Voltage at light switch when turned off

[shonkster]

This is more of an electrical question rather than electronics, but I'm sure someone would know....

I've got these 240v LED globes which can switch between Cool daylight and Warm White....
If you turn the light switch off on then the globe will change colour. If you lead the switch off for more than 6 seconds it should default to Cool Daylight next time you turn it on...
What I've found is that this doesn't happen.... (the 6 second thing) I've been dealing with customer services who make the globes. They sent me globes which they tested before hand to confirm might globes aren't faulty. When I got the new ones same thing....

What I have found is that if I take the globe out of the socket for 6 seconds, then it will default to cool daylight every time... so there is something going on electrically which is preventing the globe from doing that 6 second count down

I did another little test... I measured across the light switch when its off....
With these globes I get about 195-201v across the terminals
With a normal 60W globe I get 240v across the terminals
With another brand stand cool white only LED globe I get about 135v across the terminals....

So is this indicating there is a bit of resistance present in LED globes?
Does this make sense to anyone??

Would it make any sense if my light switches are actually switching the neutral instead of the active? I don't have an earth reference in reach to compare the cable at the light switch and earth but I could probably make that happen if that is going to prove anything else?
Thanks

[ol' boy]

Yeah, there is a small amount of leakage voltage across a normal domestic switch.

In saying that, its only ever measurable with a sensitive digital meter
I used to refer to it as a ghost voltage, because if you added any kind of load, it disappeared.

Given the way your LED light auto select modes, this leakage voltage may very well be the problem.

As a test, add a resistive load across the same contacts.

Another option might be to use a 2 Pole Switch Mech, it switches both Active and Neutral at the same time.
(You can not switch the neutral as you suggested, only the active or both)

Good Luck

[ammlione]

Hi,
It may be safer to put the globe on a nightstand lamp or other portable lamp and plug/unplug quickly from the wall.
If it works, then you may need a different brand of switch or better, get an electrician to check your wiring.

Adding resistors to a mains switch without precautions can give you a nasty surprise.

Cheers

[koshari]

Google "capacative coupling" and all will become clearer. The switch wire going down to the switch is acting as a capacitor.

Very common. Generally makes led lamps glow very dimly or compact flouros strike momentarily occasionally.

[shonkster]

I wonder if there is an electrician who knows enough to troubleshoot this... they might say normal globes work, power turns on.. no problem I dont mean to say electricians are dumb but I just mean there are probably a lot out there who have done the theory years ago but never need to apply it so its forgotten... (me included in that).

There is no neutral at the switch so I cant switch both..
I have installed these lights in many rooms on different switches...
One of them has 5 globes connected to 1 switch... another has two way switching...
So I have different combinations of switches in different parts of the house all with the same issue.
I am fairly sure they worked when I only had one globe for testing...as i bought 1 light for testing before i bought more and rolled it out to multiple places.....(maybe i didnt test it enough)
Could these globes globes be doing something capacitive now that i have 8 of them through the house... I havent tried going back down to one...
The electrical cabling is fairly neat in this house in the roof. Maybe thats a bad thing though as they are all lumed together... maybe some induced voltage between the cables?
I do have 3 phase for air conditioner. . I dont know if the cabling for that is running near the other cables...
Thanks

[freakee1]

With most wiring (99.9999% of standard lighting circuit) you are switching the Active only (red wire is live and white wire goes to light) - and therefore have 240V at the light switch at all times (lets not worry about 2 way or 3 way). If you measure across the open light switch you are attempting to measure the voltage to neutral and with a standard globe you are including the globe as part of the circuit - you will get 240V across the switch and with the globe out you will get close to nothing. The globe makes the circuit. With electronic lighting you will find it is a complex circuit of electronics designed to reduce the voltage to a voltage that is used by whatever the device is. You don't have a clean resistive circuit to neutral (like the incandescent globe) and as such get a different voltages.

Now for your problem
I'm thinking that the electronics of the LED isn't seeing 0V and therefore not changing state from Warm white to Cool white, as for a solution you might have to look at rewiring as Oceanboy might have hit the nail on the head - switching both the neutral and active to the specific LEDs will give you a break in both Active and Neutral (and then lets hope you dont' have to worry about inductance)


or not worry about them




f

[cmangle]

In the states, voltage detected when switch is off can be(although not the only cause) attributed to what we call a "floating ground" (assuming the switch and wiring are in good/proper working order).

One cause is and unbalanced electrical panel that causes current flow on the neutral, another is bad grounding !

I don't know if this is the case with you, just trying to give a little more input!

[shred]

As a test, add a resistive load across the same contacts.

Yes. In the room with five lights on the one circuit, try replacing one of the lights with a small (say 20W) incandescent light globe. I think you'll find that the other four globes will then work perfectly.

[ol' boy]

I wonder if there is an electrician who knows enough to troubleshoot this... they might say normal globes work, power turns on.. no problem I dont mean to say electricians are dumb

You've just had 2 Electricians give you answers

And why didn't you tell us from the start there was no Neutral at the switch.
I'll bet that is your answer right there.

