Hi. Sorry if something like this has been done, this is my first post here.

After some deaths from car airbags child safety devices became manditory. They are based on weight though, and not proximity. Most people killed by airbags are killed because they are right on top of it when it goes off - if they are far enough away the airbag will never even hit them; they go into it. Modern car airbags only turn on if there is more than 100lbs on the front seat. This method is problematic because sudden manuevering before an accident can lift a person off of the seat, thus deactivating the airbag right when it is most needed. Also some adults are only ~100 or so pounds yet still need an airbag. So my idea is for airbags to be controlled by a proximity sensor on the dashboard. This would be extremely simple to implement, and if somebody came too close to the dashboard the airbag would not be able to go off, causing injury. However if somebody lighter than 100lbs, like a child, was sitting on the seat but at a safe distance it would still go off. The actual sensor could be ultrasonic or infrared, either way works.
-- DIYMatt, Mar 27 2009

//Most people killed by airbags are killed because they are right on top of it //
So, maybe in such cases, better to have an airbag that deploys from the headrest, a smidgin before the dashboard airbag, thereby safely sandwiching the hapless, un-belted passenger. [-]

BTW, would an ultrasonic sensor be able to react quickly enough?
-- AbsintheWithoutLeave, Mar 27 2009


hello and welcome DIYM. AWOL is probably having a bad hair day or something ...

I am however in no position to judge this idea at all - airbags scare me and I wish you hadn't reminded me that I have one.
-- po, Mar 27 2009


//AWOL is probably having a bad hair day //
Now, it's funny you should say that.
-- AbsintheWithoutLeave, Mar 27 2009


Don't put your baby any place that isn't explicitly allowed in the owners manual. Don't lie down on the wheel while driving. Always wear your seatbelt. If you pass out while driving you do so at your own peril. If you are too obese to be compatible with the safety devices in a car those devices should be disabled by the dealer and you drive at your own peril.
-- WcW, Mar 27 2009


Jeezus, why is everyone so anti this idea? What a miserable lot!

It makes perfect sense to me, if it's true that proximity to the airbag is the main risk factor. In response to AWOL's question about response times for an ultrasonic sensor, it's not relevant. The sensor would monitor the position of the occupant continually, and would de-activate the airbag if they were too close; it doesn't have to do anything at the time of impact, and it wouldn't really matter if its response time were measured in seconds.

Welcome, DIYM.
-- MaxwellBuchanan, Mar 27 2009


Hello, nice to meet you.
It sounds OK to me. Simplicity and robustness are key. I think a series of sensors would have the advantage of being unlikely to fail at the same time. I'm thinking of a grid of near-infrared LEDs which reflect off the seat. The distance can be determined by the brightness of the reflection and the cross-sectional area of the object on the front seat by the fraction of light reflected back at greater intensity than the reflection from the seat. Add these intensities by analogue means and use the resulting intensity to determine (hand-waving now ensues) the force of the airbag.
I would prefer a car interior filled with transparent "custard", but it would probably be quite heavy.
-- nineteenthly, Mar 28 2009


There's supposedly some kind of utility fog solution, theoretically, where motes join together on impact and make the volume in front of the occupants springy, but we can't use that here because it's effectively a nanotech solution.
-- nineteenthly, Mar 28 2009


Maybe this should be a seperate topic, but in response to 21 it seems that it would be better, instead of having an airbag that deploys with varying force, to have an airbag with a varying force limiter. Now you hit the airbag, and it will resist your force until a plug pops out and releases the air, which it releases at a set rate. What if you changed the number of plugs that opened up for the speed of the crash? So nomatter what the speed was the airbag would always provide just the right amount of force to slow you to a stop at the dashboard. Whether the occupant had a seatbelt on could also be factored in.
-- DIYMatt, Mar 29 2009



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