Loading ...
Sorry, an error occurred while loading the content.

Re: [beam] Age and sigh of relief

Expand Messages
  • Sathe Dilip
    This should help: http://repairfaq.ece.drexel.edu/REPAIR/F_safety.html Dilip
    Message 1 of 7 , Jul 1 5:47 PM
    • 0 Attachment
      This should help:

      http://repairfaq.ece.drexel.edu/REPAIR/F_safety.html

      Dilip
      ----------------------------------------------

      Ori wrote:

      >>Snipped
      >>
      >
      >When you open up a monitor, you short out all of the connectors you can with
      >a screwdriver, right? It discharges everything, if I'm not mistaken. I'd
      >definitely like to know safe proceedures about this - I'm opening up a
      >monitor tomorrow.
      >
      >>Snipped
      >>
    • Sathe Dilip
      Actually at high frequencies, skin effect takes over. The current flows through the outer shell of the body & vital organs (like heart) are not affected.
      Message 2 of 7 , Jul 1 6:08 PM
      • 0 Attachment
        Actually at high frequencies, skin effect takes over. The current flows
        through the outer shell of the body & vital organs (like heart) are not
        affected. Irrespective of what current was switched on & off, the
        actual current flowing through the body depends on the voltage applied
        and the effective resistance offered by the body. If the points of
        contact offer say a few kilo ohms (not unusual for dry skin) the current
        flowing will be a of the order of tens of mA.

        Above is the cold analysis. I am not trying to play down the danger or
        the pain that Richard had to go through. HP used to have an
        article/application note on electrical safety in hospitals. They had
        explained whole scenarios where an apparent unrelated activity (such as
        a janitor plugging a vacuum cleaner in a nearby socket) could kill a
        patient wired for cardiac catheters. The amount of current that sends a
        heart into fibrillation (when directly flowing through the heart -
        actual current flowing through the whole body could be much higher) is
        as low as 20 microAmps. That note categorized the levels of electrical
        shock with the amount of current flowing through the body. Most
        dangerous range is something like 18 to 300 mA. At higher currents (3A
        & above if your body resistance is so low), it is in a way safe because
        it causes local burns and punctures only.

        Dilip
        -------------------------------------

        Ori wrote:

        >>Got 295 Volts DC at 45 Amps switched on and off at 20 KHz from a servo
        >>amplifier at work once!
        >>
        >
        >Ouch! You're obviously alive to tell the tale, though - what happened, both
        >terminals came to one finger or something? Couldn't have gone through your
        >entire body.
        >
        >i got
        >
        >>zapped by a Computer monitor's flyback (underside of the board, but the
        >>big cable, thank God). I got a cracked picture tube (powered up)
        >>discharged through me once. That actualy bugged me the least of all!
        >>
        >
        >When you open up a monitor, you short out all of the connectors you can with
        >a screwdriver, right? It discharges everything, if I'm not mistaken. I'd
        >definitely like to know safe proceedures about this - I'm opening up a
        >monitor tomorrow.
        >
        >>At work, I've gotten tot he point where if I touch the 208 volt line, I
        >>don't notice it sometimes...
        >>
        >
        >I've got shocked from the wall so many times, I rarely notice. I was working
        >on an open digital clock while it was plugged in - I needed it to be plugged
        >in so that I could find out what was wrong, and I wasn't touching the corner
        >of the board, where the transformer was. After I found the problem, I picked
        >up the board, and I touched the soldering joints where the wire comes in
        >from the wall. It was only two fingers, and I didn't notice for a few
        >seconds - but because my fingers were twitching at a good 60 hz, I realized
        >what was going on :)
        >
        >Ori
        >
        >
        >To unsubscribe from this group, send an email to:
        >beam-unsubscribe@egroups.com
        >
        >
        >
        >Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
        >
        >
      • Robert Morris
        I m 28, been on the beam list a few years now, back when it was hosted at SGI. Haven t had the time to build much in the way of robots, but I occasionally get
        Message 3 of 7 , Jul 1 6:13 PM
        • 0 Attachment
          I'm 28, been on the beam list a few years now, back when it was hosted
          at SGI. Haven't had the time to build much in the way of robots, but I
          occasionally get some ideas and play around with them on the
          breadboard.

          As far as my horror story, I got shocked adjusting the spark gap of a
          Tesla coil back in ninth grade. My fingers were just a little too close to
          the metal part of the pliers I was using. The voltage at the spark gap
          was about 600 Volts AC at ? Amps. Knocked both me and the chair
          I was sitting in back a ways. Mouth tasted like I had been chewing
          pennies for quite a while too.

