I need to design a system where somebody carrying their phone goes past a sensor or something and then an app on their phone detects this and measures the time between walking past 2 of the sensors/checkpoints. I was thinking that the checkpoints would be sump5le 433MHz transmitters transmitting a constant signal, and the time at which the signal was strongest would be used by the phone. Only trouble is, most mobile phones can't pick up 433MHz. Any ideas? Thanks in advance

 

Using a cell phone for this application limits your choices and makes your project quite complicated. What is your experience level in designing electronic hardware and writing software? Once we know that we can make suitable suggestions to help you with your project. Is the project just a fleeting fancy or do you have an urgent need?
Regards,
Keith

 

Using a cell phone for this application limits your choices and makes your project quite complicated. What is your experience level in designing electronic hardware and writing software? Once we know that we can make suitable suggestions to help you with your project. Is the project just a fleeting fancy or do you have an urgent need?
Regards,
Keith

Thanks for your quick reply. I'm fairly new to electronics but I've been programming for quite a while. I was thinking I would probably write the app in dart, with flutter. I would really like to get this project to work, but if its going to be really expensive then I will have to stop. I'm perfectly happy to spend a long time on it (months and months if that's neccesary) Thanks!

 

Could your app access the microphone on the phone? Then you could have a sound which the app could detect. I have no idea whether you could use a sound of a sufficiently high or low frequency that you can't hear it, but the microphone could pick it up.

 

Could your app access the microphone on the phone? Then you could have a sound which the app could detect. I have no idea whether you could use a sound of a sufficiently high or low frequency that you can't hear it, but the microphone could pick it up.

hmmmm, that's an interesting concept. the only trouble is the phone would most likely be in a backpack, but I can do some testing to see how well it works. Thanks for the idea!