Hi everyone! I developed keen interest in electronics and my inability to find information is really bothering me. I have this little project that I wanted to build. Its a diary which I can only open if my wireless key is in proximity. I would like to know whats the technical name for this sensor and wireless key.

Maybe a good way of starting is to ask what kind of signal is used for this? I thought initially its Bluetooth but I've seen this design with little thin key chains so maybe that could be too big for it. Anyways if if someone could give me some insight into how this sensor works I would be grateful. Please keep in mind I'm a novice at this and so far I have made a LED lamp and a simple Servo lock.

 

First decide if you want it to be like a smart key for a car, where you literally only need to be in proximity. Or if you want it like a dumb key fob, where you have to press a button on the transmitter for the diary to unlock. I think choice B might be easier since you can get most of the necessary parts basically ready to go, off the shelf in the form of an ASK radio and receiver, such as this (RF) or this (part 1 and part 2 assemble it yourself IR).

If you want to go the proximity route, then you'll need something low energy for battery life, such as Bluetooth. You'll need to handle pairing, to be sure you're talking to the correct device, and you can use RSSI pin on the receiver to estimate distance. Or if your transmitter is low enough power, then you can just assume that receiving a signal at all means you're in close enough proximity to unlock.

Someone else might have better ideas, but these are my initial thoughts.