Getting complacent

[Doc]

I just had a little wakeup moment whilst working on my little RGY projector.

I had the rig projecting a yellow circle whilst I was tweaking the dichro. My left hand was resting on the chassis and I was adjusting with my right, whilst observing the projection.

Blat!! The index finger of my right hand dropped square on to the live rail of the green PSU; sticking 240v right across my chest.

It's been a while since I had the pleasure of a 240v 50hz, direct to ground shock and I can confirm that it still hurts as much as I remembered.

The stupid thing is; I have spent many many hours playing with and near really high voltages whilst playing with tesla coils, Jacobs Ladders, VDGs flybacks, etc etc, and never been bitten, because when you are playing with HV; HV safety is at front of your mind.

It is very easy to trivialize household line voltage when it is not the immediate subject of your tinkering.

Please forgive me for preaching to the converted and teahing granny to suck eggs, I just thought I'd share my blonde moment, it might save somebody from a painfull shock, burn or worse.

Moral:

The old rules are there for a reason.

1. Never, ever get complacent around line voltage
2. If you *need* to work near line voltage; use one hand and place the other in your belt loop/pocket etc
3. Don't work alone
4. Use an RCD
5. Listen to your own advice

[flecom]

The index finger of my right hand dropped square on to the live rail of the green PSU; sticking 240v right across my chest.

bigger issue is why is this stuff exposed? you should have some sort of cover or other insulating stuff on anything thats live... thats why im not a huge fan of these cheap chinese switching power supplies with exposed terminals, very unsafe

[Doc]

When I worked for Audi and we had a customer that was the root cause of the "problem" we used to say to them "it's the nut holding the wheel sir"

I see your point about the protective cover, but where do you stop?

I believe the problem in this case was purely me being downright stupid. I personally think that the whole health and safety concept has gone too far.

When the lid is on the projector; there are no live terminals exposed.

I was careless, I got bitten.

[MarioMaster]

Yeah I was wondering why you have exposed mains so close to a dichro on the optical table?

[Banthai]

Doc said

Please forgive me for preaching to the converted and teahing granny to suck eggs, I just thought I'd share my blonde moment, it might save somebody from a painfull shock, burn or worse.

Phew close call ..... well at least the plus side is you had a doctor in the building

i remember about 20 odd years ago i was in my workshop .... talking to some buddys holding a PSU pcb .... wired to a "mains safeblock" when someone picked up there coffee of the bench ... and knocked the safe block top closed .... which powered up the PSU and my hand holding it ....

my grip tightened and i stood there making a "GEEEEEEEEEEEEEEEEEEEEEEE" sound for about 15 seconds before they realised that it was not a joke .... and i could not move

someone then just tugged the cable to pull the psu from my hand ....

not an experience i would want to go through again

i understand your pain buddy

all the best ... Karl

[Doc]

Yeah I was wondering why you have exposed mains so close to a dichro on the optical table?

1. The whole projector internals occupy an area slightly larger than a VHS tape.

2. I have big hands.

[danielbriggs]

Doc:
http://www.youtube.com/watch?v=2a4gyJsY0mc

Nuff said...
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(sorry - someone had to!)

[mikkojay]

Ouch! Glad to see you lived to tell the tale...
When I was an avionics tech in the USN, I saw one of our guys accidentally bridge a bus bar with a pair of needle-nose pliers (3ph 115 @ 400Hz ) One part of the handle glowed and melted in about .5 secs like a toaster wire times 10,000- luckily he didn't blow his hand off.
-Mike

[Xytrell]

Using a ground fault circuit interrupter (or residual current device as it's known elsewhere) isn't a bad idea either.

[flecom]

I see your point about the protective cover, but where do you stop?

well, personally my projector is almost always (and always will be) uncovered, so i try and cover all exposed main connections always, either by using connectors or electrical tape/plastic covers of some sort... additionally i try and minimize the number of PSU's in the system (aka not one per laser and an extra one for the galvos etc etc) minimizing the number of connections needed for mains anyway..

i do feel you in trying to make a small projector, I've kind of given up on that hope lol