Materials

Tools

  • Soldering iron, solder, solder wick (or a solder sucker)
  • Angled wire cutters
  • Needle nosed pliers
  • Wire strippers
  • Computer with Arduino IDE and Teensyduino installed

Instructions

Part 1: Set up the Alcohol Sensor

  1. The alcohol sensor has two sets of three pins - solder one set together with a bit of wire - this is now the positive side of the sensor.
  2. Solder a red wire to the positive side.
  3. Look at the pins with the positive side to your right, solder the 10k resistor between the two lower left pins.
  4. The middle left pin is now ground and the upper left pin is the signal pin.
  5. Solder a brown wire to the ground pin and a blue wire to the signal pin.
  6. Before use, the alcohol sensor needs to be burned in for 24 hours. Solder the sensor’s ground and positive leads to the GND and VCC pins on the Teensy, and plug the Teensy into a powered USB hub or phone charger for 24 hours.

Part 2: Wire the Circuit Together

  1. Solder the Alcohol sensor’s signal line into pin 22 of the Teensy (or any analog input pin if you’re using a different microcontroller)
  2. Solder the buzzer’s black wire to the Teensy’s GND pin
  3. Solder the buzzer’s red wire to pin 10 on the Teensy
    • Any other digital output pin except for TX should work if you’re using a different microcontroller
  4. Break off two male header pins and solder a pair of wires to them.
  5. Solder the black wire to the Teensy’s GND pin
  6. Solder the white wire to the Teensy’s VCC pin
  7. Now you can plug the LiPo battery into the Teensy to provide it with power - just make sure you plug it in black to black.
    • Note don’t ever have both the battery and the computer plugged into the Teensy at the same time - bad things could happen.
  8. Download the Arduino code from the Simple Switch Labs’ Git repository and open it with the Arduino IDE and load it onto the Teensy.
  9. Test your circuit by wafting some alcohol near the alcohol circuit - the buzzer should start and stop pretty quickly when you bring alcohol near and remove it again, but it won’t be perfect.

Part 3: The Horn

  1. Gently remove the plastic nozzle from the party horn then use your needle nosed pliers to remove the thin plastic reed from inside the horn.  If you blow through the nozzle, it should no longer make any noise.
  2. Flatten the horn so it’s no longer perfectly round, you want it to be a bit oval - this will allow air to pass the alcohol sensor when someone tries to blow in it.
  3. Replace the nozzle onto the horn.
  4. Gently start inserting the circuit into the horn, sensor first, a little bit of Blu-Tac is helpful for keeping things stuck where they should be
    • Note use some Blu-Tac to help ensure there is plenty of room for air to bypass the sensor - you don’t want to seal up the horn
  5. Plug the battery in and give your horn a test.

How it works:

Not via any kind of blood alcohol measurement.

Because the alcohol sensor isn’t the most accurate sensor in the world, all the code really does is look for the presence of alcohol - if it sees a nice spike, it sounds the alarm.  So you can just swish something in your mouth and it will still work. You can always modify the code so the buzzer needs to see a lot more alcohol to sound the alarm.

If you’re curious or just want to experiment, you can see the data from the alcohol sensor by leaving it plugged into your computer and using the serial monitor on the Arduino IDE (it sends at 9600 bps).



Created at Havas Chi by Tyler DeAngelo & Sacha De'Angeli. Fabricated at Simple Switch Labs