ir sensor grid used in touchless key pad project help

[rashidme]

Hello,

I am working on a project where I will be designing a touchless keypad. I am thinking of using a grid of ir sensors as shown in the attached pic. I tried using ultrasonic sensor but ultrasonic signal spreads out and is not good here.

So i think ir will be a good choice since ir rays travel in a straight line, correct me if i am wrong. So the idea is when the user breaks Tx_1 & Tx_2 ray, that will be a number 1, and so on and so forth.

So my questions:
1. Does ir signal/ray travel in a straight line as i have drawn in the pic with red color.
2. Do i need to amplify the transmit signal before sending it? And same for the receive signal, does it need to be amplified?


Thank you for your help.

 

[rashidme]

***bump***

 

[peufeu]

Yes IR travels in a straight line, but it can bounce off many surfaces. Also watch the beam angle of your emitters and detectors.

 

[rashidme]

To control the beam angle i can use some kind of shielding around the emitter/detector right?
and do you guys think it is a good project idea?

thanks.

 

[peufeu]

Nowadays an IR camera costs so little that the "high tech" solution would be to create a "slab" of IR light (using lots of diodes) and a camera looking at the fingers illuminated by it. This needs some complex software though.

For the beam angle you can put the emitters and detectors in little tubes, to make sure each detector only sees its own emitter. Make sure the detectors don't see the sun or anything in direct sunlight, and use pulsed IR to get rid of ambient light.

 

[rashidme]

thank you for your response. well yea the camera technique is hard to implement in software and that would be useful where one has to track finger motion or something. for our purpose we are using a simple keypad but which you don't have to touch.

 

[Dr_Doggy]

TechEBlog » LED Touch Sensor

 

[rashidme]

thats really nice!. but in our project the user is not required to touch the keypad. It can be very helpful in industrial places where a touch screen can get dirty.