I am either going to use a bluetooth shield or a wifi shield. These are the ones I'm looking at:
I chose these devices because they seemed to be the most expensive in their class. The goal is to connect a mobile device to the arduino directly and wirelessly. I want the best range I can get and I also need to be able to get signal strength data from the shield. The signal strength data will allow me to see if the connected device is far away or close up so I can perform actions based on that distance. I understand you can't really tell distance by signal strength and that's not what I'm doing. Basically, if the signal is really low I'll now that the connected device is not right next to the arduino. If the signal is really high, I'll know that it is. That's all I need from it but I DO NEED THIS DATA. Has anyone worked with any of these devices? I know the Xbee gives signal strength data but I obviously can't use Xbee for connecting to a mobile device.
Thanks so much for your help and if you have any questions just ask.
I'm sure it will. All I need to do is see what the signal strength is when the device is about 10 ft away and that will be the threshold. I don't see why that wouldn't work.
durkinnj:
I'm sure it will. All I need to do is see what the signal strength is when the device is about 10 ft away and that will be the threshold. I don't see why that wouldn't work.
A lot of things can change signal strength besides just distance.
I'm sure it won't. Strength is not a distance indicator. For example: If you a very close but inside of the quarter wavelength of the signal, it'll measure very low.
The Bluetooth devices that work with Arduino are typically serial devices. Getting sideband data is difficult since you have to escape out of "data mode" and into "command mode" (like old school modems.)
Alright. Well thank you for this information. I did not know this. This is a great explanation and it does make sense. My research was incorrect and a lot of people had false information on other forums. So with this new knowledge, it seems there is no way to sense proximity of a user with a mobile phone no matter what, wifi, bluetooth, nothing. Am I correct?
durkinnj:
it seems there is no way to sense proximity of a user with a mobile phone no matter what
Maybe it was due to an imprecise explanation, but this isn't what you originally asked. You asked about determining distance. This makes it sound like you are trying to measure distance and not detect proximity, which is different.
My research was incorrect and a lot of people had false information on other forums. So with this new knowledge, it seems there is no way to sense proximity of a user with a mobile phone no matter what, wifi, bluetooth, nothing. Am I correct?
I would love to see the forums where somebody has a successful distance measurement like you describe. Not sure why you asked here when you had apparent "true" information from other sources. If you get a reliable distance measurement system working, do post up your methods. As to proximity, if a signal is detected, the transmitter is somewhere within range. No signal, the transmitter may be in assumed range, or not.
I wish I could reference the forum where I actually found someone that provided a mathmatical formula to estimate distance based on signal strength. They were saying that it wasn't going to be accurate but it would give an approximation. That's all I needed. In fact, I don't even need that. I just need to know, is it close, or is it far away. That's it. I don't need to measure distance. I would just measure the signal strength at about 10 feet away or take an average between 10 and 15 feet see what the signal strength is and choose that as a threshold. If the signal crosses that threshold I will see it as "close" and if it is lower than that value I will see it as "far" that's it. I am not trying to measure distance in any way. Sorry if I did not make that clear. I just need a very rough proximity measurement. The reason why I came here after researching is because I could not get anything that would allow me to read the signal strength from any shield. That is my question. Is there a wifi or bluetooth shield with a long range that allows the arduino to read the signal strength information of the connection at any time.
On average, radio waves will follow the inverse square law. I suppose the person you were quoting assumed that the actual signal strength really followed this law in practice. Unfortunately it doesn't- tiny changes in the relative position of the transmitter and receiver and the environment around them can make differences that outweigh the simple effects of range.
