Dc shock

Discussion in 'General Electronics Chat' started by MIRINGU, Aug 4, 2010.


    Thread Starter Active Member

    Mar 18, 2007
    Its said that it better to receive an Ac shock rather than Dc shock . What can u do or where to touch to get a Dc shock?
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
  3. tom66

    Senior Member

    May 9, 2009
    From what I've heard, it's much worse to get an AC shock than DC.

    I wouldn't recommend you go looking around for a high voltage DC shock. The one place you will find a dangerously high DC voltage (~350V) is inside a computer power supply, after the bridge rectifier. But this kind of shock can easily be fatal, so don't go poking around a computer supply without proper precautions!!
  4. beenthere

    Retired Moderator

    Apr 20, 2004
  5. Jaguarjoe

    Active Member

    Apr 7, 2010
    According to Thomas Edison, AC is much worse.
  6. marshallf3

    Well-Known Member

    Jul 26, 2010
    In my opinion DC hurts more, but it's been years since I've had the pleasure. Back when I was working on television sets (made good pizza money in college) I got hit but the 300V DC B+ of many an old tube set and it was often worse than getting hit by the 25 KV picture tube anode supply. There was one exception and it came on a SOny 21" CRT I was replacing. Discharged the anode, left for lunch and when I came back the cliplead I left the anode shorted with had popped off at its ground point. Not thinking I reached for it and was knocked 10' HARD into the bench behind me despite only touching it with one hand and no contact with the ground of the CRT. What some peole don't undertand is that older CRTs, much like car batteries, can build voltage back up over time due to some remaining polarization. This would have all been DC but at a potential capable of inducing a strong current - which I believe is the major determining factor as to how badly a shock "hurts" instead of the voltage potential it came from.

    DC actually hurts, AC gives a different feeling that hurts in a different way - jhard to describe.

    Now that I've got to deal with 480V 3 phase on an occasional basis I can tell you that fromobservations AC can be more dangerous. As most electricians will admit I have a tendency to tackle small repairs on live circuits, for instance changing a fluorescent ballast in a room that you'd have to kill all the lights in if you wanted to change it on dead wiring. All the plant and office lighting is 277V (one leg of 480V to neutral) and it's a simple matter of cutting the 277V supply wire first then replacing the darn thing in relative safety. You then strip the supply wire and hook it back up to the ballast. No big deal with insulated tools and those Waco Wall-nut connectors http://www.amazon.com/Wago-51038057-100PK-Yellow-Connector/dp/B000GAVAI0

    Here's the odd part I'm getting to. I've changed at least a hundred ballasts since we took possession of the building (tons were initially out) so there have been rare occasions that I've accidentally made contact with the live 277V supply leg. I'm wearing dry rubber soled shoes and on a scissor lift platform that has rubber tires yet that line will still shock the devil out of you if you so much as accidentally brush against it. Even at 60 Hz there's enough coupling from your body through the air to allow a rather awakening shock.

    Disclaimer: I certainly don't condone working on live circuits and it's against code to do so it most every situation but a few of us seasoned vets still do. This little story should remind you that you don't have to have a hard ground to get shocked, under some situations just being coupled to the air is enough.
  7. t06afre

    AAC Fanatic!

    May 11, 2009
    The maximum current that can cause the flexors of the arm to contract but that allows a person to release his hand from the current's source is termed the let-go current. This value is about 75 mA DC for a grownup. Then it comes to AC the let-go is frequency depended se figure.
    The smallest current required to prevent the release of an electrically live object occurs at a frequency of around 50 Hz. Above 10 KHz the neuro-muscular response to current decreases almost exponentially.
    IEC 60601 part 1 Medical electrical equipment-General requirements for basic safety and essential performance. Difference then it comes to AC and DC. I have included a table showing some values. Is is somewhat technical. Use Google to find out about technical terms. All AC values are in RMS, and current values are in uA
  8. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    one of the problems you'll run into is arc flash as opposed to electricution. AC, due to it's wide use, is prevelant, however, DC is a real problem in that in many cases it is not current limited.

    I once worked with an electrician that was changing the quick connector out from a 36 volt fork truck battery. He had the two cables come together in his hand. I didn't view his injuries, but there was plenty of molten metal lying around the floor.
  9. marshallf3

    Well-Known Member

    Jul 26, 2010
    About half of our warehouse equipment is battery, other half propane. Those forklift chargers are huge, generally 200A @ 36V and you wouldn't even want to imagine what shorting out the battery might do.

    Once saw a mechanic, in a hurry, change a battery but the wrench he chose was too long. It slipped, welded itself to the terminals and was white hot when I started running. Battery was of course spewing out hydrogen and when the wrench finally melted through the sparks set it off. Lucky the car was outside, after a huge pop there was battery and acid all over the parking lot.
  10. Nik

    Well-Known Member

    May 20, 2006
    I was taught that AC tends to throw you clear due muscle spasm, while DC tends to weld you to the contact. Either way, you only need 40~~50 mA to do yourself serious harm if the current path crosses your chest & heart. Like the folk who die when a cricket ball or base-ball hits their chest at the wrong point in heart-beat, you, too, could be unlucky. Treat live-wires with the respect due a passel of rattlesnakes. If you can, have an current-balance breaker in the line...
  11. nsaspook

    AAC Fanatic!

    Aug 27, 2009
    The only good thing about working with 80kV+ VDC 100mA power supplies on a daily basis is that you will never touch anything to grab on. It will reach out and get you, sending your body flying across the room. This has saved at least 2 people I know. Lesson learned, even with three layers of interlocks still use the grounding stick (EVERY TIME)