studio light that's my first project and I don't want to kill myself - Page 1
Forum section: electronics / beginners

author: tavit
author_rank: Newbie
timestamp: July 26, 2011, 12:24:04 am
content: Hi everyone, this is my first post on forum and first project ever. i wanna build study light, it's look really easy but I'm nor sure and It would be embarrassing die on first projectSo, I'll use 4 lamp sockets, 2 switches and one cord. Each switch have to light 2 light boles. I figure out that for 2 sockets I'll connect 1 switch and 2 switch will be connect with cord. Is that will be work?

author: IanB
author_rank: Super Contributor
timestamp: July 26, 2011, 04:32:47 am
content: It's normally recommended not to use mains voltages in the first projects you do. It is much safer to stick with battery power.If you want to wire up some lights and you are unsure how to do it, you need to find someone near to you to instruct you. Do you know anyone who is an electrician or someone experienced in electrical wiring? You should not undertake such a project if you have any doubts about how to do it safely.

author: Simon
author_rank: Unknown
timestamp: July 26, 2011, 05:44:22 am
content: ditto, if unsure when dealing with lethal voltages: DON'T.you can regularly blow stuff up that runs on 12-24V as that voltage cannot kill you and at worse you may start a fire if you leave a project unattended. but 240V will kill before you even know what happened. I have have my life saved a couple of times by an RCD, this was not because i miswired something but because I was working on something someone else had wired up badly, even with an RCD in place you can get a shock that will shake you up for an hour.If you really do do this make sure you use an RCD.

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 26, 2011, 05:49:14 am
content: Quote from: IanB on July 26, 2011, 04:32:47 amthats your teacher telling. no its perfectly safe working with home mains. a good first lesson is to touch a life wire. that was me when i was like 7-9 years old.d 2nd good lesson is to connect directly 12v rated bulb to mains wire, make sure you wear your google if you dont want to risk losing your eye.

author: Simon
author_rank: Unknown
timestamp: July 26, 2011, 05:50:53 am
content: Quote from: Mechatrommer on July 26, 2011, 05:49:14 amyou need to check into your local nut house very fastunless your a cat with 9 lives because you and me and the OP only have one life

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 26, 2011, 05:54:49 am
content: Quote from: Simon on July 26, 2011, 05:50:53 amthat means i've been dead for so many times. latest is few days back when i disconnected the UPS power plug (while the unit is ON) and touch the power plug pin.

author: Simon
author_rank: Unknown
timestamp: July 26, 2011, 05:59:10 am
content: are you on 240 V or 110 V. either way it is not clever and you should not be advising new comers to do dangerous things, or else on your head be it !

author: gregariz
author_rank: Frequent Contributor
timestamp: July 26, 2011, 06:50:48 am
content: Quote from: Simon on July 26, 2011, 05:44:22 amThere was actually a case of someone being electrocuted at 24 or 32 volts (can't recall) over an extended period of time. They were pinned under a heavy piece of equipment and it took a while I believe..... just sayin

author: Bloch
author_rank: Unknown
timestamp: July 26, 2011, 09:49:13 am
content: I cant find the links butDC are the worstIt is not the voltage that is dangerous butcurrentover 30 mA is bad ... over 70mA really bad :-) .... Over 300mA then call 911 before if you want a chance to live !!First test thehttp://en.wikipedia.org/wiki/Residual-current_deviceone time a year (at least)Turn off all circuit breakers before open / touch / fix / ...Here are a great page sadly for you i Danish but i did put it in translationhttp://translate.google.com/translate?js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&sl=da&tl=en&u=http%3A%2F%2Fcubus-adsl.dk%2Felteknik%2Fcases%2FQuoteWell Some do-it anywaySo I think it is better to educate.

author: ejeffrey
author_rank: Super Contributor
timestamp: July 26, 2011, 10:19:47 am
content: Quote from: Bloch on July 26, 2011, 09:49:13 amCan we please, please, please stop repeating this nonsense! Current and voltage are related by ohms law. A 12 volt car battery can source hundreds of amps, yet is no electrocution risk (but certainly can be a fire hazard!). It is true that many high voltage sources, particularly electrostatic generators (i.e., van de Graff generators) have high enough impedance that they pose relatively little danger -- the short circuit current is too small to cause damage. However, there are far more examples of high currents at safe voltages than high voltages at safe current levels.

