Introduction: Air Quality Balloons

Picture of Air Quality Balloons

This Instructable will show you how to make giant, super cool, glowing balloons that react to surrounding air quality. Inside each balloon is a tri-colored LED. This LED reacts to data from an air quality sensor, turning green, yellow or red based on low, average, and high values.

Even without any fancy circuitry, these look pretty awesome at night. The project could be improved by adding a transistor to make the balloon illumination brighter, and by more carefully calibrating the air quality sensors to temperature and humidity.

This is a project by Stacey Kuznetsov, Jian CheungGeorge Davis and Eric Paulos at Carnegie Mellon University. Photos were taken by Chloe Fan and Iris Howley.

Please feel free to contact Stacey Kuznetsov ( if you have any comments or questions.

Step 1: Gather Materials

Picture of Gather Materials

Here are the materials you'll need to make a single balloon:
- Air Quality Sensor from Figaro (I recommend the VOC or the diesel/exhaust sensor, $10/$20 each)
-PICAXE micro-controller - 8 pin ($2.95)
- DIP-socket for the PIC ($1.50)
-Rechargeable lipo battery ($8.95)
-Tri-colored LED ($7.95)
-Either a 10Kohm resistor for sensing VOC or exhaust, or a 100Kohm resistor for sensing diesel
- Weather Balloon ($3.95)
- Access to Helium (you can probably go to a party store, or rent a tank from a welding supply shop)
- rubber band or string to tie the balloon once inflated
- (optional) connector for battery

You will also need to use
- Picaxe starter kit and cable, or some other way to program the pic
- wire
- solder/soldering iron
- electric tape
- head shrink /head gun
- pliers/wire strippers
- power-supply or some power sources around 5V to preheat the sensor

Step 2: Preheat Sensors

Picture of Preheat Sensors

Data sheet for both sensors suggests 48 hours of preheat to make the elements most stable. I've run them for about 24 hours and it seemed to work fine.

All you have to do is hook up the Power and Ground on the sensor to a power supply (at  4.5Volts) or battery (3.7-4.5 volts should work). If using a power supply, make sure it's not current- limited because multiple sensors will draw a lot of current.

You can do this on a breadboard or using alligator clips and leave it on over night.

Step 3: Program the PICAXE

Picture of Program the PICAXE

First, you need to install the PICAXE IDE and drivers for your computer from

Second you have to assemble your PICAXE programming board or whatever you choose to use to program the pic. Refer to for details on starting out with the PIC.

The code is very simple. It samples the sensor output, and if it's below, within or above certain thresholds, it turns the LED green, yellow or red. Each sensor might have slightly different thresholds. Here are the values I used, based on collecting data around my city:

'w5 = 270 'DIESEL GREEN'
'w6 = 295 'DIESEL RED'

'w5 = 448 'VOC GREEN'
'w6 = 470 'VOC RED'

w5 = 360 'EXHAUST GREEN'
w6 = 380 'EXHAUST RED'

goto runsensor

readadc10 4, w3 'SENSOR VALUE'
if w3 < w5 then 'GREEN'
high 1
low 2

if w3 >= w5 and w3 < w6 then 'YELLOW'
high 1
high 2

if w3 >= w6 then 'RED'
low 1
high 2
pause 500
goto runsensor

An easy way to guess what the green, yellow and red values might be after you already wired up the circuit is by using a voltmeter. You can see what voltage the sensor is giving off at different locations and translate that into analog values:

1023 * sensor voltage / your battery voltage

Step 4: Solder the Circuit (VOC Sensor)

Picture of Solder the Circuit (VOC Sensor)

This is the trickiest part of the project. All connections must be very solid or they will fracture from the movements of the balloon. I recommend lot's of heat shrink or electric tape around each joint.

Solder the pic socket (not the pic itself to allow easier programming). Leave about 6 inch wires between the LED and the picaxe. Solder the picaxe, sensor and battery close together.

Sensor Pins
1 - ground (this could be the battery ground or the picaxe ground)
2 - picaxe pin 4, with a 10K resistor across ground
3 & 4 - VCC (this could be the picaxe VCC or the battery VCC)

LED Pins
Green - picaxe 1
Red - picaxe 2

Step 5: Solder the Circuit (diesel or Exhaust Sensor)

Picture of Solder the Circuit (diesel or Exhaust Sensor)

This is the trickiest part of the project. All connections must be very solid or they will fracture from the movements of the balloon. I recommend lot's of heat shrink or electric tape around each joint.

