New product possible shock hazard? - Page 1
Forum section: electronics / general

author: peteb2
author_rank: Regular Contributor
timestamp: April 16, 2016, 07:33:51 am
content: This is a quick question on electrical safety. Yesterday I was handed a brand new LED flood light (used during video filming) to mod so a battery pack can be clipped to it rather than having to connect a long cable from the battery into the XLR-4 male DC connection on the lamp. The lamp has a mains cable permanently attached as well so it can be run off anything from 100Vac to 240Vac.When i opened the unit i found the standard rocker DPST power on/off switch to be wired so Mains uses one contact set, the other has the 12Vdc from the XLR-4 connector on it... (!!!!!!)I have never seen this kind of practice (usually a DPST mains power switch breaks both Active and Neutral that feeds the power-supply stage and absolutely nothing else). I am fairly certain this LED flood light will be classed as unsafe, (therefore unsaleable) in my country but won't know for sure for a while. I'm questioning if anyone else thinks the way this device is wired is ok practice...So... in the pic below you can see the black ring-marked wires, one coming from the screw terminal block (Active 240Vac) to the switch and then another that feeds off to the power supply (out of shot). The other un-banded wires on the DPST switch are the 12Vdc leg from the XLR-4 male connector and then it feeds off to the controller circuit.In any setup if you are using the lamp on 12Vdc, no problem but its when you have AC Mains connected becuse there's less than 1/8" (3mm) gap across the spade terminals that COULD connect out to the touchable pins on the XLR-4 dc socket...The lamp could (will) end up being used in some rough-as conditions, rain etc or some foreign body fall in there like a metal screw and someone is gonna cop a shock if they are using Mains... I dunno, just my thinking maybe this is totally OK in other countries....So, yeah... love to hear your feelings on this and apologies if this kind of post is in the wrong place...i am a noobee here)...The switch is similar to:http://nz.rs-online.com/web/p/rocker-switches/5332986/

author: Kilrah
author_rank: Unknown
timestamp: April 16, 2016, 09:01:38 am
content: Need more info about how that lamp is made. From what we can see of the he simple wiring suggests you should never have both the 230V and the 12V connected to it at the same time in the first place.

author: SeanB
author_rank: Super Contributor
timestamp: April 16, 2016, 09:08:01 am
content: Should have used the fully shrouded spade connectors, but you can simply slip a small piece of clear heatshrink over the lugs and shrink it on, which will reduce the foreign body issue. You do not have to switch both active and neutral ( though it is better in some countries with no defined socket outlet polarisation, but not in AUS/NZ) so using it only as a single pole switch is fine. Used so they only need a single power switch, and not a separate mains and battery switch, which could lead to the built in power supply trying to charge the battery by accident with the lamp off.As to clearance, that is fine, as the switch internally in any case has to pass an insulation test of 1kV or so between the poles, so it will do fine there, especially as the chassis is well earthed as well.Just hope that nobody replaces that switch with an illuminated version if it fails, as then you will be powering the internal neon from the line to the 12V supply.500uA or so, might survive, might degrade something, but will not trip a RCD.

author: rch
author_rank: Regular Contributor
timestamp: April 16, 2016, 09:58:30 am
content: I agree shrouding of the spade connectors is the main obvious lack. But in the UK I have a feeling that earthed equipment is supposed to have a double pole mains switch. They perhaps should have used a 3PST switch though I expect it would have cost more than having a separate 12V switch.

author: peteb2
author_rank: Regular Contributor
timestamp: April 16, 2016, 12:23:35 pm
content: Thanks for the replies so far.... Yes I believe it to be a truly piss poor design approach to combine a low voltage DC path through one half of a cheap NZD$4 DPST switch and MAINS Vac through the other half. This brand new LED professional production luminaire (spot light) will be used in harsh situations, could get wet and will be knocked around. I wonder just how close the internal mechanical switching parts are inside the tiny switch and what actual isolation there is other than air and that it would be very easy for the +ve of the touchable male pins in the 12Vdc XLR-4 connector to go Live. There isn't even a Mains fuse. In my country things are very strict when it comes to Mains Electical Safety but increasingly equipment arrives onto the market that for all intended purposes isn't really that safe...

author: station240
author_rank: Unknown
timestamp: April 16, 2016, 02:24:49 pm
content: I also see a shock risk should anyone repair this in the future and put the unlabelled spade connectors onto the switch in the wrong order.I'd start by installing fuses on the mains/12V inputs, and a 20V Varistor on the 12V side. Should anything bad happen, the fuses will blow.

author: amyk
author_rank: Super Contributor
timestamp: April 16, 2016, 03:44:10 pm
content: If the switch is rated to handle 240VAC, it should be fine with 12V.

author: Someone
author_rank: Super Contributor
timestamp: April 16, 2016, 11:46:14 pm
content: I'm not sure if anything has changed since the copy of 3100 I have to hand but it fails 4.1.2, Segregation of internal wiringThe takeaway for the standards is that under single fault the device should remain safe. This specific problem is that if the mains cable were to come loose in service (break off at the crimp even) then no matter where it reaches it cannot be allowed to cause a hazardous condition to exist.Fails Australian compliance under my reading of it.

author: Ian.M
author_rank: Super Contributor
timestamp: April 17, 2016, 12:05:53 am
content: Just about the only way to make it safe would be to remove the mains wiring from the switch, and wire it direct to the mains in terminal block, then patch in that switch pole to switch the output of the PSU module.IMHO you should report it as a hazard.

author: rch
author_rank: Regular Contributor
timestamp: April 18, 2016, 11:54:06 am
content: Quote from: amyk on April 16, 2016, 03:44:10 pmDC voltage and current ratings for switches are much lower than AC voltage and current ratings for a similar switch. And any reactive current/voltage on switching the DC has to be allowed for. It is not by any means certain that a suitable 240V 5A switch will be rated for the DC supply here.