New dimmer switches flickering with led downlights

[steveinoz01]

Hi

Our electrician has just fitted dimmers to 4 rooms which all have multiple new LED down lights. The dimmers are not happy working with the LED’s and are doing the following:
- flickering on full or dimmed settings
- when dimmed some Lights go off completely and others stay on
- when first turning on the lights they sometimes go dim then bright and dim again a few times without turning the dimmer.

The electrician has changed the original make/brand he choose for another one but the problems continue. Sorry, I don’t know the makes used. We need dimmers that can do 1, 2 and 3 light circuits to suit the various rooms they are being used in.

Anyone experienced this issue and found a solution?

Could it be the LED down lights that are the problem? They are apparently designed to be dimmed.

Thanks.

 

[bernardgreen]

The electrician has changed the original make/brand he choose for another one but the problems continue.

He needs to change the type (*) of dimmer for one that is compatible with the drivers in the LED lamps.

(*) leading edge or trailing edge, minimum load to be less than the minimum load the lamps present when dimmed.

We need dimmers that can do 1, 2 and 3 light circuits to suit the various rooms they are being used in.

Then you may need three different types of dimmer in order to match the various different loads on the various rooms.

That may not seem helpful but dimming LEDs really requires the lamps and dimmers to be supplied as matched pairs. Mix and (mis)matching lamps and dimmers seldom works unless the installer has the nowledge and experience to make a good match.

 

[steveinoz01]

Thanks for this info. At least I better understand what the electrician needs to be trying to do.

Having looked up the two types you mention it would appear he is using trailing-edge dimmers but they are obviously not compatible with the chosen down lights/driver. I will try and find out what brand of down light has been used to see if I can find a more compatible dimmer to try.

Thank you.

 

[Taylortwocities]

If they are ELV types, you'll need to find out what type of driver he has used.
This too needs to be compatible with the type of dimmer.

But surely, you should be having the installer resolve this, if you have paid thim/her to provide a working/acceptable solution for you?

 

[ericmark]

I would agree with Taylortwocities don't play or get involved let him sort it. Dimmers are a real pain, I have ripped out all of mine. Good quality LED lighting has drivers specially designed to give exactly the correct current through the LED what ever the supply voltage does, within reason my outside lamp will work 85 to 250 volt it says.

However to dim the lights the LED needs to use very poor current control which is voltage and likely frequency dependent, they will give far less lumens per watt and are likely not to have the output claimed on the box. However using low voltage (230 volt) it may drop from 100 lumen per watt to 75 lumen per watt but as long as dimmer is designed for use with LED lamps it should work.

Using extra low voltage however you are trying to get a 12 volt power supply designed to smooth out any voltage variations to interpret the wave form chopping as an instruction to reduce output, and today there are so many devices which distort the wave form including so horrid devices like those which try to send LAN signals over the power lines it is just asking for problems.

 

[ban-all-sheds]

However to dim the lights the LED needs to use very poor current control

Or PWM

 

[ericmark]

Or PWM

Bulbs I have seen with pulse width modulated drivers built in could not be dimmed, they did however report 100 lumen per watt and for the extra low voltage types rated 10 - 36 volt DC. With low voltage rated 85 - 250 volt AC. Most bulbs which can be dimmed use a simple capacitor to limit current (low voltage) or resistor (extra low voltage) and report only around 75 lumen per watt, in fact some of the extra low voltage are down to 25 lumen per watt. Because dimmer switches often have no neutral the bulb needs to pass a little current without lighting, as a result the larger the bulb the better lumen per watt.

Personally since a LED bulb retains same colour when dimmed it does not give the ambiance of the old tungsten bulb so I have got rid of all mine, it was an 80's thing and I have moved on.

 

[bernardgreen]

Or PWM

PWM does mot provide good dimming for LEDs,

For an LED without phospher :- While the current is flowing the LED element emits full brightness and when the current is not flowing the LED goes dark. The human eye retains the brightness of the LED when on and this persists while the LED is dark.

In LED lamps with phospher the phospher does tend to everage out the pulse of bright and dark from the LED element.

 

[ban-all-sheds]

https://www.google.co.uk/search?q=led+dimming+pwm+vs+constant+current

 

[aptsys]

PWM does mot provide good dimming for LEDs,

For an LED without phospher :- While the current is flowing the LED element emits full brightness and when the current is not flowing the LED goes dark. The human eye retains the brightness of the LED when on and this persists while the LED is dark.

In LED lamps with phospher the phospher does tend to everage out the pulse of bright and dark from the LED element.

Drivel

 

[bernardgreen]

Drivel

Is it drivel ?.

From a US patent application that was granted in February 2000

Illumination device using pulse width modulation of a LED
US 6028694 A
Abstract
An illumination device utilizing a pulse modulation technique of a solid state light source to provide increased light output for a given heat load. In a preferred embodiment, power is supplied in pulses to periodically activate a short wavelength (i.e., blue) emitting LED, which in turn stimulates a phosphor-based color conversion system to produce sustained white light. In response to a pulse of power, the LED emits an intense burst of short wavelength light. The burst of light from the LED briefly excites the phosphor system, producing a bright illumination. During the interval while power is dissipated in the LED, the LED warms. After the pulse ends and before the next pulse begins, the LED cools because no more power is dissipated in the LED. However, the phosphorescent behavior of the phosphor system causes it to continue to glow for a period of time after being excited. The intensity of the illumination produced by the phosphor gradually decays during this period. The average illumination produced by the preferred embodiment over the entire period from the beginning of one pulse to the beginning of the next is higher than a conventional LED illumination device using constant power dissipation for a given heat load.

 

[flameport]

Patents are regularly granted for all kinds of spurious, technically incorrect and totally impossible things.

The presence of a patent just means someone with money to waste applied for it, and the relevant authority decided it was different enough from existing patents that they actually bothered to examine.

Most patents are drivel.