author: Bloch
author_rank: Unknown
timestamp: July 26, 2011, 11:32:00 am
content: Quote from: ejeffrey on July 26, 2011, 10:19:47 amYou heart dont care one bit on voltage....That is why it is a law here in denmark to have ahttp://en.wikipedia.org/wiki/Residual-current_deviceI do some times work with 3*690Vac - 700A so I have been trained in that can be dangerous.The heart do not care i the current comes from 1,5V or 24Vdc powered equipment. Or the mains.The problem with DC is that the hart stop working. As for mains (50/60HZ) it will pump at that fixed rate. So if some one hangs in the wires for a long time...... I know that i would prefer the ACQuote from: ejeffrey on July 26, 2011, 10:19:47 amThe current i talk about is the current that goes through the body(heart). And in that case i do not age with you at all.

author: PetrosA
author_rank: Frequent Contributor
timestamp: July 26, 2011, 11:44:53 am
content: Quote from: Mechatrommer on July 26, 2011, 05:49:14 amI fuckin' give up.

author: vk6zgo
author_rank: Super Contributor
timestamp: July 26, 2011, 12:18:00 pm
content: Quote from: Bloch on July 26, 2011, 11:32:00 amOhm's Law,my friend!I =V/R----normally the resistance of the human body is sufficiently high that low voltages cannot cause a current flow great enough to cause injury.In medical systems,in many cases the best possible connection is made,in order to detect extremely low level signals,so that the acceptable voltage across the contacts of these systems is reduced,-----BUT the current still is I=V/R!!Another falsehood which is widely believed,is that low voltage sources which are capable of supplying large amounts of current through low resistances can in some mystical way force large currents through the relatively high resistance of the human body.Mechatrommer's comment was,of course,in jest,but as nobody else got the joke,it is doubtful that the OP would understand his humorous intent either.To the OP:-The 240volt mains supply is extremely dangerous & is quite capable of killing you!!For that reason,get advice from some knowledgeable person,face to face.If in any doubt,change your design to use low voltages----You can make quite bright lights using High Intensity LEDs.VK6ZGO

author: ejeffrey
author_rank: Super Contributor
timestamp: July 26, 2011, 01:01:34 pm
content: QuoteThis part is almost completely wrong. First off, your heart "beating" at 60 Hz is called ventral fibrillation and it leads to heart stoppage in seconds and death in minutes. The relationship between frequency and heart danger is complicated and mostly academic. All forms of high voltage + high power circuits are dangerous, all low voltage circuits are not. DC voltages tend to cause paralysis of your skeletal muscles while AC tends to cause spasming. The later may cause you withdraw from contact faster than even a normal reflex. Under prolonged contact, AC is somewhat more likely to cause fibrillation than DC, and in high DC currents are used in cardiac defibrillators to restore normal heart function. At high frequencies, skin effect begins to play a role and the danger of fibrillation decreases. RF is more likely to cause life threatening burns than to electrocute you.

author: Bloch
author_rank: Unknown
timestamp: July 26, 2011, 01:11:23 pm
content: Greate advise.Quote from: vk6zgo on July 26, 2011, 12:18:00 pmI know that. But some still think that this is just battery powered then no problem.(12Vdc)

author: Bloch
author_rank: Unknown
timestamp: July 26, 2011, 01:57:57 pm
content: Quote from: ejeffrey on July 26, 2011, 01:01:34 pmThank you for the correction. Nice to lean some thing new.Quote from: ejeffrey on July 26, 2011, 01:01:34 pmThat is you def. on high voltage ?This that i learned.low voltage (50–1000 V)high voltage(1000V - 5000V)I know it may be not be called the same all over the world. ( But then i go to ABB to buy a 3*400Volt contactor then it is under Low voltage)As for that hurts most ...(400watt HF ssb)http://www.peel.dk/SP/T2031.htmlWell from the very big and very angry fisherman ...... well alot230 Vac alot400 Vac Don't want that again !Big Sony CRT tv 36inch i think. I could not use the arm for the next 6-8 houers !! and i got a small hole in the thick skin (thumb finger) and it took many months for it healed properly

author: Zero999
author_rank: Super Contributor
timestamp: July 26, 2011, 05:48:33 pm
content: Quote from: Bloch on July 26, 2011, 11:32:00 amThat's not true.At mains frequencies the current required for ventricular fibrillation is lower than that of DC. Low frequency AC is generally more dangerous than DC, on one level it's common sense, AC has 1.414 times the voltage, current and double the peak power but there are other physiological reasons for this It's only at higher frequencies (above around 20KHz) when AC becomes less dangerous because the nervous system doesn't respond to it.Here are some more links:http://books.google.co.uk/books?id=B0aPhJn0YcAC&pg=PA963&lpg=PA963&dq=let-go+current+shock&source=bl&ots=eELpQzCycv&sig=xMzkz9AeJWLghhYrWU7B4Sa4VS4&hl=en&ei=SejpSajnJcONjAf64LibCg&sa=X&oi=book_result&ct=result&resnum=5#v=onepage&q=let-go%20current%20shock&f=falsehttp://www.pat-testing.info/electric-shock.htmhttp://www.esdjournal.com/techpapr/elechazd/ehaz.htmhttp://www.health24.com/medical/Condition_centres/777-792-2557-2577,15144.asp