[ol' boy]

hi,


adding resistors to a mains switch

cheers

wtf?

[shonkster]

I come to this forum to get a bit more technical help so I can try to understand what's going on cause I know there are plenty of smart people on here that I can learn from.... I cant be sure that a random electrician that I ring up from the yellowpages is going to always have the technical knowledge to troubleshoot something out of the norm.... I only bought the house a few months ago, if there is something wrong with the wiring in the house then I may be able to claim it on title insurance... A few theories being given to me here has been very helpful.. ie floating ground, capacitive cabling, unbalanced circuits etc... The previous owner told me her brother or brother inlaw was an electrician so there was a lot of electricial work probably done at mates/family rates. I cant really be sure something dodgey hasnt be done
I will try putting a standard incandescent globe on the same switch that has 4 of the new globes and see what happens... thats how I tested these new globes before I bought heaps of them... if this works this is telling me the new globes are to resistive and creating a bit of residual voltage/current in the cable?
Getting the resistance tested between neutral and earth/ground may be the next step after this?
Thanks

[ol' boy]

With out all the posting and rambling on.

Get a few things straight before you run in every direction, like you currently are.

1. Get a GOOD Digital Voltage Meter, like Fluke or similar
2. Go to the "3 plate" connection at the first light fitting (as you have told us there is No Neutral at Switch)
3. Test between Neutral and the Switch wire (most likely its white)
Measure the voltage with the switch on and off (WITH THE LIGHTS DISCONNECTED FROM CIRCUIT)

Post your findings

Warning: Obviously you realise you are NOT meant to be conducting this work yourself, unless you are a licensed Electrician.
So to make a statement like the previous owner's brother was a Sparky and mates rates, etc is just hilarious, considering what you are doing!.

If you want to the problem fixed and sorted out, ring an Electrical Contractor!

[shonkster]

Point taken Its on my head... Only taking measurements at this stage... wont be going further with it

[tristen]

Down-lights, including the LED variety, have been around for some years now, so I would be very surprised indeed if most, if not all, currently licensed, practising electricians, who are engaged in house and commercial premises wiring and installation, do not know how LED downlights work and what problems are commonly experienced with both their installation and operation.

I have seen many attempts to offer help in these forums (Austech), which fall into the category of the blind leading the blind, so you are exposed to an element of risk of inaccurate advice being tendered here.
The advantage of seeking advice here is that it will cost you nothing and you are at least able to look at the track record of the advisor.

The advice offered by both freakee1 and oceanboy seems sound enough to me so I suggest that you take it.

Contact a local electrical contractor!

Attempting to trouble-shoot the problem yourself, with an obviously inadequate background knowledge, only serves to complicate matters, both for you and everybody else.

[ol' boy]

I think the username says it all

The obvious thing to be looking for here, is the induced voltage in the twin active cable (if it indeed is wired like that), when the switch is in the off position.
Hence my comment about the "No Neutral" at the switch.

[Onefella]

<from a retired electrician now in IT and electronics>

I think post #4 from member koshari is right on the money. Capacitive coupling.

It has been discussed before, and I seem to remember the solution being, to use a high-ohm resistor at the light fitting to pull the switched wire (usually white) low when the wall switch is off. This resistor would be placed between the switch wire and neutral.

The resistor has to be high enough resistance to have negligible current flow when the switch-wire is active, but enough to 'sink' the small voltage that is present when the switch is off.

Member shred's advice from post #8 would have the same effect.

btw, it is extremely rare to find a light or fan switch with a neutral wire. I have a neutral and earth in my lounge switch bank, but I did that deliberately so controls and timers could be added. Otherwise, it's pretty much unheard-of.

[ol' boy]

btw, it is extremely rare to find a light or fan switch with a neutral wire. I have a neutral and earth in my lounge switch bank, but I did that deliberately so controls and timers could be added. Otherwise, it's pretty much unheard-of.

What planet you been living on Onefella?

Every house i have wired for the passed 28 years has had Active Looping (hence N+E) at the wall switches.
In fact, Active looping at the lighting points is banned in New Zealand (from what i remember)

On top of that, 90% of houses i work in also have active looping at light switches

Active looping at the light is a cheap and nasty way to do things

Sure, it might happen when space down the wall is tight, or its a place full of arc switches (who uses those in the last 20 years?)
The only other people i have seen do it, is the cheapest or cheap House and Land Package home, where they literally want to save $100.

[shonkster]

Maybe I should change my login name.. gives bad first impressions a bit of a story behind that name not supposed to imply I am shonky (Wont go into that here) I try not to be anyway... I am just trying to understand what could be going on so I am greatful for peoples comments.

[ol' boy]

Well, the possible solution and areas you should test have been mentioned multiple times now.

What you need to understand, is the process of elimination.
And separate the House Wiring from the Introduced lamps (as obviously things worked fine before they were introduced)

Deal with your house wiring in its own right, test it with all this introduced LED lighting junk disconnected.
That is your starting point.

Secondly, you could post what LED lamps you are talking about here, so people can see what it is.

Once you have above info, you are ready to conclude your next step.

[Rocket]

koshari and Onefella are spot on the money!!