RPM Meter with Hall Effect Square Encoder Sensors

KY-035

ATmega32U4

DSO138

Dual H-Bridge motor drivers L293D

ST7735

SN74LS14N

Neodymium magnets

General Purpose Quad Op-Amp

Arduino IDE

This project consists of using Hall effect sensors to determine the turning direction and RPMs of a DC motor. In this case 2 motors at the same time.With the use of external interruptions, the state of the sensors 1 of each pair is determined, and with this the state of the sensors 2 placed at four (90 degrees) is registered and by means of the code determine if the direction of rotation of each motor. In addition to internal interruptions (Timer1), the period time is calculated to determine the frequency (Turns per second) and the RPM of each motor.On each motor shaft, I have improvised an encoder with neodymium magnets.To control the direction of rotation of each motor, I use op amps (LM324N) with a joystick and a driver (L293N and L298N).To digitize the analog signal from each sensor I use op amps as comparators.Last but not least, I have used a Schmitt Trigger Inverter (SN74LS14N) to nullify the transient effect of each sensor, thus avoiding false readings and thus obtaining with sufficient precision the revolutions and direction of rotation of each motor.I use the ATmega32u4 (Beatle BadUSB) microcontroller as Arduino Leonardo, however the code is usable on most types of arduino.The display is a ST7735 of 128x128 pixels with SPI bus, easy to use.In the following video you can see the operation and testing of the code:<pre ><code >/* RPM Meter Direction Use Square Encoder with Hall effect sensors By DrakerDG (c) https://www.youtube.com/user/DrakerDG */ #include <SPI.h> #include <TFT_ST7735.h> #include <SimplyAtomic.h> #include <TimerOne.h> #define\t GREEN 0x07E0 #define YELLOW 0x07FF #define DC A0 //9 #define RS A1 //10 #define CS A2 //11 // Sensor pins const byte PinX[4] = {2, 3, 10, 11}; // Limit of microseconds const long uSeg = 100000; // Left position RPM labels const byte x1 = 75; // Pulse timer counters volatile unsigned long pwc[2]; // PWM periods volatile unsigned long pwm[2]; // RPM values unsigned long rpm[2]; // States of the second sensors volatile bool Sen[2]; // Count variable printing millis unsigned long prT = 0; TFT_ST7735 tft = TFT_ST7735(CS, DC, RS); void CountSA(void); void CountSB(void); void RPMc(void); void Draw_Table(void); void Print_Data(void); void setup(){ Serial.begin(9600); tft.begin(); tft.setRotation(1); tft.clearScreen(); tft.setTextWrap(true); tft.setTextColor(YELLOW, BLACK); tft.setCursor(0, 0); Draw_Table(); for (byte i=0; i<4; i++){ pinMode(PinX[i], INPUT); } for (byte i=0; i<2; i++){ pwc[i] = uSeg; pwm[i] = uSeg; rpm[i] = 0; } // Interrupt to count period time Timer1.initialize(100); Timer1.attachInterrupt(RPMc); // Interrupt of Sensor 1 of Motor A attachInterrupt(digitalPinToInterrupt(PinX[0]), CountSA, FALLING); // Interrupt of Sensor 1 of Motor B attachInterrupt(digitalPinToInterrupt(PinX[1]), CountSB, FALLING); } void loop(){ Print_Data(); } void CountSA(){ // 2nd sensor value Sen[0] = 1 & (PINB >> 7); pwm[0] = pwc[0]; // Save the period pwc[0] = 0; // Reset the timer } void CountSB(){ // 2nd sensor value Sen[1] = 1 & (PINB >> 6); pwm[1] = pwc[1]; // Save the period pwc[1] = 0; // Reset the timer } void RPMc(){ for (byte i=0; i<2; i++){ // Increase the time counter pwc[i]++; if (pwc[i] > (uSeg)){ // Limit the timer & period pwc[i] = uSeg; pwm[i] = uSeg; } } } void Draw_Table(){ // Code to draw the table on screen tft.drawFastVLine(22, 0, 128, WHITE); for ( int i=0; i<11; i+=1 ){ tft.drawFastHLine( 20, 5+i*12, 4, WHITE); if (!