Solder the pic socket (not the pic itself to allow easier programming). Leave about 6 inch wires between the LED and the picaxe. Solder the picaxe, sensor and battery close together.

Sensor Pins
1 - picaxe pin 4 with a 100Kohm resistor across ground (for diesel)
3 - picaxe pin 4 with a 10Kohm resistor across ground (for exhaust)
4 - ground (this could be the battery ground or the picaxe ground)
3 - VCC (this could be the picaxe VCC or the battery VCC)

LED Pins
Green - picaxe 1
Red - picaxe 2

Step 6: Lot's of Tape

Picture of Lot's of Tape

Put electric tape all around the sensor and piaxe, without blocking the sensor element from getting air. Tape is a DIY container for this circuit (this way you don't need any other enclosure).
Put some tape around the LED too- it could get too hot or too sharp and make the balloon pop.

Step 7: Insert Into Balloon

Picture of Insert Into Balloon

Insert the LED into the balloon, but keep the picaxe, sensor, and batter outside.

Most likely, your sensor will float at this point and the LED will turn red no matter what threshholds you set in step 1. Give it some time, it'll settle back to normal in 20? minutes.

Step 8: Inflate the Balloon!!

Picture of Inflate the Balloon!!

This step is awesome. You can now inflate the balloon! We used rubber bands to tie them off since tying the actual balloon might break the already-fragile wiring. If you're planning to set up a balloon installation, I recommend inflating the balloons on-site. They will not fit into a car :)

Step 9: Write Sensor Name on Balloon

Picture of Write Sensor Name on Balloon

Write the name of the sensors on your balloon in thick marker. 

Step 10: Go Out and Show Off!!

Picture of Go Out and Show Off!!

You can walk around with your balloon(s) or leave them in some place. Make a video and take some pictures!


Jonathanrjpereira (author)2015-12-11

Cool Instructable

Dean Wilson (author)2014-05-08

Love this :-) Did you consider using an atmega8 (or 168) chip in place of Picaxe?

john34howard (author)2014-03-07

I think it would be a lot of fun to put these types of balloons around my city. I wonder what the readings would be on those balloons. The nice thing is these balloons are very expensive either.

sunpialia (author)2013-05-12

you can find more LED lights at

SupNY (author)2011-10-17

Really intelligent piece of writing buddy, keep it up and I will keep tweeting your blog posts for you so you can get the readers you deserve! horny goat weedicariin

Exiumind (author)2011-10-14

how do i program using the flow chart?

lalubu6 (author)2011-09-18

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robert.d (author)2011-06-10

checkout led strip lights at hero led store and custom color changing balls, attractive and amazing.

alex10101010 (author)2011-03-21

Helium is spelled Helium, look in step 1 picture 4 at the helium tank. Sorry if this is a repeat.

DIY-Guy (author)2010-08-06

Very pretty.

[Humor alert, impending humor alert!]
Can we scale them down to party size and include the flatulence detector please? Instead of changing the channel on the TV in a mysterious way (as another instructable attempts to do), putting one of these at each seat during a party could identify the guilty... party poopers so to speak.

Begin Brainstorm:
But seriously, wouldn't these make wonderful garden sensor displays which could be clearly seen from inside a building on a cold winter night? I can just see it now, "The roses are turning blue dear, it looks like frost tonight. Better cover them with burlap before they freeze."

Or, it's time to clean out the chicken coop again, methane levels are getting too high.

Or, "Wow! Look how much oxygen our spider plants are contributing to the indoor air quality of our apartment!"

Or, "There's a pocket of pollution hanging over our yard. Kids, I'm sorry but you will have to stay indoors behind the air filters this afternoon."

Or, "Smog levels are at dangerous levels for heart patients today, stay out of the garden."

Any takers on these variations? :)

Nicholin (author)DIY-Guy2010-12-30


and love the garden idea.

alltootechnical (author)2010-10-30

What's VOC?

Volatile Organic Compounds is probably what this is referring to.

solesan7 (author)2010-09-13

That's a great idea, we are going to try it. Do you have any spare parts you would like to sell us (to be ecological??) Thanks!!

mcleanc (author)2010-08-22

This is a cool project. The hackerspace I'm affiliated with is thinking about using this one for one of our project nights. We can't figure out where to buy the sensors. Does anybody have any thoughts?