          Robert


          At 06:00 PM 7/1/2002 -0500, you wrote:
          >Got 295 Volts DC at 45 Amps switched on and off at 20 KHz from a servo
          >amplifier at work once! That burns!!! I had a burn mark from the
          >terminal block's underside matching each stator phase output: øR, øS,
          >and øT! Stung for a couple weeks!
          >
          >I'm weird though, I take the shocks. The funny thing is I finished what
          >I was doing to the amp after about a 10 second "recovery of my senses".
          >Then I went and dealt with the injury. I did the same thing when i got
          >zapped by a Computer monitor's flyback (underside of the board, but the
          >big cable, thank God). I got a cracked picture tube (powered up)
          >discharged through me once. That actualy bugged me the least of all!
          >
          >At work, I've gotten tot he point where if I touch the 208 volt line, I
          >don't notice it sometimes... Must be lower current, but it does drive
          >those servo amplifiers at 45 amps 295 volts DC.
          >
          >That 220 AC had to have hurt just as much, if not more!!! There's a LOT
          >of Amps behind that!!! Geez!
          >
          >I think the moral of the story is I'm insane and get shocked too often.
          >
          >Richard Piotter
          >
          >
          >fz1450 wrote:
          > > thought for a while i might be the oldest around here, i'm 52,
          > > thanx wilf ;-)) (dutch roots???)
          > > i'm into beam since last, let's say november or so ...
          > > i have also been playing around with electronics since
          > > i was young. Never got burnt to much, although i once , must been 14
          > > or 15, grabbed a wire with 220V on it, i was so 'shocked' that i'm
          > > still paranoia about it, frans
          > >
          > >
          > >
          > >
          > > To unsubscribe from this group, send an email to:
          > > beam-unsubscribe@egroups.com
          > >
          > >
          > >
          > > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
          > >
          > >
          > >
          >
          >
          >--
          >
          >
          >Richard Piotter The Richfiles Robotics & TI web page
          >richfiles@... http://richfiles.calc.org
          >
          >
          >To unsubscribe from this group, send an email to:
          >beam-unsubscribe@egroups.com
          >
          >
          >
          >Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
        • Richard Piotter
          Exactly! All the stuff like that were skin burns. Some white powder residue sometimes. Painful, but tolerable. As always use one hand only, and if you re
          Message 4 of 7 , Jul 2 10:24 PM
          • 0 Attachment
            Exactly! All the stuff like that were skin burns. Some white powder
            residue sometimes. Painful, but tolerable. As always use one hand only,
            and if you're grounded, use the grounded hand to work. don't want
            current to go to ground to your other hand from the one you're worknig with.

            I had a foot ground at the time, and the zap mainly I think went from
            phase to phase, but I could feel my entire side from arm to foot tighten
            and get all warmish. I'm sure that was real healthy!

            The flyback was underside, two high frequency, high voltage pins accross
            two fingers. Left a pair of mounds with white powder inside at the two
            contact points. That was the closest I ever came to going unnaturaly
            unconcious, but I never got passed everything getting all grey hazy.
            That one ws from a live image adjustment, and my habit of moving the
            monitor. It has a pair of ridges that I always used like handles, but
            with the case gone, it was right under the flyback.

            I forget the pain easy... It's the smell!

            Always be safe and not imitate me! Seriously. I do be careful, but
            everyone has that potential for mistakes. I just make many of them.

            Richard Piotter


            Sathe Dilip wrote:
            > Actually at high frequencies, skin effect takes over. The current flows
            > through the outer shell of the body & vital organs (like heart) are not
            > affected. Irrespective of what current was switched on & off, the
            > actual current flowing through the body depends on the voltage applied
            > and the effective resistance offered by the body. If the points of
            > contact offer say a few kilo ohms (not unusual for dry skin) the current
            > flowing will be a of the order of tens of mA.
            >
            > Above is the cold analysis. I am not trying to play down the danger or
            > the pain that Richard had to go through. HP used to have an
            > article/application note on electrical safety in hospitals. They had
            > explained whole scenarios where an apparent unrelated activity (such as
            > a janitor plugging a vacuum cleaner in a nearby socket) could kill a
            > patient wired for cardiac catheters. The amount of current that sends a
            > heart into fibrillation (when directly flowing through the heart -
            > actual current flowing through the whole body could be much higher) is
            > as low as 20 microAmps. That note categorized the levels of electrical
            > shock with the amount of current flowing through the body. Most
            > dangerous range is something like 18 to 300 mA. At higher currents (3A
            > & above if your body resistance is so low), it is in a way safe because
            > it causes local burns and punctures only.
            >
            > Dilip
            > -------------------------------------
            >
            > Ori wrote:
            >
            >
            >>>Got 295 Volts DC at 45 Amps switched on and off at 20 KHz from a servo
            >>>amplifier at work once!
            >>>
            >>
            >>Ouch! You're obviously alive to tell the tale, though - what happened, both
            >>terminals came to one finger or something? Couldn't have gone through your
            >>entire body.
            >>
            >>i got
            >>
            >>
            >>>zapped by a Computer monitor's flyback (underside of the board, but the
            >>>big cable, thank God). I got a cracked picture tube (powered up)
            >>>discharged through me once. That actualy bugged me the least of all!
            >>>
            >>
            >>When you open up a monitor, you short out all of the connectors you can with
            >>a screwdriver, right? It discharges everything, if I'm not mistaken. I'd
            >>definitely like to know safe proceedures about this - I'm opening up a
            >>monitor tomorrow.
            >>
            >>
            >>>At work, I've gotten tot he point where if I touch the 208 volt line, I
            >>>don't notice it sometimes...
            >>>
            >>
            >>I've got shocked from the wall so many times, I rarely notice. I was working
            >>on an open digital clock while it was plugged in - I needed it to be plugged
            >>in so that I could find out what was wrong, and I wasn't touching the corner
            >>of the board, where the transformer was. After I found the problem, I picked
            >>up the board, and I touched the soldering joints where the wire comes in
            >
            >>from the wall. It was only two fingers, and I didn't notice for a few
            >
            >>seconds - but because my fingers were twitching at a good 60 hz, I realized
            >>what was going on :)
            >>
            >>Ori
            >>
            >>
            >>To unsubscribe from this group, send an email to:
            >>beam-unsubscribe@egroups.com
            >>
            >>
            >>
            >>Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
            >>
            >>
            >
            >
            >
            >
            > To unsubscribe from this group, send an email to:
            > beam-unsubscribe@egroups.com
            >
            >
            >
            > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
            >
            >
            >


            --


            Richard Piotter The Richfiles Robotics & TI web page
            richfiles@... http://richfiles.calc.org
          Your message has been successfully submitted and would be delivered to recipients shortly.