This project of mine started because I wanted to learn how to layout my own printed circuit board (PCB). I needed a simple and easy-to-solder circuit, so I chose this one because who doesn't love interactive LEDs?
In this Instructable I will only be showing the implementation of my circuit on a breadboard. In my next Instructable (now available here), I will demonstrate my process of designing and laying out the PCB.
As I mentioned I wanted a simple project and this one is just that! Students, hobbyists, and anyone else of all skill levels will be able to easily put this together. Let's get started!
This step is the "How it Works" section. If you prefer to get right into making the circuit, skip to the next step.
If you're still with me, I'm going to start with a brief introduction of some of the components I used in this circuit. (An exact list of materials is in the next step.)
So how does this all work? What makes it proximity-sensing? Remember in the explanation above that the photo-transistor acts like a switch. So when the photo-transistor is off, no current is flowing across it to our blue LED and the LED is off as well. Now look at the other side of our circuit. That's where the IR LED is connected, and it is connected such that it is always on and emitting 880nm infrared waves. Remember that I also mentioned the photo-transistor is set to respond best to wavelengths of 880nm? That's how the proximity-sensing works! When an object (such as your hand) goes over this little "cluster", IR light of 880nm is emitted from the IR LED. This light reflects off of your hand and back to the circuit. When the photo-transistor picks it up, it turns on allowing current to flow through from the source to our blue LED lighting it up!
Note: The light we're dealing with doesn't have to specifically be 880nm to for this to work. The important thing is just that the photo-transistor responds best to the wavelength of light that the IR LED emits.