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 26, 2011, 06:19:29 pm
content: the 1st picture is battery powered. no its not safe, dont play with battery. i believe the poor OP has enough entertainment, from eevbloggers, i believe what he want is some combination of in 2nd picture. i was sayinghomemains, not industrial above 240V. if you play around with 1000V in your first project then you are fool.

author: IanB
author_rank: Super Contributor
timestamp: July 26, 2011, 08:38:40 pm
content: Quote from: Mechatrommer on July 26, 2011, 06:19:29 pmWould youpleasestop being an idiot? Home mains, whether 120 V or 240 V, is plenty able to kill you. There are far too many dead people electrocuted by home mains as testimony to that. Sure, there are many of us who have done dangerous things and survived, but "I did a dangerous thing and survived"does not mean"the dangerous thing is safe because I escaped when I did it".To do mains wiring safely you need someone who knows to teach you how to do it. If you don't know what you are doing you shouldn't try.

author: Unknown
author_rank: Unknown
timestamp: July 26, 2011, 10:25:22 pm
content: Quote from: Bloch on July 26, 2011, 01:57:57 pmQuote from: IanB on July 26, 2011, 08:38:40 pmCome on guys a bit of reality please! It's current through the body that can and will kill. The comparisons between a 240V shock and a 415V are laughable. If your body had experienced anthing like the full potential you wouldn't be here bragging how you survived. To cop 415V you'd have been across two live conductors with zero other resistance, I doubt you'd have survived.Electrical potential holds not workplace distinctions the potential to ground is going to be the same at home or in the workplace and apart from RCDs a human body isn't going to trip the current protection at either location.As an electrician in a past life I've copped more than my fair share of tingles, zaps and painful belts from mains supply. The hurt and the can kill, while I expect to cop (but strenuously try to avoid) other zaps at times, I can tel you it is very different from getting hooked up, something few survive.Think about it for a second, Ohms law still applies, and while you may have come in contact with mains voltage, your body was most likely only part of the total circuit.Current I = [V mains]/[R toolgrips] + ([R body] + [R damp gym socks] + [R shoes] + [R carpet] + [R building structure]) . Unfortunately for the curious I've never managed to take potential readings during moments of electrocution but the theory still applies regardless.Back to the OP, I will not try to dissuade you from taking on a medium voltage project, if that is what you wish to build, ask the questions , do the research and build it. But do take serious heed of all the warnings above and do do the following.- HAVE SOMEONE SKILLED (preferably qualified) CHECK YOUR DESIGN- HAVE SOMEONE SKILLED CHECK YOUR WORK PRIOR TO PLUGGING IT IN- NEVER FOR A MOMENT TINKER WITH YOUR PROJECT WHILE IT IS PLUGGED INTO THE MAINS- SEEK THE SAME LEVEL OF ASSISTANCE SHOULD YOU DECIDE TO DO ANY CHANGES TO YOUR PROJECT.Regulations vary from country to country and you should respect those of the country you are in and remember always that anything above ELV can kill and that ELV can be made to produce higher potentials that can kill. Don't be dissuaded from building something but ensure what you are building is safe.If you need help here provide more detail on your pet project and heed the warning that people offer. Expect to be questioned and to be told to look things up.

author: IanB
author_rank: Super Contributor
timestamp: July 26, 2011, 10:40:09 pm
content: Quote from: Uncle Vernon on July 26, 2011, 10:25:22 pmMost often, no, that's not quite the case. It's current through theheartspecifically that is going to kill the amateur electrician at home. The heart is a complex organ that depends on delicate electrical rhythms to keep working properly. It only takes a tiny nudge at just the wrong time to throw these rhythms off and then you can have a heart attack and die. There have been documented cases of people who have had an electric shock, thought they were OK, but dropped dead the next day. No, this is not a joke, it has really happened.I know we have all been zapped. I have been zapped by 240 V as a foolish teenager more than once. Yes, we tend to get blasé about it. But the reason I am alive is not because 240 V is harmless, it is because I waslucky. Just remember that. Each time you survive an electric shock you have used up one of your lives. One day you may not be so lucky.

