LED Lights flickering

[hounslowluddite]

Hi all

I have bought some of dimmable LED bulbs for two wall lights made by a company called TCP. Each light has two bulbs. They work fine if I fit one bulb, but flicker rapidly if I fit a second bulb in either light, unless they are turned right up or right down. Each light is connected to a single switch on a twin dimmer unit on the wall. The second dimmer operates a ceiling light. The bulbs are marked E14 SES 5W 330lm, LDMG 5W E14 COA 3000K 220 – 240 v 50/60hz 24mA.

I’m a complete electrical ‘numpty’, my limit is just about wiring a plug but I do have a youngster in the household who is recently qualified as an electrician. He grudgingly looked at the problem but has failed to offer a solution. However, I can see from previous threads that things like this have been discussed before and that there does appear to be explanations. However, I’d admit I didn’t understand the question or answers as it was way ‘over my head’.

Are there any numpty level explanations available for the likes of me, as to what’s wrong/ what can be bought to correct the problem? Perhaps something that I can put in front of the previously mentioned youngster, if he can be distracted from his girlfriend and killing robots or aliens or whatever, in order that he can be persuaded that it is fixable. Failing that, something that I can take down to a local electrical dealership in order that I can say “Give me one of them, please” and I’ll turn off the power and pray. On second thoughts, that’s more appealing than disturbing the youngster.

Thanks for your thoughts and contributions.

 

[Taylortwocities]

It sounds like the dimmer is not compatable with the lights. You will probably need 'low load' dimmers thaty are designed for dimming LED loads.

Something like this

 

[ericmark]

Compare it to people talking to each other no good if one can only speak Welsh and the other can only speak English. However many Welsh speakers can also understand English but not good enough to answer in English.

In the same way we have leading, lagging and resistive dimmer switches which may also have a minimum and maximum power ability, and we have a host of ways of driving LED's some which will understand the instructions from all dimmers and some which are limited to just understanding the instructions from some.

So if it says "Araf" does that mean slow, stop or care required? We see it written on the road and we know something must be ahead but not what as I don't read Welsh. So I slow down which is just as well as it means "Slow".

So back to your bulbs, if you have a Philips dimmer switch and Philips bulbs then likely they will work A1. But when you mix and match then it's pot luck as to if they work.

An LED bulb contains some electronic gizmo's to turn constant voltage into constant current and in doing that it can cause the wave form of the supply to be warped a little, if too much this warping can be seen by another bulb as instructions to dim. When on full the bulbs will not warp the supply much but once set to dim they may.

So which is easiest to swap? Likely the bulb? Which is most likely to cure problem? Likely swapping the dimmer? So if you have some where else where you also want to use LED bulbs then try another make of bulb and use the originals else where. If however that is the only room to use this type of bulb then use another dimmer.

It would be great if there was an easy works every time answer, but there isn't.

 

[JohnW2]

So back to your bulbs, if you have a Philips dimmer switch and Philips bulbs then likely they will work A1.

That's surely not at all certain, is it? It sounds as if the OP was previously using bulbs/lamps other than LEDs, so it's pretty likely that the existing ('old') dimmer (even if the same make as the new LEDs) will have a minimum load which is too high for LEDs.

Kind Regards, John

 

[ericmark]

So back to your bulbs, if you have a Philips dimmer switch and Philips bulbs then likely they will work A1.

That's surely not at all certain, is it? It sounds as if the OP was previously using bulbs/lamps other than LEDs, so it's pretty likely that the existing ('old') dimmer (even if the same make as the new LEDs) will have a minimum load which is too high for LEDs.

Kind Regards, John

I agree, but it seemed that the poster was unable to follow what the problem was when reading other posts. So I was attempting to explain as simply as I could about the dimmer and lamps matching.

Even with simple tungsten lamps the coiled coil of the lamp filament could cause some dimmers to cause odd effects. With an LED the drivers built in vary from simple capacitive dropper to complex PWM types, I did not think I could explain this in layman's language. The odd thing was he says one works OK and only with two bulbs there is a problem so it does not seem to be minimum power which is the problem but some electronic part of the bulbs interacting with each other and the dimmer. How would you explain this in layman's language.

And more to point how who you correct it.

Manufacturers are forced to tell you if not dimmable, but they don't have to tell you how their lamps can be dimmed so in real terms it's all rather pointless.

