Smart Switch Issue - Outside 12v Lights

[CSutton]

Hi all,

Last summer I re-did my decking and installed new outside garden lights using 2 existing garden circuits the builders had previously installed. They installed the switch for these lights in my lounge (1 live, 2 switched only using 3 core cable).

The new lights are Techmar 12V LEDs

Up until this week, I’ve been using a Lightwave dimmer smart switch to control the lights and all has worked perfectly (no neutral required) … until they released their latest firmware which now causes the primary dimmer lights to flash when off! I’ve tried every setting but to no avail.

Lightwave don’t support 12v transformers and seems I’ve been lucky until now although they did send a replacement unit to double check it wasn’t a faulty dimmer but to no avail.

So I have a bit of a problem. There is no way I can pull off a neutral from outside. The wiring box is under the decking with no immediate access.

Is there a switch/dimmer I could use and anyone can recommend which doesn’t require a neutral or would it be viable (not sure if physically possible at this stage) for me to pull off the neutral cable from the ceiling rose connected to my living room light and then pass down behind the dot dab plasterboard to the garden light switch?

Any help appreciated.

Chris

 

[bernardgreen]

until they released their latest firmware which now causes the primary dimmer lights to flash

Could you ( maybe with help from Lightwave ) re-install the original software ?

 

[CSutton]

Potentially though they are not keen to support as switch is being used with a transformer.

 

[ericmark]

This device may help

it provides a leakage path for the small leakage current from switch, it fits across the supply to the electronic transformer, clearly needs an enclosure, but should work.

 

[ericmark]

Potentially though they are not keen to support as switch is being used with a transformer.

Since any LED lamp uses around 3 volt on the chip they are need to transform the supply to a usable voltage or current, there are many ways to do this, but the pulse width modulation or switch mode power supply is a common method, and should not matter if in the bulb or in the lamp or separate unit.

Using a toroidal transformer would be a problem due to in-rush but the electronic transformer if designed for dimming should work OK.

 

[CSutton]

This device may help

it provides a leakage path for the small leakage current from switch, it fits across the supply to the electronic transformer, clearly needs an enclosure, but should work.

Looks good. Could I install it above my pattress box in the wall cavity?

 

[ericmark]

I just about got one to fit in my chandelier in wife's bedroom, it was a tight fit, I use Energenie smart switches and it did stop the flashing when off, however there was also a shimmer when switched on, so swapped bulbs, and likely with the larger physical bulb would not have needed the load capacitor.

 

[CSutton]

Thanks - don’t forget I can’t get to the transformer as under decking so will need to be located at the switch.

 

[bernardgreen]

Does that device have a series resistor built in ? A fusible resistor in the device provides protection if the capacitor goes short cicuit.

Contact suppressors have a resistor built in and are ideal for this application.

KEMET RC Capacitor 470nF 100Ω Tolerance ±20% RS Components Stock Number 172-6734

Other sources are availane

 

[JohnW2]

This device may help...

4μF is far more that would usually be needed and, as bernard has pointed out, it would be desirable for it to have a series resistor (but the device you have linked to is just a capacitor).

Kind Regards, John
Edit: missing symbol inserted

 

[winston1]

4F is far more that would usually be needed and, as bernard has pointed out, it would be desirable for it to have a series resistor (but the device you have linked to is just a capacitor).

Kind Regards, John

It is actually 4µF. But still more than required.

 

[JohnW2]

It is actually 4µF. But still more than required.

It is, and I had gone through the motions of inserting the "μ" symbol - which for some reason didn't appear. Now corrected - and, as we've both said, far more than is required.

 

[ericmark]

Industrially 4 to 20 mA is a standard, many devices allow first 4 mA to work the device, and next 16 mA is used as a signal. This is at 24 volt, so not quite the same, but there seems to be no standard amount agreed on for working lamps when there is no neutral, however some power has to be leaked away even with standard on/off switch as there is some leakage on the switch wire, but it could be 5 x 2.6 watt G9 to a single G9 or 8 x 6 watt E14 bulbs, so working out a standard drain inside the bulb is not easy.

The formula

where x = resistance, f = frequency and C = capacitance was drummed into us when doing the RAE, however it is not only the switch using power, but also the cable, although Wikipedia does give loads of formula's there are just too many unknowns.

Also reaction with other components, which can cause a shimmer when switched on.

 

[JohnW2]

Industrially 4 to 20 mA is a standard, many devices allow first 4 mA to work the device, and next 16 mA is used as a signal. ....

