Picture of Gas Cap
Since you've gotten into electronics, haven't you wondered if there is a fart sensor out there?  I sure did.  I discovered that if you use a methane sensor, especially the MQ-4, even at very low concentrations, it reads farts.  What if you combined that into a hat with an LED Bar Graph and a XBee?  Exactly.  The Gas Cap was made with that in mind.  For around $100, you can build your own Gas Cap, a human gas-operated LED Bar Graph on a hat.  So, you fart into the methane sensor, wirelessly transmit that data to the hat, and watch the LEDs light up so that your friends can see how horrible it was.

Feel free to leave any questions or comments.

Step 1: Parts

Picture of Parts
You will need to purchase the following from Sparkfun:

Relevant Parts:

Methane CNG Sensor  $5
330 Ohm Resistor  $0.25 (2)
XBee Series 2 - Wire Antenna  $26 (2)
Lilypad Arduino 328 Main Board  $22
Lilypad XBee  $15
Lilypad LED PCB Set  $5
Lilypad Simple Power  $5
FTDI Basic  3.3V (for programming the Lilypad) $15
110mAh LiPo  $7
850mAh LiPo  $9
XBee Explorer  $25
XBee Breakout Board  $3
XBee Headers for Breakout Board  $1 (2)
JST 2-pin Through-Hole Connector  $1
SPDT Mini Power Switch  $1.50


Red LED (10)
Green LED
LiPo Charger Basic  $10
Mini-B USB Cable
A Black Soft Cotton Hat
Altoids Smalls mint tin
Soldering Iron
Conductive Thread  $3
Long Wooden Stick or Umbrella
Hot Glue Gun
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Totally cool idea. My wife just didn't understand... I want to make one of these. It would be the perfect for someone I know. Though I am concerned with reduced lifespan of the sensor under whole milk circumstances (one does have to test it right)?

I find it so intriguing that at your age, you have been able to conceptualize so many of your ideas. Good for you, man.

I do have two questions for you. What inspired you to get into electronics and microcontrollers at your age? Second, I have a younger sister who I am trying to teach electronics fundamentals to. What has helped you learn? What methods were most effective for you?

Again, great job.
Qtechknow (author)  huck alexander3 years ago
Awesome! Thanks for the comment!

I wanted to get into electronics because I was bored with video games and TV. One day, my dad had found MAKE magazine, we bought a soldering kit, and I made more and more electronics from then on. The way I learned is I got: MAKE magazine, a small soldering kit, a soldering iron, Getting Started with Arduino (book), an Arduino, plus many other components. I made the ArduSensor Fun Pack (also one of my Instructables, for sale at my website, www.qtechknow.com) for beginners to start electronics! They are plug-in-play sensors for Arduino. I recommend that you get an ArduSensor Fun Pack for your sister to get started with electronics, plus all of the stuff mentioned above (if you don't already have it!).
zomfibame3 years ago
Mighty, mighty, mighty COOL. too funny!
ka1axy3 years ago
Not to detract from the sheer awesomeness of this design, but it did cause me to think that perhaps this reminder is overdue:

Just because it *can* be built, doesn't mean it *should* be built.

//thank you for your attention
You are just jealous of this young man's epic awesomeness. so go troll yahoo ...
I am jealous.

Also glad I don't work in a closed space with him.

Qtechknow (author)  ka1axy3 years ago
Yay! Thanks!
razamatraz3 years ago
Top notch work good sir.

A bit expensive but I imagine a wired version would be half as much (or less).

I used to work in a gas plant and the H2S detectors also work and level is more proportional to the stink since it is not the methane component that actually smells bad. It was kind of funny when someone wearing a personal H2S monitor would set it off in the lunch room.

Qtechknow (author)  razamatraz3 years ago
Thanks for the comment! Since you mentioned H2S, I think I might make an ultimate fart evaluation kit that evaluates an H2S sensor, a methane sensor, and a microphone to detect the REAL value!
Sounds like a cool idea. Combine all aspects of fart nastiness.
yoyology3 years ago
This is a device of epic awesomeness. I applaud you, sir!
Qtechknow (author)  yoyology3 years ago
Thanks for the comment! If you are going to Maker Faire this weekend, try and find the kid with the farting hat!!!
Man. I wish. It's a long way from Tulsa to SF. :-(
Stavros!19 days ago

You know, something like this to hang in the bathroom at work, or on the door to give fair warning to other people would be an interesting idea....

banker2 months ago

Hey, Everybody! Fart in my face so I can measure your fart. It's for my research.

