DIY Airbag, explosions included

AnAirbagSavedMyLife

Your car’s airbag is one of the major engineering accomplishments of the auto industry. In an accident, a whole host of processes must take place in sequence to keep your face from slamming into the steering wheel, and ¬†everything must happen in just a fraction of a second. [Steve] over at Make thought it would be a cool idea to discover what actually goes in to saving a life with an airbag and decided to build his own.

The electronics of the build consisted of an accelerometer and an Arduino. A lot of research, development, and experimentation has gone into the algorithms that trigger airbags, but [Steve] decided to keep things simple: when a sudden acceleration is detected, set off a small charge of black powder.

The airbag itself is ripstop nylon reinforced with canvas, contained in a small wooded box fitted with hinged doors. All these components are put on wheeled aluminum test rig, manned with a honeydew melon crash test dummy, and pulled into a short wall at a few miles per hour.

Despite [Steve] not putting hundreds of thousands of man hours into the development of his airbag – unlike the ones you’ll find in your steering column – his device actually worked pretty well. While not a complete success, he did manage to come up with something that both looks and acts like the familiar device that has saved countless lives.

Comments

  1. dALE says:

    Will they be selling at home kits?

  2. nelsontb says:

    why not just an analog accelerometer and an opamp?

  3. Tyler says:

    Interesting to note how many cars with airbags did not use an accelerometer.

    • Greenaum says:

      What do they use then? And in a way, isn’t a simple G-force sensor a kind of accelerometer? And if not that, then what?

      • Tech Joker says:

        I am no expert, but especially with all the side impact airbags… a lot of airbag systems use a combination of sensors that monitor impact location (side and front, mostly), speed at impact, and other factors to determine if to deploy the airbag or not (some also may be deployed at different inflation pressures and rates (multiple charges). The sensors may take the form of ‘switches’ in the bumper mount, or more recently ‘radar’ that determines locations, speeds and size of nearby objects. Many systems also utilize pressure sensors in seats to determine if the seat is occupied, If the seat isn’t occupied the airbag isn’t deployed.(Insurance mandated since airbag deployments tend to total cars by tearing up the dash, steering wheel… not to mention the airbag itself must be replaced at great expense.).

  4. sparkygsx says:

    Probably because you’d want to use more than just the amplitude to decide if the airbag should be triggered. For example, you could use an algorithm to measure the long-term noise level to prevent triggering when the sensor is faulty, you could use the information from multiple sensors, and you could use information about the shape of the signal to determine if it’s really a crash or measurement error.

    Obviously, both false positives and false negatives are very dangerous, making a seemingly simple system very difficult.

    What surprised me in the video was the statement “how hard to trigger the airbags”. I’d expect the triggering to be purely digital. Do these systems somehow alter the speed of deployment based on the sensor data, and if so, how does that work?

  5. 1000100 1000001 1010110 1000101 says:

    I love this mindset. Practical? Probably not. But just satisfying the curiosity of how things work, and figuring out how to do it, and then doing it is wealth immeasurable.

  6. Mr. Torgue says:

    I have one question for you:

    EXPLOSIONS?

  7. NewCommentor1283 says:

    am i the only one that couldnt find the next button on the linked site?
    for such a complicated project involving so much learning,
    all i could see was one paragraph and a video.

  8. KillerBug says:

    Until very recently, most airbags were designed to only detonate when two sensors inside the front bumper were both activated within a few MS of eachother. Not only did this prevent airbags from going off when the car hit a hard bump while going down the road or when there was a rear impact where the bags would only make injuries worse, but it also prevented them from going off if a sensor failed and shorted out. You might wonder about frontal impacts where the front bumper does not depress on both sides…such impacts result in spins, and the airbag would do more harm than good in these cases. The accelerometers came into use with newer cars that have more than the two airbags required by law. They ensure that only the needed airbags detonate, but they only target the detonations…using them with no redundancy would result in tons of unnecessary deployments that would cause crashes and (in the case of a crash not caused by these bags) would cause them to detonate too early to do any good. Plus, any time you have an explosive charge activated by electronics pointed at your customer you want to have redundancy in case something goes wrong with one of your sensors, a wire, some RFI, etc…

  9. Dr.CoughnSpit says:

    wouldn’t it be a sudden deceleration from the crash that would trigger the airbag?

  10. Bruno says:

    Screw airbags, replace the bag with an anvil with a spike and double the charge in the steering wheel. I bet cases of reckless driving will drop dramatically, not to mention mortality rate shooting up through the roof in fender benders. Safety through fear…. ROFL. Sorry no point to my post. Other than awesome project.

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