Electric shock toy safety question

Discussion in 'The Projects Forum' started by erlend, Dec 14, 2008.

  1. erlend

    Thread Starter Member

    Feb 8, 2008
    18
    0
    My cousin's husband asked me about an electric shock circuit. He
    remembers at school some kid made joke suitcase, that if picked up
    zapped the recipient.

    I know the circuit, and I strongly expect it to be the same one used
    in the practical joke pens and staplers. It just involves a DPDT
    relay, a 100uF capacitor, a small transformer and a 9v battery.

    The basic idea is that the capacitor is charged up (to 9v) triggering
    the coil which then disconnects the battery and discharges the
    capacitor through a transformer which can step the voltage up. The
    transformer has primary/secondary impedances of 1.2kOhms / 3.2Ohms
    (leading to a step-up factor of about 20).

    My question is just - how safe is this circuit? He wants to make it
    to demonstrate some electronics to his son (and I agree with him that
    there is a lot in it for a boy to learn).

    I calculated the output energy of each pulse,
    E = 0.5 * C * V^2 = 4 mJ,
    which is very low, so I told him it's fine if he's sensible, and keeps
    the output away from the face etc. I just want to check here that my
    logic is sound.

    Thanks.
     
  2. leftyretro

    Active Member

    Nov 25, 2008
    394
    2
    The problem with trying to characterize shock safety is that different subjects can react quite differently to the same voltage/current shock value. Some people might react quite violently and jump back, trip over something and split their head open, while others might just twitch a little. So electrical physics aside, because of the unpredictable response I would say that no shock toy is really safe and would be foolish to think otherwise.

    Lefty
     
  3. erlend

    Thread Starter Member

    Feb 8, 2008
    18
    0
    Then by the same argument jumping out and scaring someone would be foolish and dangerous; horror movies should carry a disclaimer "Pleae make sure you are sitting down during this production." just in case someone jumps and falls badly.

    It's really the electrical safety I'm interested in here.
     
  4. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,699
    907
    Yes, given the right conditions.

    I don't think you understand what leftyretro said. Why did you ask the question?

    John
     
  5. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Some people have dry skin and will not feel a little shock.
    Other people sweat and conduct the full shock.

    Some people are frail and will be killed by a little shock.

    Don't do it, think of something less dangerous and less stupid.
     
  6. erlend

    Thread Starter Member

    Feb 8, 2008
    18
    0
    I live in a country where electrics are heavily regulated. Even in my country I can go into a joke shop and buy electric shock pens and lighters, electric shock roulette games and quizzes... I have never yet heard of a single person who has been harmed by these in any way - it would have been all over the news if it had happened and the devices would be immediately banned.
     
  7. leftyretro

    Active Member

    Nov 25, 2008
    394
    2
    Well then it might be best for you to research your countries electrical regulations for a definition of what would comply as a "safe" shock toy, because I don't think anyone here is going to give you a specific value. You might also contact a lawyer about any possible liabilities you might incur pursuing this kind of project.

    Please don't take this personal. This forum often gets questions about designing and building shock type devices and the consensus over time seems that it is just not a good idea to help or otherwise encourage those that want to pursue this type of project.


    Good luck
     
  8. Videogamer555

    New Member

    Mar 27, 2013
    4
    0
    While I won't recommend that you SHOULD do it, I also won't tell you to NOT do it. The circuit you are recommending sounds like a safe circuit. 4mJ pulse per pulse electric shock applied to the surface of the skin isn't enough to stop a heart or even put it into fibrilation. A shock this weak would have to be applied directly to the heart (by surgically placing wires inside the body) to induce such a fatal condition in the subject.

    Don't worry. If you think someone's gonna be killed by this project you are suggesting, you are mistaken. If that's your only fear keeping you from going ahead with this project, then you should continue your project, because your fear is mistaken in this case.
     
  9. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    way to bring back the dead on your first post.. Notice the thread date.. last post in 2008.. 5 YEARS AGO. ;)
     
  10. Videogamer555

    New Member

    Mar 27, 2013
    4
    0
    I was just doing some research into these shock pens, and found this thread in google search results. I figured I'd add my 2-cents.
     
  11. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    The OP died from an accidental electric shock, and was never heard from again... ;)
     
  12. edwardholmes91

    Member

    Feb 25, 2013
    186
    19
    And why not... it seems out of all the responses yours answered the question the best. I will however refrain from expressing my opinion on this project and whether I think it's safe/should be undertaken.
     
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