KPM12-J High-Resolution Resistance-Based Displacement Sensor
In this video I show you another displacement sensor. The KPM12-J is a resistance-based, high-resolution displacement sensor. This makes it very simple to read it because you only need a good AD-converter.
Wiring diagram
Both the ADS1115 and the 16x2 LCD are using the i2C protocol. I did not find the model for the KPM12-J sensor, so I substituted it with a regular potentiometer. Technically, there is no difference between them from the ADC’s point of view: both are just some voltage dividers.
Arduino source code
#include <LiquidCrystal_I2C.h> #include <Wire.h> #include <Adafruit_ADS1X15.h> LiquidCrystal_I2C lcd(0x27, 16, 2); Adafruit_ADS1115 ads; int cin1; //for reading the instructions from serial int samplingfreq; //sampling frequency [milliseconds] float distance = 0; //for the calibrated distance float adcRead; //for the raw data void setup(void) { Serial.begin(115200); //some info to know what is on the Arduino Serial.println("KP12M-25mm Displacement sensor, LCD, Button."); Serial.println("Getting differential reading from AIN0 (P) and AIN1 (N)"); Serial.println("ADC Range: +/- 6.144V (1 bit = 3mV/ADS1015, 0.1875mV/ADS1115)"); // The ADC input range (or gain) can be changed via the following // functions, but be careful never to exceed VDD +0.3V max, or to // exceed the upper and lower limits if you adjust the input range! // Setting these values incorrectly may destroy your ADC! // ADS1015 ADS1115 // ------- ------- // ads.setGain(GAIN_TWOTHIRDS); // 2/3x gain +/- 6.144V 1 bit = 3mV 0.1875mV (default) // ads.setGain(GAIN_ONE); // 1x gain +/- 4.096V 1 bit = 2mV 0.125mV // ads.setGain(GAIN_TWO); // 2x gain +/- 2.048V 1 bit = 1mV 0.0625mV // ads.setGain(GAIN_FOUR); // 4x gain +/- 1.024V 1 bit = 0.5mV 0.03125mV // ads.setGain(GAIN_EIGHT); // 8x gain +/- 0.512V 1 bit = 0.25mV 0.015625mV // ads.setGain(GAIN_SIXTEEN); // 16x gain +/- 0.256V 1 bit = 0.125mV 0.0078125mV //----Set default------ ads.setDataRate(RATE_ADS1015_920SPS ); //Sampling speed ads.setGain(GAIN_TWOTHIRDS); // Gain (set to max now) ads.begin(); //-----------------Taking care of LCD------------------- //NOTE: if you cannot see the text on the LCD, try to change the potmeter on the back of it. //Sometimes you just have wrong contrast settings and nothing shows up on the screen because of it. lcd.begin(); // initialize the lcd lcd.backlight(); //initialize backlight //------------------------------------------------------ lcd.clear(); //clear the LCD lcd.setCursor(0, 0); //Defining positon to write from first row,first column . lcd.print("KP12M-25mm"); //some message lcd.setCursor(0, 1); //Cursor is moved to the 2nd line of the LCD lcd.print("Reading displ."); //You can write 16 Characters per line . delay(3000); //wait 3 sec } void loop(void) { //-------------------------------------------------------------------------------------------------------- double startTime = millis(); //define the time NOW. This will be useful when we need some time readings if (Serial.available() > 0) { char cin = Serial.read(); switch (cin) //Our usuial SWITCH-CASE method { //-------------------------Changing SPS settings--------------------------------------------------- case 'd': delay(50); while (!Serial.available()); SPSifchecker(cin1); //we change the SPS (sampling frequency) by sending and integer between 0-7 (Check the function below) //Example: the message "d 2" sets the SPS to 2 which is: 490 samples per second break; //------------------------------------------------------------------------------------------------- //-------------------------Changing PGA settings--------------------------------------------------- case 'w': delay(50); while (!Serial.available()); PGAifchecker(cin1); //we change the PGA (onboard amplifier) by sending an integer between 0-6.(Check the function below) //Example: the message "w 2" sets PGA to 2 which is: 2x gain +/- 2.048V 1 bit = 1mV 0.0625mV break; //------------------------------------------------------------------------------------------------- //--------------------------Reading data and sending to PC----------------------------------------- case 's': //s: Start while (Serial.read() != 'N') { //While we don't interrupt it by sending 'N' to the Arduino double elapsedTime = millis() - startTime; //start another timer adcRead = ads.readADC_Differential_0_1(); //read the ADC 0 and 1 pins in differential mode distance = (-0.0009353088486627 * adcRead + 27.36432542127); //calibrated displacement //------------Serial printout----------------- Serial.print(elapsedTime); //elapsed time since this part of the code is running Serial.print("\t"); //tab for separation Serial.print(adcRead, 0); // raw data, 0 decimals Serial.print("\t"); //tab for separation Serial.print(distance, 6); //calibrated data (displacement), 6 decimals