Hi Chaps I got a couple of these new dimmable gls led bulbs
like this
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they work ok, but when at full brightness I can still see a flicker in the light output.
they are in two fittings either side of an archway with a single dimmer running them both. This has always worked well for any other dimmable bulbs like normal old fashioned incandescents or those slightly lower power halogen replacements. Not so well for the flourescent dimmable gls bulbs because of the fluorescent current threshold problem.
Does the team think its a basic problem with led bulbs and dimmers or my particular arrangement in this case?
In which case should I have a dimmer for each fitting instead?
A friend has had his kitchen done, including lots of dimmable LED down-lighters, I know I'd find the flicker difficult to live with, the LEDs obviously react far quicker to 100 pulses per second than a filament, can you get a high frequency dimmer, I wonder?
1) It's a basic problem with retrofit LED replacements, running from conventional (filament lamp) dimmers.
LEDs are very easily dimmed using dimming controllers to drive them directly. I'm guessing you have a regular filament lamp dimmer, and then retrofit dimming LEDs which have been designed to run from a filament lamp dimmer. The LEDs don't have the thermal inertia of a filament lamp, and the power supplies in the dimming ones have no DC smoothing (which would prevent them from dimming), so you are seeing the chopped (phase control) waveform from the dimmer.
2) The load on the dimmer is lower than it's lowest working rating (often something like 40W). This usually causes the lamps to become unstable and flicker when dimmed below a certain point.
What you want are some fittings with raw LED connections which use an external LED controller. Then use a dimming LED controller. You can normally string several LEDs together in series to run off a single LED controller. The controller delivers constant current (normally 350mA or 700mA, to match the LEDs in use), and a max voltage or power rating which governs the max number of LEDs it can drive in a series loop. Dimming LED drivers work by reducing the drive current rather than chopping it (or may chop at many kHz which your eyes can't see). The control is usually via a 10k potentiometer and/or 10V dimming signal. Standard patress plates with 10k pots are available as a standard component to use with
10V dimming controllers (fluorescent lamp and LED types).
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