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MQ-3 Alcohol Sensor, Breakout Board + Arduino -- MQ-3 Alcohol Sensor, Breakout Board + Arduino -- Home Forum Wiki Code RSS Twitter Facebook Search Wiki Search Code -- Search Forum Search Blog Login / Register About Privacy Policy GDPR MQ-3 Alcohol Sensor, Breakout Board + Arduino Friday, October 18 th , 2013 A lot has happened since our last article was published and to celebrate the continuance of we’ll be playing with the MQ-3 Alcohol Gas Sensor . Coupled with the SparkFun Gas Sensor Breakout Board , connecting the MQ-3 to your Arduino is a breeze. The MQ-3 is a heater-driven alcohol sensor that outputs an analog signal (usually interpreted somewhere between 150 and 1023 depending on how long you let the sensor warm up), which through the use of your Arduino code and calibration, can be interpreted for whatever use you need. Putting The Pieces Together When attaching your MQ-3 to the SparkFun Breakout Board , it should be noted that it doesn’t matter which way the MQ-3 alcohol sensor is pressed in. Both the A pins are electronically the same as well as the B pins. The center pins on both sides are the heater element pins. Since the circuit will be running on +5V DC it doesn’t matter which way the sensor is soldered to the board. As long as you have the SparkFun logos and pin labels facing downward, so you can still see them when the sensor is flipped over, you are good to go! Note: Again, the MQ-3 is heater-driven so be aware that the sensor will become warm and may even emit a smell at first. This is completely normal. Calibration: If you take your time, you can find out what values equate to specific percentages or even blood alcohol concentration in the case of a breathalyzer. You will of course need to calibrate your MQ-3 based on your specific Arduino code since sensor readings will vary. Although I can’t help with your specific calibration scenario, the best advice I can give you is to use several isopropyl alcohol bottles at different percentages for your testing. Do NOT get the sensor wet with alcohol! Simply squeeze to breathe the vapors of the alcohol into the sensor and take your readings. Code The Arduino code for this is very simple if you just want to view the raw data. int mq3_analogPin = A0; // connected to the output pin of MQ3 void setup(){ Serial.begin(9600); // open serial at 9600 bps } void loop() { // give ample warmup time for readings to stabilize int mq3_value = analogRead(mq3_analogPin); Serial.println(mq3_value); delay(100); //Just here to slow down the output. } Tweet No Comments Sensing Humidity With The SHT15 + Arduino Tuesday, November 27 th , 2012 The SHT15 is a digital humidity sensor that outputs a fully calibrated humidity reading. And… because what we are measuring is actually relative humidity , and relative humidity being relative to temperature, the SHT15 has a builtin digital thermometer. This makes things much easier to work with than sensors without a thermometer onboard . You can pick one up from sparkFun here . Hooking it up The SHT15 uses a two-wire connection for communication that is similar to, but not, I2C. So we wont be able to use the Arduino’s dedicated lines for this. The down side is it is a bit slower to get readings from, the plus side is that you can connect it to any 2 digital pins you want. We are using pins 2 and 3 on our arduino. BEFORE YOU SOLDER IT UP… Note that this board can not be washed! So if you are using flux, or solder that you normally clean up, don’t (They actually recommend to use “no-clean” solder just so you don’t have to worry about it). And be extremely careful not to get it wet at all. AFTER YOU SOLDER IT UP… To get a clean reading, the sensor needs to be stored at >75% humidity for at least 12 hours to allow the polymer to re-hydrate (just what the doc says). If you don’t, your SHT15 may read an offset that slowly disappears if exposed to ambient conditions. Alternatively the re-hydration process may be performed