybe the bugs could walk across a microphone element ('scratch scratch scratch'). Would require a sensitive element, a low noise preamplifer, and a quiet environment. Could use multiple elements and timing/logic to reject ambient noise and determine direction.

Maybe a (very very) sensitive balance (using mass). Tricky.

Maybe ultrasonic Doppler (affect the bugs?).

Maybe vision systems (IR again).


RE: IR sensing to detect insects

Just make each bug carry a pass key.


Actually I agree with VE1BLL on the run-of-the-mill interrupter switches being iffy.

1) I would design an analog system that essentially looks for a 'dip' in the light as this would allow a fly to walk thru anywhere, upside down, etc and a dip would still occur.

2) I would put two sensors right next to each other and look for the one-two punch,(dip-dip),to confirm Mr. Bugs passage.

3) Consider using reflective technology so the light shines against the bug body and the reflected light confirms bug passage.

4) If any kind of daylight can get anywhere near this system then modulation is absolutely required if you want reliability. With the reflective system you just look on the receiver for the modulation signal to appear,(=bug).

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: IR sensing to detect insects

You want a photo- interrupter that does NOT have a Schmitt trigger in its output, so you can detect small changes in photocurrent to deal with small targets that are probably not opaque to IR.  The beam of a typical interrupter is about 1mm diameter; the tube will distort it a little, probably in a way that works in your favor.

You'll probably also need to adjust the source current.  I'd start at a couple of milliamperes and work up slowly from there.

Daylight and incandescent lights will blind the sensor, fluorescent lights won't.  I like the idea of modulating the source and just looking for that frequency on the receiver.  You don't need a fancy tuned circuit in the receiver to implement synchrnonous detection, since you've got the modulation signal a few cm away already.

Find a friend who can explain 'synchronous detection' in English and you've got your circuit designer.



Mike Halloran
Pembroke Pines, FL, USA

RE: IR sensing to detect insects

It's not that hard, an interrupter with transistor output ac coupled to an opamp then onto AD input of the micro through low pass CR filter. Drive the led with PWM, self adjusting the duty to give you a fixed level at AD input. Insect will chage the level allowing you to count it.

RE: IR sensing to detect insects

OperaHouse's differential detector is a good suggestion.

 

RE: IR sensing to detect insects

(OP)
Nick,

1. Do you know if the D. is blind for IR ?

IR is used with the flies in similar applications and there is no report that it has any effect on them.

2. May the range of motion limited in vertical direction?

The tubes will be horizontal.  They are about 70mm in length.  The fly can walk around freely inside the tube.  There is no room for it to fly.

3. How much positional accuracy do you need?

Not much is needed.  The idea is to see if the fly is moving.  It doesn't need to be monitored in an exact location.  If it moves close to the detection zone and then turns around but is detected, that is good.

4. Can you build the circuit if you get the schematics?

Yes. I should be able to build it with schematics.

5. How intensive is the "light situation"? May the
light be fluorescent tube ?( No IR !)

I'm told the light cycle does use fluorescent tubes.  I'm also told that similar devices use IR detection in the presence of fluorescent light.  Based on what you and a couple of other replies mentioned, this should not be the case!  Am I getting incorrect information from the fly people?  The flies are in a temperature regulated incubator so I'm sure the fluorescent lights are correct.  Is there a way to use IR detection in fluorescent light?

Thanks to everyone for the advice.

RE: IR sensing to detect insects

The modulation is certainly good advice -- it simplifies
the detection but complicates the circuitry.

If you want to detect the motion -- any motion --
perhaps video camera would be better.

Use -- perhaps vacuum-formed -- mini-Petri- dishes
arranged in an 8 x 8 matrix or it may even be one piece.

the video signal is digitized and iinterface to a PC. The
PC stores the picture in an array form, compares it with
the previous picture pixel -to pixel, and if there
is/isn't any difference, determines its position by cell
number.

You need a cheapest camera and inteface card, off the
shelf, no circuit to build. The software is trivially
simple.

 

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

RE: IR sensing to detect insects

But he want the system to also work in the absolute dark. So the camera would need to be IR and he'd use IR illumination (assuming the bugs are blind to IR).


I'm amazed that nobody has wandered by and suggested RFID tags...  winky smile

RE: IR sensing to detect insects

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

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

RE: IR sensing to detect insects

(OP)
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.

RE: IR sensing to detect insects

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

RE: IR sensing to detect insects

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.

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

RE: IR sensing to detect insects

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.

RE: IR sensing to detect insects

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

RE: IR sensing to detect insects

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.

"Art without engineering is dreaming; Engineering without art is calculating."
Steven K. Roberts, Technomad
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

RE: IR sensing to detect insects

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.


RE: IR sensing to detect insects

(OP)
Thanks to everyone for the input.

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