That's just weird.
tp.pa.122 months ago

Neat idea, but I know the level of my fart by how loud my wife screams "Man That Smells" & if there is " I think I'm going to puke" well, what more is needed to be said.


jooly42 months ago

Oh my goodness! What fun for the guys in my family. I live with five of them and the other would love this. Guys really are so different than the females of the species. I had so much fun with my nutty sons, their friends, and my grandsons. Keep on being a nut young one.

MarkFisk2 months ago

Very nice. Now if you could harness the energy and save the world with a truley renewable enegry source!

cart5623 months ago

I don't need this for my friends to know how horrible my farts are....

gpay101 year ago
This idea would be great if it could sense carbon monoxide! I would buy one for my grandkids to wear to school (our schools have a lot of incidents of faulty heaters and carbon monoxide poisonings)
diy_bloke gpay104 months ago

use the MQ7 or MQ9 sensor: http://playground.arduino.cc/Main/MQGasSensors

Hey, what's up Q(uinn). :D ITS MEEEEEE! Guess.

supermitch1 year ago

Hi Qtechknow! I read about you in Popular Science and I thought "I know that kid! He's the one who made the number-one prize winner for Instructables I've wanted to make." I had looked at this project months earlier, and thought it was really cool. Finally, when we picked our annual MAP goal for school (just something you want to improve on), I picked technology. I decided I would build the Gas Cap. I just recently received most of the parts via UPS. I've been trying to get my XBee to register to the X-CTU I just downloaded, and it wouldn't find the serial USB port. I quickly learned that it was because I didn't install the FTDI drivers, so I plugged in my FTDI Basic and downloaded them from ftdichip.com. Now the USB serial port is registering, but my XBee still won't connect. Its power light is on, and I am using a Mac, so I sort of have to interpret what the Windows X-CTU tutorials mean. If you could write a few comments to help me or write a follow-up Instructable about X-CTU, that would be great!

Qtechknow (author)  supermitch1 year ago

I'm not exactly sure what is happening. Since Digi released this recently, I'd recommend using the more reliable Windows version, just to be safe. At the moment, I'm downloading the X-CTU for Mac to see what is happening. Thanks!

SGT. Desert3 years ago
you are super smart
Qtechknow (author)  SGT. Desert1 year ago
Hey Qtechknow,
I read about you in a popular science magazine. You're amazingly smart!!!!!!!!!!!!!!!!
Qtechknow (author)  whittler1231 year ago
So does the methane sensor act like a switch? It senses gas and completes the circuit?
Qtechknow (author)  Adambowker983 years ago
Not entirely; the gas sensor changes resistance instead of acting like a switch. In my code, I change the bar graph according to the resistance of the gas sensor.
So if I used a cluster of LEDs rather than a bar graph, would the LEDs get brighter as the fart got worse? And the LEDs not shine so brightly because of added resistance whenever the fart is kinda small?
Qtechknow (author)  Adambowker983 years ago
You should also try that; I don't usually do electronics without programming!
Could you make this as a pocket fart detector with just a few LEDs and no bar graph?
Qtechknow (author)  Adambowker983 years ago
You could, but that would need an entirely different format and different instructable. You could always try!
Could I wire some LEDs to a switch and then a methane sensor and then to a battery? You turn it on and the brightness of the LEDs determines the level of the fart?
Qtechknow (author)  Adambowker983 years ago
Try it!
randsroark3 years ago
Nice job!

Can you explain the AT commands for the XBee? Like, what does the ATJN 1 command do? Better yet, where do you find Digi's AT command list?
thealeks3 years ago
now i would use this to detect other peoples farts(and emit a beep or have the leds where i can see them) before my nose does, so i dont have to smell them. how many times have we been on elevators and a methane sensor at waist level could detect the fart before it reaches our nose, allowing you possibly enough time to get off at the next floor, saving you from the stench.

this instructable is brilliant!
ka1axy thealeks3 years ago
Bonus points for, well, a pointer!

...so you can indicate "who dealt it".
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