Serial.print("\n"); //linebreak //------------------------------------------- delay(200); //delay 200 ms } break; //------------------------------------------------------------------------------------------------- //------------------------------------Single Readout to PC----------------------------------------- case 'r': //Read. Just a one shot reading. adcRead = ads.readADC_Differential_0_1(); //read the ADC 0 and 1 pins in differential mode distance = (-0.0009353088486627 * adcRead + 27.36432542127); //calibrated displacement //------------Serial printout----------------- Serial.print(adcRead, 0); // raw data, 0 decimals Serial.print("\t"); //tab for separation Serial.print(distance, 6); //calibrated data (displacement), 6 decimals Serial.print("\n"); //linebreak //------------------------------------------- delay(3000); //wait a bit more break; //------------------------------------------------------------------------------------------------- //------------------------------Using LCD---------------------------------------------------------- case 'l': //LCD data // we read the sampling frequency from the serial. Lower number, higher sampling rate. // this number is independent from the SPS settings. This controls the frequency of Serial.println() samplingfreq = Serial.parseInt(); while (Serial.read() != 'N') { //While we don't interrupt it by sending 'N' to the Arduino double elapsedTime = millis() - startTime; //start another timer adcRead = ads.readADC_Differential_0_1(); //read the ADC 0 and 1 pins in differential mode distance = (-0.0009353088486627 * adcRead + 27.36432542127); //calibrated displacement //------------Serial printout----------------- Serial.print(elapsedTime); //elapsed time since this part of the code is running Serial.print("\t"); //tab for separation Serial.print(adcRead, 0); // raw data, 0 decimals Serial.print("\t"); //tab for separation Serial.print(distance, 6); //calibrated data (displacement), 6 decimals Serial.print("\n"); //linebreak //------------------------------------------- //-------------LCD Printout------------------ lcd.clear(); //clear LCD lcd.setCursor(0, 0); //Defining positon to write from first row,first column . lcd.print("Displacement"); lcd.setCursor(0, 1); //Defining positon to write from second row,first column . lcd.print(distance, 6); //You can write 16 Characters per line //------------------------------------------- delay(samplingfreq); //we have to subtract the code's running time, to get the exact frequency. } break; //------------------------------------------------------------------------------------------------- default: break; } } //-------------------------------------------------------------------------------------------------------- } void PGAifchecker(int cin1) { //the commented parts are for testing, but I left them in the code cin1 = Serial.parseInt(); //Serial.println(cin1); //Serial.println("first cin"); delay(50); //Serial.println("after delay"); if (cin1 < 1 ) { ads.setGain(GAIN_TWOTHIRDS); // 2/3x gain +/- 6.144V 1 bit = 3mV 0.1875mV (default) //1 //Serial.println("test"); //Serial.println("PGA-0"); } else if (cin1 < 2) { ads.setGain(GAIN_ONE); // 1x gain +/- 4.096V 1 bit = 2mV 0.125mV // 1,5 //Serial.println("PGA-1"); } else if (cin1 < 3) { ads.setGain(GAIN_TWO); // 2x gain +/- 2.048V 1 bit = 1mV 0.0625mV // 3 //Serial.println("PGA-2"); } else if (cin1 < 4) { ads.setGain(GAIN_FOUR); // 4x gain +/- 1.024V 1 bit = 0.5mV 0.03125mV // 6 //Serial.println("PGA-3"); } else if (cin1 < 5) { ads.setGain(GAIN_EIGHT); // 8x gain +/- 0.512V 1 bit = 0.25mV 0.015625mV //12 //Serial.println("PGA-4"); } else if (cin1 < 6) { ads.setGain(GAIN_SIXTEEN); // 16x gain +/- 0.256V 1 bit = 0.125mV 0.0078125mV //24 //Serial.println("PGA-5"); } //Serial.println("The value of the PGA now is:"); //Serial.println(cin1); } void SPSifchecker(int cin1) { //the commented parts are for testing, but I left them in the code cin1 = Serial.parseInt(); //Serial.println(cin1); //Serial.println("first cin"); delay(50); //Serial.println("after delay"); // try it with == 1, without ' ' or " " if (cin1 < 1) { ads.setDataRate(RATE_ADS1015_128SPS ); // 128 samples per second //Serial.println("128 SPS"); } else if (cin1 < 2) { ads.setDataRate(RATE_ADS1015_250SPS ); // 250 samples per second } else if (cin1 < 3) { ads.setDataRate(RATE_ADS1015_490SPS ); /// 490 samples per second } else if (cin1 < 4) { ads.setDataRate(RATE_ADS1015_920SPS ); // 920 samples per second } else if (cin1 < 5) { ads.setDataRate(RATE_ADS1015_1600SPS ); // 1600 samples per second (default) } else if (cin1 < 6) { ads.setDataRate(RATE_ADS1015_2400SPS ); // 2400 samples per second //Serial.println("2400 SPS"); } else if (cin1 < 7) { ads.setDataRate(RATE_ADS1015_3300SPS ); // 3300 samples per second } //Serial.println("The value of the PGA now is:"); //Serial.println(cin1); }