 

[Taylortwocities]

It is curious though that it seems to work with only one lamp in and not with two. I would have thought that (if the dimmer had a minumum load) that it wouldn't dim with only one lamp in either.

But maybe it depends on the dimmer electronics.


@Houndslowetc…….
The TCP site gives guidance on this and recommends some compatable dimmers
http://www.tcpi.eu/contact-us/frequently-asked-questions

 

[JohnW2]

It is curious though that it seems to work with only one lamp in and not with two. I would have thought that (if the dimmer had a minumum load) that it wouldn't dim with only one lamp in either. ... But maybe it depends on the dimmer electronics.

It is, indeed, very curious. It suggests to me that the problem probably is not due to the minimum load of the dimmer (a problem which, if anything, one would expect to reduce with increased load) but, rather, to some other incompatibility between the dimmer and LEDs.

Kind Regards, John

 

[hounslowluddite]

Thank you all for your contributions, especially the warping of wave form, the reference to TCP’s website and their FAQ’s and the reference to Varilight. Sorting this is beginning to appear do-able.

As it happens, I thought after posting this to DIYnot to make an enquiry via the manufacturer’s website contact form as well. They've replied and mentioned the Varilight V Pro Intelligent Programmable Dimmer switch. They say that it can be “programmed to work on either the trailing or leading edge”. Again, can anyone help me with an explanation of what the trailing / leading edge is, in order that I can understand how I might need to set it up when I buy one?

Reference the bulbs not flickering until the 2nd is fitted, my understanding is that it’s due to me originally having one incandescent bulb + an LED = sufficient load. But taking out the incandescent and replacing it by the 2nd LED = a reduction in load to a point where it messes up the functioning of the dimmer.

Thank you all once more for your assistance.

 

[JohnW2]

Reference the bulbs not flickering until the 2nd is fitted, my understanding is that it’s due to me originally having one incandescent bulb + an LED = sufficient load. But taking out the incandescent and replacing it by the 2nd LED = a reduction in load to a point where it messes up the functioning of the dimmer.

Oh, I see. I (and others) thought that you meant one LED + nothing, not one LED + one incandescent. In that case, it all makes sense, and is very probably just a case of the minimum load of your present dimmer, rather than anything 'clever' to do with waveforms etc.

Kind Regards, John

 

[Mikefromlondon]

Thank you all for your contributions, especially the warping of wave form, the reference to TCP’s website and their FAQ’s and the reference to Varilight. Sorting this is beginning to appear do-able.

As it happens, I thought after posting this to DIYnot to make an enquiry via the manufacturer’s website contact form as well. They've replied and mentioned the Varilight V Pro Intelligent Programmable Dimmer switch. They say that it can be “programmed to work on either the trailing or leading edge”. Again, can anyone help me with an explanation of what the trailing / leading edge is, in order that I can understand how I might need to set it up when I buy one?

Reference the bulbs not flickering until the 2nd is fitted, my understanding is that it’s due to me originally having one incandescent bulb + an LED = sufficient load. But taking out the incandescent and replacing it by the 2nd LED = a reduction in load to a point where it messes up the functioning of the dimmer.

Thank you all once more for your assistance.

Trailing and leading edge would apply to an AC waveform, where the rising voltage of an ac waveform starting from say zero volts and zero degrees, goes upwards in a positive direction and peaks at 230V and it has travelled 90 degrees of an AC cycle, then after peaking it starts to climb down back to zero reaching 180 degrees, that is half a cycle of an AC, that is the end of positive phase, then it starts to increase in the negative direction increasing steadily until it reaches a negative peak, -230V, the angle it has travelled so far is now 270 degrees, or 3/4 of a cycle, and then after reaching negative peak it starts to climb back up to zero volts and completing a full cycle of 360 degrees. That is your one cycle and the waveform is called a sine wave.

So once you know the AC waveform, the leading edge would be the rising part of the wave, before it reaches peak, either in positive direction or in negative direction, but after the peak the climbing down part would be the trailing edge

So leading edge on an AC wave would be the part from zero degrees to 90 degrees, and trailing part would be from 90 degrees to zero, likewise leading edge would be from 180 degrees to 270 degrees and trailing part would be from 270 degrees to 360 degrees.