Algag (author)2010-08-12

can i ask where you can get weather ballons?

Algag (author)staceyk2010-08-15

thx a bunches

Algag (author)Algag2010-08-12

if anything is double posted or posted weired srry something is freaking out right now (the weather balloon question was posted before the LED question yet i replied to it)

ewilhelm (author)2010-08-03

This is an excellent Instructable! When you were selecting sensors, did you notice particulate sensors? I'm curious if the gas products of diesel combustion remain co-located with the particulates, and if the presence the gas products would be a good indication that particulates are also present.

staceyk (author)ewilhelm2010-08-03

Yes, actually, we almost included a dust sensor from Sharp (the only one I could find in this price range) Ultimately, we did not use it because it's a bit tricker to solder and it requires a very precisely-timed output pulse on its IR LED. I think we would've needed a chip with more pins for that. Diesel gas is very fine particulate matter, but the Figaro diesel sensor we used reacts to NOx- which they claim is a large component of diesel combustion... I really do wish there was a better low-cost PM sensor out there

jtpoutdoor (author)staceyk2010-08-05

what about a sensor from a smoke alarm- would that be usable?

expldoymatt (author)jtpoutdoor2010-08-06

You want to be carefull pulling apart smoke alarms unless you've had experience with radioactive materials. Most modern models are okay but older alarms contain americium. If you rupture the casing and ingest or inhale any of it you could be in trouble. Not the kind of thing to tell people to do on an instructable.

jtpoutdoor (author)expldoymatt2010-08-06

fair enough, it was just an idea, I've never pulled one apart amd I forgot some of them are radioactive- defoinately not something I would have said if I had remembered!

ildefonso (author)jtpoutdoor2010-08-09

Radioactive? wow, to think these things are installed on schools (I mean, older models, I'm sure that most schools around here hasn't changed these for at least 15 years or more). One more reason to get a Geiger-Müller tube :) .

expldoymatt (author)ildefonso2010-08-15

First of all they use alpha emitters, so no radiation is getting past the plastic housing. I'd bet good money that you'd have trouble detecting the radiation from the ground, even with high tech equipment. Secondly, it's not really enough to worry about unless you eat it or get it on you (and subsequently swallow it). This is almost impossible as long as you leave smoke alarms in their plastic housing. Thus older smoke alarms are no more dangerous than the batteries that would have powered them when they came out.

ildefonso (author)expldoymatt2010-08-15

Hi! Thanks for the answer, I imagined that the radiation levels should be really low, but I wasn't sure. Nah...... you don't know the kids around here :-S, I'm not worried about radiation coming out of the smoke alarm, I'm worried about the students doing vandal acts on these, I mean, in the past they had already broke lights, stolen some wires (phone, mainly), destroyed windows, destroyed the basketball backboard (broke it)..... I'm talking about the students in the school, not outside people, so, they could, at some point, try to just test their new baseball bat with the fire alarms (that would not surprise me).... and the Geiger-Müller was a joke, I would like to have one, just need a really good excuse to get it. Thanks!

mlmccauley (author)2010-08-12

I'd REALLY like to build this project, but I can't find a source for the sensors. Where can you buy them?

Algag (author)2010-08-12

can i also ask if one LED really lights up that entire balloon

solarblade90 (author)2010-08-04

Hey guys, why not check out my inscrutable. If your a complete beginner in electronics, than it's definitely the one for you.

gray.t (author)solarblade902010-08-10

I hope that was on purpose. I got a good chuckle out of it anyhow. :)

inscrutable: Impossible to understand or interpret

buteomont (author)2010-08-04

Massively cool idea. But remember the debacle with the LED signs in Boston a while back? (It has LEDs! It has batteries! Call the bomb squad!) I'd think twice before sticking these out in public places, especially in nervous cities like Boston!

staceyk (author)buteomont2010-08-04

Yea good point- although balloons are pretty playful... I guess we never tried leaving the installation un-attended so I can't say if someone would freak out call the police.

ildefonso (author)staceyk2010-08-09

I think that, if I program a color-changing pattern on these, tie a couple of these together, and let them go: UFO alert! really, I think that maybe I could even get some pictures of that coming out on the news :D , or at least, some youtube video.