What are you talking about? What 'device' and what 'signal'?

This is at 24 volt, so not quite the same, but there seems to be no standard amount agreed on for working lamps when there is no neutral, however some power has to be leaked away even with standard on/off switch as there is some leakage on the switch wire, but it could be 5 x 2.6 watt G9 to a single G9 or 8 x 6 watt E14 bulbs, so working out a standard drain inside the bulb is not easy.

Again, what is this about, and what is its relevance to the present discussion?

The formula View attachment 248843 where x = resistance, f = frequency and C = capacitance ....

There is no "x" in the formula, nor anything to do with resistance. Xc is the capacitive reactance.

... was drummed into us when doing the RAE ...

I'm glad to hear that, since it was then, and still is now, the correct formula for capacitive reactance

... however it is not only the switch using power, but also the cable, although Wikipedia does give loads of formula's there are just too many unknowns. .... Also reaction with other components, which can cause a shimmer when switched on.

Again, I don't really know what you are talking about in the context of this discussion.

Kind Regards, John

 

[ericmark]

We have a range of 4 - 20 mA devices we use to measure when using PLC control, the first 4 mA is ignored by the PLC and is used to power the device which allows use of two wires instead of three.

With lighting and no neutral we are doing some thing similar, every bulb has a resistor or other device to allow a small amount of current to flow, it needs it anyway mainly due to the way we drop cables to the switch, two wires in a cable will have some capacitive linking, and with two way lighting we can have maybe 10 meters of cable, this was not a problem with tungsten, but it is with LED, so each bulb has some leakage device built it.

However the big difference is there is no standard, nothing says a bulb must sink 0.1 mA or any other figure, the packet had to say if not dim-able before we left EU, but it did not have to say how much it leaks, and with a dimming switch using a neutral the leak resistor can be very small.

So you can get two bulbs which are very different in how they can handle small stray currents, and also how they react with other devices on the circuit, the large bulb has a reasonable large leakage resistor, and also after the rectifier a large smoothing capacitor, so it can deal with both the leakage and any problem forming a tuned circuit so does not flicker either. The small bulb is nearly the size of the smoothing capacitor inside the large bulb, and also has a smaller leakage resistor.

With a simple on/off switch either bulb will work, with an electronic switch it needs the larger bulb, which in this country does not comply with the law, as not got the lumen or wattage marked on the bulb.

But more to the point non of the bulbs have anything to say how much power is leaked.

I must admit I don't totally understand what causes or cures the problem, I know with 5 bulbs, swapping just one of the 5 can stop both flashing when off, that bit I can understand, but also the flicker when on, that bit I don't understand, why fitting one of the large LED bulbs stops the other 4 from flicking I don't know, only that it does, I would assume it has stopped it forming a tuned circuit? But if the flicker is caused by it forming a tuned circuit then likely we are also making a transmitter? So it may affect other items in the home?

I like LED lamps, as I am by nature a lazy man, and with old tungsten every other week I was renewing a bulb some where in the house, and I kept a supply of bulbs that is not really required now, but due to matching bulbs it is still increasing in size, the G9 bulb was a real problem the cover to left was intended to go over the quartz bulb to stop harmful rays, and to retain white hot parts if the bulb explodes, the small LED will fit inside the cover so whole chandelier looks the same with quartz or LED, but the larger bulb changes the whole look of the chandelier. I know this bulb

works, but finding them again even when I can google 22019274 G9-69SMD is not easy, I get hits saying Asda so it seems likely at one point sold in Asda, but I had to use internet, which means delay which means need to hold a stock, can't buy one so I have 4 spares and LED bulbs last years. I had one fluorescent tube replacement with LED which failed, but that was old house without SPD fitted. And some 0.5 watt MR16 LED's g5.3 12 volt from Pound World, toys really, and one G9 which I took apart to see how it worked and found a dry joint and fixed it.

I don't keep a spare dishwasher in stock, and looking at same life span, so really should not keep a stock of bulbs, but I can go out most days and buy a new dishwasher, five days without is likely the most if it failed at Christmas, but the bulbs took weeks to arrive and not found local supplier and now I have spares I have stopped looking.

With larger bulbs often one can buy smart bulbs, which at first went against the grain, as you a dumping all the control gear when it fails, but with all the problems I have had with smart switches with no neutral, I am now leaning towards smart bulbs, the main against is the time it takes to boot up Smartlife app to control them. However default is on, where with smart switch default is off, so switch the light off and on at wall and it works with smart bulbs.