at ambient conditions (>40% Humidity) for 5 + days. Im not exactly sure how you do that… But someone noted that they put it in a ziplock with a wet towel (not touching) for 12H. Code The code for this is a bit wacky (as with most digital sensors), but it is split up pretty nicely, and is as easy to read as it can be. Note that the readings are a bit slow to return a value (100+ ms). //Based of the wiring code at http://wiring.org.co/learning/basics/humiditytemperaturesht15.html int SHT_clockPin = 3; // pin used for clock int SHT_dataPin = 2; // pin used for data void setup(){ Serial.begin(9600); // open serial at 9600 bps } void loop(){ //these can take a bit to get the values (100ms or so) float temperature = getTemperature(); float humidity = getHumidity(); Serial.print(temperature); Serial.print(" | "); Serial.println(humidity); } float getTemperature(){ //Return Temperature in Celsius SHT_sendCommand(B00000011, SHT_dataPin, SHT_clockPin); SHT_waitForResult(SHT_dataPin); int val = SHT_getData(SHT_dataPin, SHT_clockPin); SHT_skipCrc(SHT_dataPin, SHT_clockPin); return (float)val * 0.01 - 40; //convert to celsius } float getHumidity(){ //Return Relative Humidity SHT_sendCommand(B00000101, SHT_dataPin, SHT_clockPin); SHT_waitForResult(SHT_dataPin); int val = SHT_getData(SHT_dataPin, SHT_clockPin); SHT_skipCrc(SHT_dataPin, SHT_clockPin); return -4.0 + 0.0405 * val + -0.0000028 * val * val; } void SHT_sendCommand(int command, int dataPin, int clockPin){ // send a command to the SHTx sensor // transmission start pinMode(dataPin, OUTPUT); pinMode(clockPin, OUTPUT); digitalWrite(dataPin, HIGH); digitalWrite(clockPin, HIGH); digitalWrite(dataPin, LOW); digitalWrite(clockPin, LOW); digitalWrite(clockPin, HIGH); digitalWrite(dataPin, HIGH); digitalWrite(clockPin, LOW); // shift out the command (the 3 MSB are address and must be 000, the last 5 bits are the command) shiftOut(dataPin, clockPin, MSBFIRST, command); // verify we get the right ACK digitalWrite(clockPin, HIGH); pinMode(dataPin, INPUT); if (digitalRead(dataPin)) Serial.println("ACK error 0"); digitalWrite(clockPin, LOW); if (!digitalRead(dataPin)) Serial.println("ACK error 1"); } void SHT_waitForResult(int dataPin){ // wait for the SHTx answer pinMode(dataPin, INPUT); int ack; //acknowledgement //need to wait up to 2 seconds for the value for (int i = 0; i < 1000; ++i){ delay(2); ack = digitalRead(dataPin); if (ack == LOW) break; } if (ack == HIGH) Serial.println("ACK error 2"); } int SHT_getData(int dataPin, int clockPin){ // get data from the SHTx sensor // get the MSB (most significant bits) pinMode(dataPin, INPUT); pinMode(clockPin, OUTPUT); byte MSB = shiftIn(dataPin, clockPin, MSBFIRST); // send the required ACK pinMode(dataPin, OUTPUT); digitalWrite(dataPin, HIGH); digitalWrite(dataPin, LOW); digitalWrite(clockPin, HIGH); digitalWrite(clockPin, LOW); // get the LSB (less significant bits) pinMode(dataPin, INPUT); byte LSB = shiftIn(dataPin, clockPin, MSBFIRST); return ((MSB << 8) | LSB); //combine bits } void SHT_skipCrc(int dataPin, int clockPin){ // skip CRC data from the SHTx sensor pinMode(dataPin, OUTPUT); pinMode(clockPin, OUTPUT); digitalWrite(dataPin, HIGH); digitalWrite(clockPin, HIGH); digitalWrite(clockPin, LOW); } Tweet No Comments The Big Easy Stepper Motor Driver + Arduino Monday, November 26 th , 2012 [[Step Motor|Stepper]] (or step) motors are really cool. They are perfect for automation or any time you need a motor to turn to a specific point, at a specific speed, in a specific direction. And, unlike typical motors, steppers are able to do all of this, and hold their position when they are not moving – The trade off is that they cant move as fast, and you have to power them at full power all the time, but you get total control in return. Steppers have a minimum amount they can move known as a step. You can feel these steps if you slowly turn your stepper by hand. The most common steppers have 200 steps per revolution, so all movement is in 1.8º increments (360º / 200). ...