How does one actually get a shock from DC? For example I've put my fingers between an air spark from a flyback transformer on a humid day for a second or two, and felt nothing. Estimated 40k volts. On 27 March 2015 at 13:36, RussellMc wrote: > *Relevant summary: * > > In worst case conditions 10's of *micro*amps applied to the heart can cau= se > ventricular fibrillation and death, > > Unusual but not wholly unlikely situations may occur in 'real life' where > *much* lower than usually expected voltages and currents can cause death. > > ________________________ > > > The post at the end just reappeared in response to a search re "testing a= n > ac motor" posts. > I copy it below untrimmed. Original subject line was "[OT] Danger of DC > Power Supply" > > This is worth added comment as I have recently encountered an article tha= t > provided new (to me) information on the minimum amount of current which m= ay > kill in worst case cases. I have never been very happy with some of the > commonly offered advice re "safe" currents and have been aware of the fac= t > that some people die in situations where currents seem to have been much > lower than might be expected. > > *Death MAY occur with heart currents in the 10's of micro-amp range.* > > *That's MICRO-amps.* > > The "trick" is that this is HEART current - currents this low usually onl= y > apply to situations where: > > *From PDF below:* > > there is a high conductivity path into the heart itself - > maybe a metallic conductor for instrumentation or a saline fill= ed > tube. > > *From powerpoint presentation below:* > > Patient with *breaks in skin like abrasions, wet dressings*, pacemakers, = or > monitoring lines connected to a transducer > > > Note that the references below provide "statements of fact" without > supporting data, and several have at least one author in common. > Hoever, given the sources and contexts, Occam suggests that taking note p= of > what they say would be highly advisable. > > __________________ > > *See: "Electrical Safety in the Operating Room ..."* > > Populist & pretty > > > http://danieljohndoyle.com/uploads/3/0/7/7/3077522/ccf_rc_electricalsafet= yintheoperatingroom_rev_2011.pdf > > Paper > > > http://journals.lww.com/anesthesia-analgesia/Fulltext/2010/06000/Electric= al_Safety_in_the_Operating_Room__Dry.1.aspx > > > *Powerpoint * > > > http://www.uiowa.edu/~medtest/or_reference/ELECTRICAL%20Safety%20.pdf > > *Relatedish* > > > https://www.google.co.nz/search?q=3D%22electrical+safety+in+the+operating= +room%22&biw=3D853&bih=3D571&tbm=3Disch&tbo=3Du&source=3Duniv&sa=3DX&ei=3DE= p4UVYOHLOOmmAXFqYGwBQ&ved=3D0CDIQsAQ > > > *Video - 37 minutes* > > https://www.youtube.com/watch?v=3DQ-51Igy_J9A > > > _________________________________ > > *PRIOR: two edits in [square brackets] added* > > > On 21 November 2013 at 23:39, RussellMc wrote: > >> What kills is current through heart muscle locking >> [affecting] >> muscle and preventing >> [normal] >> heart action. Removal may or may not still kill - if heart fibrillates >> (noisy electrical chaotic shimmer mode) rather than restarts you 'have >> problems'. >> >> A <=3D 30VDC power supply will generally be safe. It's best to avoid >> contact if possible, NOT work in damp conditions and not have a situatio= n >> where it can ever be applied across your chest. eg carrying a 24V lead a= cid >> battery of any size with contacts against your chest or against a shirt = if >> you are sweaty COULD be fatal but is unlikely to be. >> >> 1. Rub your chest with saline solution and apply two 30V electrodes to >> skin across heart or nearby and it has a good chance of killing you. >> 12VDC applied via electrodes across a (convict) volunteers chest has >> resulted in death. This was unexpected and in spite of resuscitation >> attempts. >> >> 2. Stand in salt water with bare feet with one 30V terminal in water als= o >> and brush other terminal with dry hand and you will PROBABLY not feel it= .. >> >> 3. Not many people know the following. I have a friend who experienced >> this with 12V while flounder fishing with a pole lamp with a metal pole.= An >> unexpected lockup experience. >> As in 2. above but add saline to hand that grasps and grasp terminal so >> there is hand - foot conduction and you may get muscle lockup in hand so >> you cannot let go. This MAY kill you but that is very unlikely (providin= g >> somebody unlocks your hand so you can wander off. >> >> 4. Generally under almost any circumstance you would normally meet you'd >> not feel 30V or have adverse reactions BUT as above there can be excepti= ons. >> I'd regard 12V and below as essentially super safe, 24V as safe with a >> soupcon of care and 30V as hardly worse. >> >> Work on a Telco wiring frame with 50V and no care is usually taken to no= t >> make contact and no feelings of electricity present when you brush >> contacts. BUT on a high humidity day you start to get annoying tingles >> across the nuckles. >> >> 100 VDC will happily kill you in many cases BUT may not. I'd not grab tw= o >> 100V terminals for any reason that comes to mind. >> >> AC is generally safer than DC at any given voltage as your muscle >> cyclically relax allowing release. >> I have had perhaps dozens of 230 VAC shocks of various magnitude. >> Plus a very few at 1000+ VDC >> I try to avoid all such these days and have not had a decent shock for >> some decades AFAIR. (A good shock across the head aka ECT may clear shor= t >> term memory, so one can never be sure :-) ). >> >> >> >> >> Russell >> >> >> On 21 November 2013 22:59, Lindy Mayfield wrote= : >> >>> Up until now, my understanding of electricity and safety has been prett= y >>> basic. Batteries around the house, 9v etc, the development boards, I'v= e >>> been playing with, and so on, I don't worry it can hurt me. If it is >>> household 220 v AC, then I treat it with respect. Even if I do know t= he >>> light switch is off, I still test it with a multimeter to be double sur= e. >>> >>> But I don't know what comes out of this power supply. It goes up to 30 >>> volts and 1 Ampere. So as an example, just touching wires on motors li= ke I >>> would with a battery, can this thing be set high enough that I could ge= t a >>> (bad) shock? >>> >> > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .