Measuring resistance by phone to Android
In this application, we will measure the resistance information and send it to the Android phone via the Bluetooth module.
Resistance measurement in multimeters is actually a voltage measurement process. As can be seen in the resistant connection diagram of the Arduino, an unknown resistance connects to the circuit. The larger the value of the resistance, the greater the tension on it. The resistance value is calculated with the following codes:
Float volt_x = analogread (A0); // Vin Input
Float volt_in = 5*(volt_x/1023);
float rx = (volt_in*100000)/(5-volt_in); // ---------- >>>>>> Resistance Formula
float rx_divided = rx/1000; // ohm ----> k ohm
If the value read by the analogread command is placed in the formula, the resistance value is found.
We convert this value primarily to the type of string variable and then to the series-jar type. And with the following command line, we send a Bluetooth modular.
Flutter-Dart codes were used for the Android program. Flutter-Dart and Arduino codes below.
Flutter-Dart Codes:
import 'dart:async';
import 'dart:convert';
//import 'dart:convert';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:flutter_bluetooth_serial/flutter_bluetooth_serial.dart';
void main() => runApp(const MyApp());
class MyApp extends StatefulWidget {
const MyApp({super.key});
@override
// ignore: library_private_types_in_public_api
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
List<BluetoothDevice> _devices = [];
late BluetoothConnection connection;
String adr = "00:21:07:00:50:69"; // my bluetooth device MAC Adres
String recData = "0 ohm";
late Timer _timer;
String _timeString = "";
@override
void initState() {
// _startTimer(); automatic
super.initState();
_loadDevices();
}
Future<void> _loadDevices() async {
List<BluetoothDevice> devices = await FlutterBluetoothSerial.instance
.getBondedDevices();
setState(() {
_devices = devices;
});
}
//----------------------------
Future<void> sendData(String data) async {
data = data.trim();
try {
List<int> list = data.codeUnits;
Uint8List bytes = Uint8List.fromList(list);
connection.output.add(bytes);
await connection.output.allSent;
if (kDebugMode) {
// print('Data sent successfully');
}
} catch (e) {
//print(e.toString());
}
}
// data RECEIVED --------------
Future<void> receiveData() async {
connection.input!.listen((Uint8List data) {
//Data entry point
setState(() {
recData=ascii.decode(data);
//var n1 = int.parse('-42');
});
});
}
//--------------------------------------
// TIMER START-----------
void _startTimer() {
_timer = Timer.periodic(Duration(milliseconds: 500), (timer) {
receiveData();
});
}
// TIMER STOP--------------------------------------
Future<void> _stopTimer() async {
setState(() {
});
_timer.cancel();
}
//---------------------------------------------
@override
void dispose() {
_timer.cancel();
super.dispose();
}
@override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(
title: const Text("OHMMeter with BlueTooth"),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
const Text("MAC Adress: 00:21:07:00:50:69"),
ElevatedButton(child: Text("Connect"), onPressed: () {
connect(adr);
},),
const SizedBox(height: 30.0,),
const Text("Receive Data: ",style: TextStyle(fontSize: 55.0),),
Text(recData,style: TextStyle(fontSize: 45.0),),
const SizedBox(height: 10.0,),
// Text(_timeString),
const SizedBox(height: 10.0,),
ElevatedButton(child: Text("Stop timer"), onPressed: () {
_stopTimer();
},),
const SizedBox(height: 10.0,),
ElevatedButton(child: Text("Start timer"), onPressed: () {
_startTimer();
},),
],
),
),
)
);
}
Future connect(String address) async {
try {
connection = await BluetoothConnection.toAddress(address);
// sendData('111');
//durum="Connected to the device";
} catch (exception) {
// durum="Cannot connect, exception occured";
}
}
@override
void debugFillProperties(DiagnosticPropertiesBuilder properties) {
super.debugFillProperties(properties);
}
// --------------**************data gonder
//Future send(Uint8List data) async {
//connection.output.add(data);
// await connection.output.allSent;
// }
}
//------------*********** data gonder end
Arduino codes:
#include <SoftwareSerial.h>
SoftwareSerial mySerial(10, 11); // RX, TX
char Buf[50]; // to bluetooth device<------
String resistor_string="";
void setup() {
// hc-05 bluetooth module resistor-----------------------------
// Open serial communications and wait for port to open:
Serial.begin(9600);
mySerial.begin(9600);
}
void loop() {
float volt_x = analogRead(A0);// Vin INPUT
float volt_in=5*(volt_x/1023);
float RX=(volt_in*100000)/(5-volt_in); //------------>>>>>> resistance formula
float RX_divided=RX/1000; // ohm ----> K OHM
resistor_string=String(RX_divided);
resistor_string= resistor_string+" K ohm";
resistor_string.toCharArray(Buf, 50);
mySerial.write(Buf);
delay(200);
}