( in terms of time, our mains power is cycling at 50 cycles per second or 50Herts, that means 1 cycle takes 1/50 = 0.02seconds or 20 mS, so 90 degrees is 5mS and 180 degrees is 10mS and 270 degrees is 15mS and 360 degrees is 1 complete cycle and so 20mS)

It is however different on a square wave, on a square wave you do not have degrees, a square wave rises to peak in a very very short space of time, taking nano seconds, so this rise in level is the leading edge, and when it has peaked and remains at peak for some time, then rapidly falls taking nano seconds then this is your trailing edge. (leading edge is often referred to as rise time and trailing edge as fall time)

Most old fashioned dimmer switches use angles in degrees to fire an electronic switch called a Triac that switches a bulb on at a certain time along the voltage waveform, for example it may fire at 10 degrees and the Triac will now latch on all the way from 10 degrees through to peak at 90 degrees and then as it climmbs down to zero, the Triac will drop out until it is fired again, this would effectively give you an almost full power, the dimmer is designed to do the same again in teh negative direction, it would fire the triac again at 190 degrees and the triac will latch on until it reaches 360 degrees and then drop off at around zero volts which is zero degrees or 180 degrees and 360 degrees.

Now if the dimmer is set to fire at 90 degrees, this would bring the lights on dim, because the mean energy is now only half, as the triac will switch on from 90 degrees to 180 degrees, and then stop until it reaches 270 degrees when it gets fired again for another quarter cycle, so total energy is half from positive cycle and half from negative cycle giving you overall half the mean energy level.

LED lights may use a different method for dimming, they use AC converted into DC and use pulse width control to cycle the LEDs ON & OFF rapidly without you noticing a flicker but the dimmer changes the amount of time the LED is switched On and the amount of time it is switched OFF, it may do so this several thousand times per second, so controlling the ON/OFF ratio to control brightness, or in simple terms controlling the average current.

Your LED is flickering due to incompatibility issues, you may be using a normal dimmer to run your LED lights which is not going to work well, hence why it flickers when you try to dim , because the conventional dimmer is not suitable to dim LED lights, an LED dimmer would have to have a Pulse width control output to feed the LED lights, again this can be a problem if you do not use the recommended dimmer, because different manufacturers use different voltage levels as well as PW modulation.

There are hundreds of different dimmers and drivers, so use what is recommended for your lights.

 

[Taylortwocities]

The Varilight V-Pro is the dimmer I posted previously

Something like this

 

[bernardgreen]

LED lights may use a different method for dimming, they use AC converted into DC and use pulse width control to cycle the LEDs ON & OFF rapidly without you noticing a flicker but the dimmer changes the amount of time the LED is switched On and the amount of time it is switched OFF, it may do so this several thousand times per second, so controlling the ON/OFF ratio to control brightness, or in simple terms controlling the average current.

Dimming an LED element requires control of the current through the element. Simple pulse width control doesn't work when dimming is required. The human eye will see the LED's brightness when the current is ON and will retain this brightness when the current is OFF and the LED element is dark. This effect in the human eye has one big benefit. Battery operated warning lights and other battery dependent lighting can be driven with pulses as short as 1/10 ON and 9/10 OFF with a high peak current double the normal current. The LED appears to be much brighter than normal yet current ( power ) consumption is 1/5 of that required to run the LED element at normal brightness.

A dimming effect is possible by pulse width control when the LED element produces UV light which activates a layer of phospher in the LED body to produce visible light of the desired colour. The phospher absorbs the pulsed UV energy and converts into visible light at a constant rate. The rate depends on how much energy is being absorbed. More energy absorbed means a brighter visible light can be produced. Hence this type of LED emitter ( element + phospher ) can be dimmed using pulse width control of the current through the element.

There are may different types of phospher. Some are slow response producing smoothed levels of visible light and these are used for LEDs that can be dimmed. Some are fast response and the visible light they produce is not smoothed and closely follows the UV pulses producing high brightness pulse of visible light and these are used for warning signs and torch lights.

That is a simplified explanation

 

[winston1]

Thank you all for your contributions, especially the warping of wave form, the reference to TCP’s website and their FAQ’s and the reference to Varilight. Sorting this is beginning to appear do-able.

As it happens, I thought after posting this to DIYnot to make an enquiry via the manufacturer’s website contact form as well. They've replied and mentioned the Varilight V Pro Intelligent Programmable Dimmer switch. They say that it can be “programmed to work on either the trailing or leading edge”. Again, can anyone help me with an explanation of what the trailing / leading edge is, in order that I can understand how I might need to set it up when I buy one?

