A friend would like to know how difficult it would be to mod her ikea light fixture so that the fixture’s led light strip can be dimmed. Actually I’d like to know since I’ll do the work for her.
It has to be dimmable via a wall dimmer. She doesn’t want a remote control or dimmer stuck to the side of the fixture. So what’s involved in making this happen? I assume she’ll have to buy a new LED strip? One with a driver that allows dimming? Another consideration is wavelength. The one she has now is a harsh, fluorescent colour and I think she’d be happier with a warmer colour closer to daylight.
Which specific fixture does your friend have? You can change the brightness of an LED by using PWM or by adjusting the voltage. Unless it’s an RGB LED, you can’t really adjust the colour it outputs. Perhaps some diffusing filter would help with the colour, but it’s hard to say.
Short answer: Difficult unless you get lucky and find a constant current supply that will match the current required by the LED strip (small odds) and supports dimming from the input voltage.
You should start by finding out how the strip is wired ( serial=high voltage or parallel=low voltage ) and how much current does it need. Then you can search ebay for a LED power supply that will support dimming based on the input voltage and has the right outputs to match the LED strip.
Unless you have a lot of experience with electronics I would discourage you from building one of your own as there are dangerous voltages present in those kinds of supplies and then there is the safety factor for long term use.
Since you’re willing to consider replacing the strip, it wouldn’t be difficult to change the light colour. There’s lots of dimmable LED strips out there for cheap.
I expect the tricky part would be the wall dimmer. I’ve never seen a wall dimmer that wasn’t connected to a hardwired light fixture, and I presume this IKEA fixture plugs into a wall socket. Not sure what the solution to that part of the problem might be, but I understand someone’s reluctance to use the ugly little RF remote they suggest for use with that LED strip I linked above.
Edit: I have no experience with that particular strip, I just picked the top result of a ‘warm white LED strip’ googling.
Triac-dimmable LED drivers are certainly available; the technology exists and is desirable, so there’s a fair amount of this out there for use in home lighting applications. They’re not exactly cheap, but are designed to last and with proper safety standards.
If you want to continue using the existing LEDs, you’ll need to figure out if they need constant-current or constant-voltage drive, and what the requisite current/voltage is. As a high-volume consumer product I would guess they are CC, but may have a nonstandard current requirement which would make them more difficult to drive with an off-the-shelf driver. It seems that the home lighting industry has standardized around 350mA increments (fairly typical for a 1W white LED), at least on the low end, for CC drivers, so if that’s the kind of LEDs that are in it, you might be in luck. Measure the current through the existing LEDs and if possible get a CC driver to match it.
Otherwise you’re designing something from scratch and can certainly come up with a workable solution. I’m not so sure where to get LED strip that’s just strips of 1W LEDs (most are smaller 5050 LEDs, and with integrated resistors to be driven by 12V), but I do have an example of a suitable driver:
You can probably find similar products at lighting stores locally just make sure it’s triac / phase cut dimmable and suitable for the type of LEDs you are using.
Okay, so the Godmorgon connects directly to mains power. Does anyone know if a standard wall dimmer switch would play happy with this? I haven’t found any info online about its internals.
Wall-powered LED drivers that aren’t specifically designed to work with dimmers will usually just maintain constant output until they drop out entirely.
FYI, this month BC Hydro Powersmart rebates are avl. on various LED bulbs (and fixtures?). For sure at Costco. I believe also at London Drugs, and likely at Home Depot etc. too.
This is one way, it is not the only way. I’m not sure how the commercial bricks do it; my suspicion is that they are using the phase cut as an input for the current regulator setpoint, not a separate PWM process after regulation.
If you don’t have a photodiode handy, any LED (or even some glass-packaged normal diodes) can be pressed into service as one. See: How to Use LEDs to Detect Light - Make: which should let you see the pulse pattern (if there is one that’s visible) on the output. Or a good 'ol CdS cell, though with much less bandwidth it’s probably still fast enough.
So just to be sure I understand, I could swap in a triac controlled string of LED’s that it should be possible to then dim using the wall mounted dimmer?
I think if I can get the parts for say around $80 then she’d go for it.
They come in kit form and you can add remote control or use in wall dimmers. Not the cheapest but definitely easy to put together and CSA approved etc so you not likely to kill yourself.
That actually looks like a really good option Majijc. I’ll run it by her and see what she thinks of the cost but it certainly looks like what she wants and it’s sweet that it comes as a kit. CSA approved is also a nice touch. Thanks very much for that.