gormly (author)buteomont2010-08-05

"Nervous cities", ok, suppose you are a cop and you come across a blinky thing stuck on a bridge, it looks harmless so you just reach up and ... Right. No, that's not what you do, (and not what you'd do) you'd call the squad house and they call the bomb squad because you just don't know... It's easy in hindsight to call someone "nervous" and ridicule them, but it's a lot better than being cavalier about it and being DEAD and risking other lives. It's so easy to be brave on the Internet (in hindsight).

jacobtriffo (author)gormly2010-08-05

The signs in question were not "blinky things[sic] stuck on a bridge, They were LED signs of space invaders from a popular cartoon, there was a ton of them, and they were art. The police in boston obviously overreacted to the greatest extent possible, and of course had the local government cover their tails. In all, its easy to call them nervous and to ridicule them because that is nothing but the truth. In fact, you can only expect more overreaction if you aren't critical of what they do. Drinking the koolaid like gormly only makes the problem worse. Case in point, I highly doubt you would find the same reaction today in boston if you left this project unattended, and its only because of public criticism that creative expression like this is now possible.

gormly (author)jacobtriffo2010-08-05

Oh so by "popular cartoon" you mean something an officer should have recognized right?

Because they spend all their off time watching toons and posting on the net? Get real. They were BLINKING things stuck on the bridge. In one case, out of reach.

The only issue was the MEDIA, not the police. If the media hadn't reacted the way it did, no one would have heard about it and it would have been a non issue. " I highly doubt you would find the same reaction today in boston if you left this project " I agree as they are ballons and ballons can't realy hold any explosive material outside the obvious...helium.

Go ahead and stick some led signs on another bridge somewhere and see if it doesn't get a similar reaction.
I wonder who called the media to report the whole situation eh? Yea, the "artists" most likely.

The truth is that the US WAS struck by terrorism in the past and prudence takes precedence in these situations.  No one was hurt by the police action, so I would rather my police department overreact than under, and again there was absolutley NO harm from their reaction except for people like you who made fun of them in hindsight.

Yea, closing a bridge for a LED sign was an overreaction, big deal, I am glad they did that than ignored it.

Asking you seriously without all the BS, if you drove a route over a bridge every day and one day you saw a LED thingy that didn't look like a cartoon you watch every afternoon, out of reach in a odd spot would your first reaction be "aww, how cute"?

Who's drinking the koolaid again?

Vermin (author)gormly2010-08-05

Helium is not explosive. It's about as inert as a gas can get. An easy mistake to make (confusing it with hydrogen) but your general lack of understanding of other issues is about as appalling as the rights US citizens have had legislated away in the knee jerk follow up to 9/11.

ildefonso (author)2010-08-08

Hi! First, thanks for sharing this great project, I find it really fun and interesting. I just have one comment: You should mention the need for a LiPo batteries charger (yes, I know, the link you have for the battery mention it, but I believe you should mention it here too). Sincerely, Ildefonso.

pixiecrossing (author)2010-08-05

Wow...I can't understand any of this. :-(

"An easy way to guess what the green, yellow and red values might be after you already wired up the circuit is by using a voltmeter. You can see what voltage the sensor is giving off at different locations and translate that into analog values:" Yeah that's a bit rough on my brain too.

yardleydobon (author)2010-08-07

"Insert the LED into the balloon...Most likely, your sensor will float at this point..."

That tripped me up for a second. Both balloons and pins can float. Perhaps it's better to say your sensor's output will float electrically.

salmansheikh (author)2010-08-06

Where do you buy the sensors? Straight from figarose?

piper1234 (author)2010-08-06

in this times if you go by the street making 'beep beep' with some lights in your hat someone will call the police cause you might be a walking bomb... (have you seen 24?) where's the line between caution and paranoid? ...beep...beep...

dragolad (author)2010-08-06

An excellent idea, this concept could be outfitted with different sensors, for example a Geiger-Muller tube, to be released into a potentially radioactive area, a floating Geiger counter if you will.

ubiquitoussmokey (author)2010-08-05

buteomont: 1.31.07... may we never forget the Mooninites: Ignignokt and Err, and what they have done for this country!

M.C. Langer (author)2010-08-03


pleabargain (author)2010-08-03

Very clever! Kudos! San Francisco, yes?

staceyk (author)pleabargain2010-08-03

thanks, not SF- I wish

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