Reference the bulbs not flickering until the 2nd is fitted, my understanding is that it’s due to me originally having one incandescent bulb + an LED = sufficient load. But taking out the incandescent and replacing it by the 2nd LED = a reduction in load to a point where it messes up the functioning of the dimmer.

Thank you all once more for your assistance.

Trailing and leading edge would apply to an AC waveform, where the rising voltage of an ac waveform starting from say zero volts and zero degrees, goes upwards in a positive direction and peaks at 230V and it has travelled 90 degrees of an AC cycle, then after peaking it starts to climb down back to zero reaching 180 degrees, that is half a cycle of an AC, that is the end of positive phase, then it starts to increase in the negative direction increasing steadily until it reaches a negative peak, -230V, the angle it has travelled so far is now 270 degrees, or 3/4 of a cycle, and then after reaching negative peak it starts to climb back up to zero volts and completing a full cycle of 360 degrees. That is your one cycle and the waveform is called a sine wave.

So once you know the AC waveform, the leading edge would be the rising part of the wave, before it reaches peak, either in positive direction or in negative direction, but after the peak the climbing down part would be the trailing edge

So leading edge on an AC wave would be the part from zero degrees to 90 degrees, and trailing part would be from 90 degrees to zero, likewise leading edge would be from 180 degrees to 270 degrees and trailing part would be from 270 degrees to 360 degrees.

( in terms of time, our mains power is cycling at 50 cycles per second or 50Herts, that means 1 cycle takes 1/50 = 0.02seconds or 20 mS, so 90 degrees is 5mS and 180 degrees is 10mS and 270 degrees is 15mS and 360 degrees is 1 complete cycle and so 20mS)

It is however different on a square wave, on a square wave you do not have degrees, a square wave rises to peak in a very very short space of time, taking nano seconds, so this rise in level is the leading edge, and when it has peaked and remains at peak for some time, then rapidly falls taking nano seconds then this is your trailing edge. (leading edge is often referred to as rise time and trailing edge as fall time)

Most old fashioned dimmer switches use angles in degrees to fire an electronic switch called a Triac that switches a bulb on at a certain time along the voltage waveform, for example it may fire at 10 degrees and the Triac will now latch on all the way from 10 degrees through to peak at 90 degrees and then as it climmbs down to zero, the Triac will drop out until it is fired again, this would effectively give you an almost full power, the dimmer is designed to do the same again in teh negative direction, it would fire the triac again at 190 degrees and the triac will latch on until it reaches 360 degrees and then drop off at around zero volts which is zero degrees or 180 degrees and 360 degrees.

Now if the dimmer is set to fire at 90 degrees, this would bring the lights on dim, because the mean energy is now only half, as the triac will switch on from 90 degrees to 180 degrees, and then stop until it reaches 270 degrees when it gets fired again for another quarter cycle, so total energy is half from positive cycle and half from negative cycle giving you overall half the mean energy level.

LED lights may use a different method for dimming, they use AC converted into DC and use pulse width control to cycle the LEDs ON & OFF rapidly without you noticing a flicker but the dimmer changes the amount of time the LED is switched On and the amount of time it is switched OFF, it may do so this several thousand times per second, so controlling the ON/OFF ratio to control brightness, or in simple terms controlling the average current.

Your LED is flickering due to incompatibility issues, you may be using a normal dimmer to run your LED lights which is not going to work well, hence why it flickers when you try to dim , because the conventional dimmer is not suitable to dim LED lights, an LED dimmer would have to have a Pulse width control output to feed the LED lights, again this can be a problem if you do not use the recommended dimmer, because different manufacturers use different voltage levels as well as PW modulation.

There are hundreds of different dimmers and drivers, so use what is recommended for your lights.

The peaks are around 350 volts not 230, but otherwise your explanation is OK.

 

[Taylortwocities]

The peaks are around 350 volts

Less than that, have you checked your calculator batteries?

A NOMINAL RMS voltage of 230volts AC gives a peak of 325volts.

 

[winston1]

The peaks are around 350 volts

Less than that, have you checked your calculator batteries?

A NOMINAL RMS voltage of 230volts AC gives a peak of 325volts.

My calculator is in my head and does not use batteries. The 350 was approx 240 x 1.5 less a little bit.

The so called nominal does not exist, the usual UK voltage is 240v, but we have been there before.