Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Seat belt as a kill switch: need suggestions

  1. Jun 29, 2015 #1
    So I'm planning on making the seat belt to work as a kill switch for an automobile using a Reed switch and a magnet. But I'm confused as to whether I should buy or make one. If I should buy it where should I go? Please give me your suggestions as I have to find the most efficient way and I have very little time. Thank you.
     
  2. jcsd
  3. Jun 29, 2015 #2
    Most newer cars already have seatbelt sensors built in. Could you hijack that signal??
    My car even goes so far to have a weight sensor in the passenger seat to suppress the alarm when no one is sitting in it.

    However from a safety standpoint a kill switch such of this might end up being more dangerous. What happens if the sensor fails when you're driving down the highway? Or if you've been out camping in the middle of nowhere and the sensor fails?
     
  4. Jun 29, 2015 #3
    Actually this vehicle is for a competition and it won't be hitting the road much other than the few days in which the competition will take place.
     
  5. Jun 29, 2015 #4

    phinds

    User Avatar
    Gold Member
    2016 Award

    So you're saying you don't care if it's really dangerous during those few days?
     
  6. Jun 29, 2015 #5

    donpacino

    User Avatar
    Gold Member

    no, he is saying the solution doesn't need to work for 30000 hours before failure, just a few.
     
  7. Jun 29, 2015 #6

    donpacino

    User Avatar
    Gold Member

    you might be better off buying the sensor. I'm sure they have commercially available parts. go to sites like digikey or mouser
     
  8. Jun 29, 2015 #7

    phinds

    User Avatar
    Gold Member
    2016 Award

    Sure, and I agree it's almost sure to be safe but "almost sure" isn't all that great when your life could be on the line.
     
  9. Jun 29, 2015 #8
    Actually there is no threat to life,its an electric motor driven vehicle that would barely cross 25kmph
     
  10. Jun 29, 2015 #9

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    That proposed modification could be contravening your contractual agreement with your insurers. You would be advised to ask them or you could find you were not covered, if you were to have an accident and the assessor were to poke around. In the case of this particular vehicle, I would think he may be very interested in any mods you had done.
     
    Last edited: Jun 29, 2015
  11. Jun 29, 2015 #10

    donpacino

    User Avatar
    Gold Member

    there is a large difference between a design that will olny last a few days, and a design that is 'almost sure.'
     
  12. Jun 29, 2015 #11

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    If I were going to use a parachute just once - tomorrow - I would want to be pretty sure it was going to work and the 30,000 hour figure would be the one to give an indication of risk. Just as with radio nucleides, even one with a half life of 1,000,000 years could go off now. With a potentially lethal thing like a competition car, I would have a similar attitude. For a radio set or a gas cooker, I might be a bit less fussy. But this is bordering on a duty of care issue (for other competitors) and, as such, should be treated with a fair level of seriousness. You may find something in the competition rules to tell you what's acceptable or not.
    I have a worry that this is outside the remit of PF.
     
  13. Jun 29, 2015 #12

    donpacino

    User Avatar
    Gold Member


    If you were going to use a parachute 30,000 times that would be one thing, as you need to worry about the durability of the cloth, effects of repeated use on the lines. If you plan on using it once, and you KNOW it will work a few times, then that is fine and safe, because you don't need to worry about the cycling effect.

    when i said 30,000 hours i meant 30,000 hours of use, of plugging and unpluggng it. granted the number was pulled out of my butt
     
  14. Jun 29, 2015 #13

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    Even worse than failing, what if the sensor works?

    Passengers (particularly kids in the back seat) unbuckle themselves all the time. While that's worthy of a stiff reprimand, it should not be a death sentence. This kill switch is a potential death sentence. Suppose you're driving on a curvy mountain road (no guard rails) in Colorado with a thousand foot drop to one side toward that campsite in the middle of nowhere. Suppose that, just as you're about to round yet another curve, your passenger unbuckles the seat belt and the kill switch turns off the engine.

    This is a massively bad idea. What made you think this idea would help you win the competition?
     
  15. Jun 29, 2015 #14

    berkeman

    User Avatar

    Staff: Mentor

    @TheNerdyGuy -- I think you have gotten good responses in this thread, and I hope you take them to heart.

    BTW, there is a difference between a kill switch, and an interlock that doesn't let you start the vehicle if the seat belts aren't fastened for occupied seats. You might explore that option instead. Thread is closed.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Seat belt as a kill switch: need suggestions
  1. Need a book suggestion (Replies: 3)

Loading...