I try to make work the radioshack IR emitter/detector pair that I have bought (RS 276-0142)
I have
5V -> detector -> resistor (2k) -> ground
5V -> emitter -> resistor -> ground
The detector is also connected to an analog input to measure the voltage between its leads.
every second I print to the serial port the analog value of the voltage of the detector
I have tried many combinations (swapping detector and emitter, changing leads, ...) but the detector has always the same voltage
(around 750)
I hide it with my hand, turn on and off the lights, unplug the emitter, ... nothing. Always the same value
well this might not help much but I know that IR signals are specific signals and stuff and u should probably download the IR library. I don't know barely anything about this but u should look into how an IR receiver works. You don't just measure the voltage or resistance. It is a specific code.
You may not have enough current going thru the transmitter.
Reading the not-really useful info at the RS website one gets the impression the emitter has 1.6V forward voltage drop.
So (5v - 1.6)/2K = <2mA current flow, may be too little for the detector.
Also reading the website reviews, it is hard to say what the detector really is:
"What's in the box
1 x infrared emitter - 2V 40mA
1 x phototransistor detector - 20V 25mA"
Set up the IR emitter to pulse, and the receiver to drive an LED and see if the pulses make it thru, going down to say a 150-180 ohm resistor for more current flow.
Then go about inputting that into the arduino.
Start your work on this with a voltmeter "watching" the pin from the detector you intend to connect to the Arduino.
Watch the IR emitter through a digital camera or webcam, after trying to look at a working IR remote control... many digital cameras are sensitive to IR, and you can see it which you can't with your naked eye.
See also...
... but skip most of the stuff at the top for now... go down to the "Broken Beam Detectors" section.
I've used these - I used something like a 220 ohm for the emitter - can't recall on the detector but believe it to be in the 20k to 50k ohm range. We aware that ambient light will effect your readings and could be why our only seeing 700's readings - try the detector in the dark without the emitter - should get about 1023 - then add the emitter and see what you get.
How would one go about making a sketch using a IR detector/emitter circuit to detect eye movement?
would it concentrate on the reflectance or a difference of reflectance from two sensors? Or some sort of average reflectance?
Something that helped me : if you use a video camera (like your iPhone or equivalent), you will see the infrared light in red (I don't know why)
The infrared is only toward the up of the emitter, so the detector wasn't detecting anything.
I had to curb the detector and the emitter to point one toward the other.
I still don't know why covering the detector with my hand (to "hide" the ambiant light) didn't change the voltage. There are no IR in ambient light ?? Or do they go through skin ?
from wikipedia:
"The second broad category uses some non-contact, optical method for measuring eye motion. Light, typically infrared, is reflected from the eye and sensed by a video camera or some other specially designed optical sensor. The information is then analyzed to extract eye rotation from changes in reflections. Video based eye trackers typically use the corneal reflection (the first Purkinje image) and the center of the pupil as features to track over time. A more sensitive type of eye tracker, the dual-Purkinje eye tracker,[21] uses reflections from the front of the cornea (first Purkinje image) and the back of the lens (fourth Purkinje image) as features to track. A still more sensitive method of tracking is to image features from inside the eye, such as the retinal blood vessels, and follow these features as the eye rotates. Optical methods, particularly those based on video recording, are widely used for gaze tracking and are favored for being non-invasive and inexpensive."
How would one go about making a sketch using a IR detector/emitter circuit to detect eye movement?
One would go about it very carefully, with a very low power emitter - the eye has no blink reflex to invisible light, and retinal damage could occur.
About the only thing going for you is it won't be focussed very well.