I have an idea for a project where the arduino will know if the user is in a particular proximity (10-15ft radius) from any angle. The idea is to have a small device (size of a small thumb drive or smaller) that emits something that the arduino can detect. Perhaps it emits some type of radio data that the arduino can read a decide if it is the correct user. The could be multiple users, each with their own key device. Each user's arduino would only detect their specific key. Okay it might detect their key but it won't be the right kind of data or code or whatever.
I really have just started this project and haven't put much thought into it. I kind of wanted to see if anybody had any ideas or thoughts before I began my research.
I really have just started this project and haven't put much thought into it. I kind of wanted to see if anybody had any ideas or thoughts before I began my research.
Many seem to have asked for something like that lately, but I've yet to see a good practical solution. It's much harder then you might imagine.
Most robot designs looking for obstacle avoidance use ultrasonic ranging sensors or just one on a rotating mount to measure the closest obstacle in a given direction.
There are two ways to use wireless that I can think of, to detect proximity.
One is to send an rf signal from your base to the user, and when the user detects it, they send a signal back. You measure the time between sending the request and receiving the reply, and subtract the reaction time of the user, and divide that by two. That is how long it took your message to get from here to there. Now, all you need to do is divide that by the speed of light, and you have the distance. Of course in order for this to be useful, it needs to be highly accurate. 15 feet is about 5 meters, and the speed of light is pretty close to 300,000,000 meters per second, so it should take about 17 ns. The Arduino would be hard pressed to be that accurate. Maybe with some external hardware, though...
That system would work better with sound, or ultrasound, since it travels slower and you wouldn't have to be quite so accurate. However, I'm not sure your transducers would fit into the thumb drive size you require.
The other way is to put a crappy antenna on it (or reduce the power output) so that it can only reliably send data up to 15 feet. Then send a recognizable pattern, and when the receiver starts getting most or all of the bits right, you're getting close.
I like that last idea. I now have purchased a Blue SMIRF Silver and almost have it working. I just need to figure out how to get it connecting to the mobile device. Any suggestions as to what to do?