(i&1)){ tft.setCursor( 0, i*12 + 2); tft.print((10.0-i)*0.5, 1); } } tft.drawFastHLine( 20, 125, 128, WHITE); tft.setTextSize(1); tft.setCursor(x1, 10); tft.print("Motor A"); tft.setCursor(x1+30, 45); tft.print("RPM"); tft.setCursor(x1, 70); tft.print("Motor B"); tft.setCursor(x1+30, 105); tft.print("RPM"); tft.setTextSize(2); } void Print_Data(){ unsigned long nwT = millis(); // Calculations and prints every 10ms if ((nwT - prT) > 10){ prT = nwT; char sRPM[10]; for (byte i=0; i<2; i++){ //RPM tft.setCursor(x1, 25+60*i); // Protects math calculation ATOMIC() { // Detect Rotation Decrease if (pwc[i]>(pwm[i]*2)){ pwm[i] *= 2; pwm[i] = constrain(pwm[i], 0, uSeg); pwc[i] = pwc[i]*2; } /* detects or not the rotation of the motors */ if (pwm[i] < uSeg) rpm[i] = 6*uSeg/pwm[i]; // Detects rotation else if ((rpm[i] > 0)&&(pwm[i] == uSeg)) rpm[i] = int(rpm[i]/2); // No rotatiom // Limits the value of RPMs rpm[i] = constrain(rpm[i], 0, 9999); } dtostrf(rpm[i], 4, 0, sRPM); // Print the RPMs tft.print(sRPM); int valX = rpm[i]*120/500; // Prints the RPM bars tft.fillRect(30+15*i, 0, 10, 125 - valX, BLACK); tft.fillRect(30+15*i, 125 - valX, 10, valX, GREEN); tft.setCursor(x1-15, 25+60*i); /* Determines the direction of rotation of the motors. Prints + if it turns CW and - if it turns CCW */ if ((rpm[i] == 0)&&(pwm[i] == uSeg)) tft.print(" "); else if (Sen[i]) tft.print("-"); else tft.print("+"); } } } </code></pre><div class="se-component se-video-container __se__float-none" contenteditable="false" style="width: 100%;"><figure style="width: 100%; height: 56.25%; padding-bottom: 56.25%; margin: 0px;"><iframe frameborder="0" allowfullscreen="" src="https://www.youtube.com/embed/lOM5GylRBGY" data-proportion="true" data-percentage="100%,56.25%" data-size="100%,56.25%" data-align="none" style="width: 100%; height: 100%;" data-index="0" data-file-size="0" data-origin="100%,56.25%"></iframe><figcaption contenteditable="true"><div>Video of the tests</div></figcaption></figure></div><figure><img src=https://projects.arduinocontent.cc/f96a28a1-2ce9-4046-8f0a-53cb0f1cc7d3.jpg /><figcaption> Two Hall effect sensors placed in quadrature</figcaption></figure><figure><img src=https://projects.arduinocontent.cc/08d235f3-5377-4b76-a381-d5b532cffbfb.jpg /><figcaption> Quadruple operational amplifier (LM324N) to digitalize the analog signal of each sensor</figcaption></figure><figure><img src=https://projects.arduinocontent.cc/b641961b-3257-4177-87e9-9fb70c867cb6.jpg /><figcaption>Quadruple operational amplifier (LM324N) to control the movement of the motors</figcaption></figure><figure><img src=https://projects.arduinocontent.cc/5b3044c4-a993-4b2c-aa0b-23328420b740.jpg /><figcaption>Driever to control the two motors (L293N)</figcaption></figure><figure><img src=https://projects.arduinocontent.cc/11744d0b-7ba1-40d8-b8ab-ee578e7bb784.jpg /><figcaption>Direction of rotation indicator (+/-) and RPM of the two DC motors</figcaption></figure>

Schematic diagram of the circuit used

RPM_Meter_Direction_V3

RPM Meter with Hall Effect Square Encoder Sensors

With KY-035 quadrature sensors, the direction of rotation and the RPM of the motors can be determined.