Using a TI LM35 temperature sensor with Arduino Mega
This is some code I wrote for fun to read the temperature from a TI LM35 temperature sensor and output the result with a speaker as morse code.
Note: Fig. 7 from the LM35 datasheet seems so have a different number in the current version of the datasheet
C++
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/* * Code to monitor temperature as measured by an LM35 sensor * Connect as shown in Fig. 7 of datasheet (+Vs to 5V, GROUND to GND, Vout+ to pOut, Vout- to pVGND) * * I found one 1N4148 diode to be enough (-> raises GND by about 0.49V, so good until -49°C) * * I used a 10 kOhm resistor instead of a 18 kOhm one * * Outputs values via Serial and morses them with a speaker connected to a resistor -> pin pSpeaker and GND * * Author: Nicolai Spohrer <nicolai@xeve.de> * License: GPL v3 <http://www.gnu.org/licenses/gpl-3.0.html> */ #include <Tone.h> Tone tone1; int freqs[] = {NOTE_A4, NOTE_A5}; int DOT_LENGTH = 75; // morse dot length in ms int pOut = 2; // pin to V_OUT of LM35 int pVGND = 1; // pin to GND of LM35 (to measure raise of ground voltage by connected diodes) float REFERENCE_VOLTAGE = 2.56; // either 5.0 or 2.56 (Mega only) int pSpeaker = 13; void setup() { tone1.begin(pSpeaker); Serial.begin(9600); if(REFERENCE_VOLTAGE == 2.56) { analogReference(INTERNAL2V56); // now one ADC step is 2.56V/1024=2.5mV^=0.25°C } } void loop(){ readAndPrint(); delay(5000); } void readTemp(float &vOut, float &vVGND, float &vTemp, float &temp, float &roundTemp) { /* * vOut is output voltage of LM35 relative to Arduino ground * vVGND is "virtual" ground voltage (raised by diode) of LM35 relative to Arduino ground * vTemp is voltage difference between vVGND and vOut, ergo the actually important voltage * temp is temperature as float * roundTemp is temperature rounded to nearest 0.5 * (remember the LM35 has only 0.5°C guaranteed accuracy at +25°C) */ // 1024.0 because of 10 bit ADC resolution vOut = analogRead(pOut) * REFERENCE_VOLTAGE / 1024.0; // Vout+ in datasheet vVGND = analogRead(pVGND) * REFERENCE_VOLTAGE / 1024.0; //Vout- in datasheet vTemp = vOut - vVGND; //Vout in datasheet temp = vTemp * 100; roundTemp = round(temp * 2.0) / 2.0; // round to nearest 0.5 } void readAndPrint() { float vOut, vVGND, vTemp, temp, roundTemp; readTemp(vOut, vVGND, vTemp, temp, roundTemp); Serial.print("vOut | vVGND | vTemp | temp | roundTemp : "); Serial.print(vOut); Serial.print(" | "); Serial.print(vVGND); Serial.print(" | "); Serial.print(vTemp); Serial.print(" | "); Serial.print(temp); Serial.print(" | "); Serial.println(roundTemp); if(roundTemp < 0) { /* * If temperature is negative, morse a minus sign and continue with |temperature| */ morse('-'); roundTemp = -roundTemp; } /* * Extract the digits from the temperature reading */ byte dec1 = ((int)(roundTemp*100))%10; //5 in 123.45 byte dec0 = ((int)(roundTemp*10))%10; //4 in 123.45 byte ten0 = ((int)roundTemp % 10); // 3 in 123.45 byte ten1 = ((int)roundTemp % 100 / 10); // 2 in 123.45 byte ten2 = ((int)roundTemp/100); // alternatively, ten2 = ((int) roundTemp % 1000 / 100), but roundTemp < 1000 anyway /* * +48 to convert from byte to char */ if(ten2 != 0) { morse(ten2+48); } if(ten1 != 0) { morse(ten1+48); } morse(ten0+48); morse('.'); morse(dec0+48); morse(dec1+48); morseWordPause(); } void morse(char chr) { switch(chr) { case '0': morseLong(5); morseCharacterPause(); break; case '1': morseShort(1); morseLong(4); morseCharacterPause(); break; case '2': morseShort(2); morseLong(3); morseCharacterPause(); break; case '3': morseShort(3); morseLong(2); morseCharacterPause(); break; case '4': morseShort(4); morseLong(1); morseCharacterPause(); break; case '5': morseShort(5); morseCharacterPause(); break; case '6': morseLong(1); morseShort(4); morseCharacterPause(); break; case '7': morseLong(2); morseShort(3); morseCharacterPause(); break; case '8': morseLong(3); morseShort(2); morseCharacterPause(); break; case '9': morseLong(4); morseShort(1); morseCharacterPause(); break; case '-': morseLong(1); morseShort(4); morseLong(1); morseCharacterPause(); break; case '.': morseShort(1); morseLong(1); morseShort(1); morseLong(1); morseShort(1); morseLong(1); morseCharacterPause(); break; } } void morseLong(int times) { for(int i=0; i<times; i++) { tone1.play(freqs[0], 3*DOT_LENGTH); delay(3*DOT_LENGTH + 1*DOT_LENGTH); } } void morseShort(int times) { for(int i=0; i<times; i++) { tone1.play(freqs[0], DOT_LENGTH); delay(DOT_LENGTH + 1*DOT_LENGTH); } } void morseWordPause() { delay(7*DOT_LENGTH); } void morseCharacterPause() { delay(3*DOT_LENGTH); } |
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