Help needed into building a special type of proximity sensor...

currently i am working on my final project for my study as an industrial designer. at the moment i am developing a product which will need to be triggered and activated by the motion of human hands. the product looks like a simple 6 inch cube which permanently rests on one side. the top side is reserved for other interaction. so what i am dealing with are the 4 remaining sides which surround the cube. the idea is that the closer a moving object [in this case a human hand or body] comes to one of the sides, the brighter the LEDs become. the range of this should be about 0 to 10 inches. the LEDs are not a problem, i just need a sensor that gives me a analog signal i can work with. and preferably this sensor will be behind a layer of around 0.2 inches of plastic material. does anyone know how this can be done? i just can't seem to find the right thing for my project. i heard an ultrasonic sensor might do the trick...but will that work stuffed away behind plastic? this would be great help for me, because i do not have a lot of knowledge on electronics to figure this out on my own. so anyone out there who can help me: i am on my knees right now hoping for a solution...any ideas will do!

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LasVegas10 years ago
Since your going for the LED to get brighter as the hand gets closer, ultrasonic would probably be the way to go. This wouldn't be very easy though. You could also go with IR, measuring how intense the signal received is to guess to proximity. To improve sensitivity for this I would place the IR receiver in a shielded tube, surrounded by perhaps 5 IR LEDs pointing straight out. As the hand approaches, more of the light from the IR's would reach the receiver and could be measured. If you were to sequence the LEDs, you could even calculate the general direction the hand was approaching from. The more LEDs, the more accurate the direction detection.
igod (author)  LasVegas10 years ago
thanks for the info. but i have one question; is it possible to hide all of these sensors behind a 5mm layer of plastic and still make them operate? because nothing can portrude trhough its outer surface [due to certain esthetical issues]...
LasVegas igod10 years ago
No problem at all! If you're using the IR technique, just place a sheet of dark red plastic in front of it. The tube surrounding the IR receiver should run up against the plastic. The IR LEDs providing the signal will then only supply reflected light to the receiver.
cocoliso31610 years ago
If you are trying rto build up a proximity sensor, you should look www.wiring.org.co he has built an open source programming environment and electronics i/o board, that would make you easier to build the proximity sensor. Or also try looking for Arduino, that does almost the same thing.
Yup10 years ago
I'd try to look into capacitive sensing. While I'm not an expert, I have seen some very cool non- contact human machine interfaces created using the technology. I'm also pretty sure that the sensing is very reliable and very cheap. I did a quick search to find the following link. good luck with the project

i dont know if this would be practical, but a magnetic proximety switch can easally be purchased over the internet, then modded so that when a hand wearing a magnetic wristband came close to it it would go off......m it might work, idunno though cause i havent seen the context that it is being used in.
igod (author)  In The House Of Ill Repute10 years ago
hmm, that would be a problem cause: 1) i do not want users to wear a special wrist band when they want to be able to interact with my product and 2) a very powerful magnet is already positioned inside, though shielded, it will still mess up the sensor thanks for the reply though ;)