author: Unknown
author_rank: Unknown
timestamp: July 26, 2011, 10:59:01 pm
content: Quote from: IanB on July 26, 2011, 10:40:09 pmCurrent through any part of the body is capable of upsetting your heart. It does not require direct current path through the chest or abdomen. Most electrocutions are via the hands and arms. ANY BODILY CONTACT IS POTENTIALLY LETHAL.QuoteWhile the conductors you contacted may have been at 240V the reality is that you probably had much less than that potential across your body. Regardless, it was a potentially lethal situation!QuoteI sure as hell don't! Odds on, I will receive shocks again in my work. Any of them can be lethal! I will do everything realistically possible to minimise the risk.QuoteAgreed. The risk is there and is very real.QuoteMany lives? That's bollocks we only get one. One chance one shot. Any mains electrocution can end that life. "Many Lives" is the stuff of old wives tales.

author: vk6zgo
author_rank: Super Contributor
timestamp: July 27, 2011, 12:58:34 am
content: I think many people have picked up on this probably originally jocular saying & invested it with meanings that it never possessed.Another similar saying,which is taken far less seriously is:-"It's not the fall that kills you,it's the sudden stop when you hit the ground".Just as with this saying,where you need the fall before you can have the "sudden stop",youneed the voltage before you can have the current.If in the case of the fall,you had a parachute,(air resistance),you wouldn't have a "sudden stop,& similarly,if you have sufficient electrical resistance in series with the voltage source,you will have a smaller current.One other thing that is confusing,is that as Technicians & EEs,we normally think of voltages up to around 48 volts or so as "low voltages",& 120 v & 240 v as being "high voltages",but the Electrical trades have a very different definition where say,48 volts is regarded as Extremely Low Volts,& 240 v,say is Low Volts.(I don't have the definitions to hand,but others probably can quote them).Yes,many of us have been "bitten" by 240 volts & gotten away with it,but as IanB says,we werelucky.Plenty of Americans have been killed by 120 volt mains too!VK6ZGO

author: Kozmyk
author_rank: Regular Contributor
timestamp: July 28, 2011, 01:55:02 am
content: Don't be too sure that electrocution or shock damage can't be initiated from a low voltage supply 12V-24V. The human body'sExternal Resistanceis usually high enough to prevent enough current flowing to be dangerous.BUT some people's skin resistance can be very much lower than average, just as some have a much higher resistance than normal.I worked with a guy who could happily hold neutral in one hand and 240V live in the other and not even feel a shock! His skin resistance was near 10MR.Very dry skin.DON'T try that at home kids.Futhermore, the body'sInternal Resistanceis much lower and so if contacts pierce the skin or touch open wounds then the danger is increased.Electrolytes such as salt solution, battery acid can improve contact with the body, increasing hazard.Fitters in the lorry garage I worked at for a while got some nasty 24V belts from handling batteries with wet hands and a bit of spilt acid.Similar 12V shocks are much less common but not impossible when conditions conspire with Ohms Law to increase the current.Anyone in the trade will have had occupational "belts" to some extent or another.Most of them we pass off with a curse and a yelp as an occupational hazard.My worst experience was as a musician in a recording studio that had just been rewired.I handed a mic stand to my mate and we got the full force of the 240Vmains across us, both hands and feet.The wall socket my amp was plugged into had live and earth reversed (maybe the whole branch) and so there was no fuse to blow until the company fuse, this was in the days before RCDs.My mate was dropping and my consciousness was receding, vision going away down a long tunnel. A bass guitar string melted where it contacted my mates guitar as they banged together, sparks flying.I was being beaten up from the inside courtesy of muscle pairs fighting each other from the AC.From somewhere I got some willpower and with a roar "NOOOoooo!!!" I over-rode the shocks and broke free, snapping a heavy leather guitar strap in the process.Death averted ... but only just.We were whisked round to a doctor friend who checked us out, gave us hot tea No sugar, and a "herbal" cigarette each for the shock.That's my best electrocution story.Maybe we should start a thread "What's the worst shock you've ever had?"

