I have the following target to achieve and want to know what kind of circuit that I can use? Anything that can be purchased in the market directly is preferred. Thank you!
Personally I use ESP8266 or ESP32 modules for this because they are very inexpensive and you don't need an app on the phone, they can publish their own web page with your sensor information in it. If you link them to a Wifi router you can also make the link work over the internet so the phone doesn't have to be in close proximity.
Hi KlausST, if I decide to use a prox sensor to connect to a HC-05 module +Arduino like this https://create.arduino.cc/projecthub/electropeak/getting-started-with-hc-05-bluetooth-module-arduino-e0ca81, how can I find the reference design to start to let HC-05 transmitted the detected information from prox sensor to the smartphone? I am very new to Arduino and do not know what I can play with by adding new components to the existing design.
I want to know in addition to that design, if I add a prox sensor circuit to output "1" or "0", how can I connect it to the Arduino and modifying the firmware, thus the BLE can output a control signal to tell the app what is the signal generated by this prox sensor. I only know some hardware and do not know what can I start to modify the Arduino code.