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 28, 2011, 02:35:28 pm
content: Quote from: Kozmyk on July 28, 2011, 01:55:02 amyour experience was not during tinkering project, but just a result of bad wiring practice made by others, you are the victim of their stupidity. during project making, one suppose to have higher level of alert and carefulness compared to when using electrical appliances that we thought is safe. my bro wrapped power cord of soldering iron around his wrist and the rubber shield got torn at some part in the cord. so while soldering, the exposed copper contacted his skin and the unit got thrown few meters away, luckily the cord didnt stuck on his wrist otherwise we know what happen. this is an example of bad product safety and ignorance and stupid practice (wrap mains cord around wrist/body). if the cord got no torn or strong shield, this will not be happening. death report i've heard only involving accidental situation like this, but i never heard people dead because just testing the "home" mains by touching it with finger.

author: Zero999
author_rank: Super Contributor
timestamp: July 28, 2011, 06:20:08 pm
content: Quote from: ejeffrey on July 26, 2011, 01:01:34 pmThat's not true, the skin effect has no role in protecting one from electrocution. The skin depth of human flesh at say 200kHz is very deep as it's a poor conductor and is non-magnetic, the same is true even at GHz frequencies, otherwise microwaves wouldn't penetrate the surface of meat to cook it below the surface.The protection against shock comes from the fact that the nervous system doesn't respond to frequencies higher than around 20kHz.QuoteAn arc could also connect you to dangerous a lower voltage, DC/lower frequency energy source which is common in a Tesla coil.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: July 28, 2011, 07:58:20 pm
content: Quote from: PetrosA on July 26, 2011, 11:44:53 amNo no, do not do it ...Be brave .I have read and more stupid things than that.Some one was interested to measure the amperes in the output of one transformer operating at 8KV.I had to tell him that he can do that from the input of 220V.Now I feel like to was a lifeguard of Baywatch (TV series) I save him.. LOL

author: IanB
author_rank: Super Contributor
timestamp: July 28, 2011, 10:42:43 pm
content: Quote from: Kiriakos-GR on July 28, 2011, 07:58:20 pmWhich reminds me of one of the classic mistakes you can make when working on a step down transformer, for example one which steps down from 11 kV to 240 V. You isolate the 11 kV primary side to make the transformer safe and go to work. Only to be surprised when the transformer is still energized at 11 kV and kills you. (Because another circuit may energize the low voltage side and turn it into a step-up transformer. Always isolate all windings on a transformer before thinking it safe.)

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: July 28, 2011, 11:56:59 pm
content: Well we starting to have a real problem with all those high voltage Tesla coils.Many young ones loves the sparks.And they fantasize about making an such device.And so they jump in forums asking questions like:What it will happen if I try to measure 8KV with my DMM ?Answer:You will be Toast , you need a special HV probe 15KV or 40KV.I do not like to spent that money for the probe, its just an experiment not a job.Answer:There is no answer ...Few months back we had a fever about blown DMM, thanks God as community we get over it.Today the newexcitingidea are the Tesla coils, more sparks and more silly questions.

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 29, 2011, 04:12:08 am
content: Quote from: Kiriakos-GR on July 28, 2011, 11:56:59 pmwhose fault? if i have to find someone to blame, nobody else other than Mr Tesla (or simon the photoinductionist) or even mikeelectronicstuff!he got that cool jacob ladder in his Fluke LVD2 review. and there's one section overlay with text "DONT DO THIS" with his HV variac, the funny thing is he just did that!sorry mike, i didnt mean to, but its just slipped away.

author: jahonen
author_rank: Super Contributor
timestamp: July 29, 2011, 11:07:48 am
content: Quote from: Kiriakos-GR on July 28, 2011, 11:56:59 pmDo you mean something like this:Regards,Janne

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: July 29, 2011, 11:22:23 am
content: Quote from: jahonen on July 29, 2011, 11:07:48 amWhat the F*** is this ? LOLThe most wild thing that I had ever did , was to touch the anode with a single finger of one tube that was transmitting in FM band with 40W of power,and 310 DC on the anode, coming from 220 AC directly from the mains = Plus active phase .

author: Unknown
author_rank: Unknown
timestamp: July 29, 2011, 08:31:23 pm
content: Quote from: Kiriakos-GR on July 28, 2011, 11:56:59 pmIf you got a good DMM and probes, you'll likely survive. A CAT III 1000V or CAT IV 600V rated meter is designed to stay safe under 8kV transients. Granted, this is a peak value, and not continuous, but the chances of the meter not blowing up are fairly good. Doesn't mean that it's a good idea at all of course. For low energy circuits (eg. CRT), a cheap HV probe like you suggest is sufficient. Otherwise, you need more specialized and expensive tools.Quote from: Kiriakos-GR on July 28, 2011, 11:56:59 pmIf you can't do something safely, don't do it at all.