Hello. I would like some light bulbs for my room that are a warm orange-white when dimmed, but shift to a neutral white when pushed to full brightness.

Fortunately, there is already a product on the market like this; Philips Warm Glow. The problem that I have with these is that they are quite warm-coloured even at full brightness. The colour temperature only shifts from 2200K to 2700K. I want it to start at 1800-2300K and shift to 3500-4200K at full brightness.

I don't know how Philips achieves this, or what power LED's they use as components. Are there LED's that naturally shift colour based on current? But my idea to get this effect is to wire a set of orange-white LED's in parallel with a set of neutral white LED's (or even cool white). The orange-white LED's would be linked in series with a small resistor, and the whole series would have a lower voltage drop than the set of neutral white LED's. This way, they would turn on at a lower voltage, but have less brightness at full voltage than the neutral-white LED's.

I can get some LED bulb kits on Toolboom and change the LED's, or I can buy the LED driver and LED housings separately. Although they don't include any curcuit diagrams, I figure that the aluminium PCB's for the 5730 LED's have the LED's wired for two parallel series. The reason I think is because their LED driver has a max current output of 300mA, and the 5730 LED has a 150mA maximum rating. They all have even numbers of LED's. However, it should be possible to change the circuit if I don't connect the + & - leads in the intended places.

Does anyone see any issues with my plan, or have some advice?

 

If you are a developer -

A fairly straightforward way of doing this is using RGB LEDs, each LED driven
by a PWM.

Here is a project done over Bluetooth (BT)-

http://www.cypress.com/blog/problem-solver/project-034-rgb-led-control-over-bluetooth-low-energy

A flood done over BT -

http://www.cypress.com/blog/problem-solver/project039-ble-rgb-led-flood-light

https://www.allaboutcircuits.com/projects/rgb-led-color-blending-fun-cypress-psoc-6-ble-kit/



Regards, Dana.

 

I had an old scan from a Danish magazine, which describes some color temperature changing Tiger Zenigata LEDs from Sharp.

There is something to be found on Google, but I have not looked into it.

But from the Danish text, the damped temperature is 2000 K and at full light is 3000 K. Both values I will call Warm White.

 

Forget trying to do this in a linear electronics kind of way, based on current.
To get LED's to dim in a visibly linear way, you need a highly non-linear current function, hard to achieve with linear parts.

It's wayyyyy easier to do it digitally, using PWM to control two different circuits.
One circuit with cool white LED's and the other with warm white.

 

Forget trying to do this in a linear electronics kind of way, based on current.
To get LED's to dim in a visibly linear way, you need a highly non-linear current function, hard to achieve with linear parts.

I just realized that the products I linked to are not labeled "dimable". Here are the dimmable LED kits and dimmable LED driver. They regulate output current based on AC input from a dimmer switch.

When you say "linear", do you mean analogue? LED's are nonlinear in voltage-current relation.

If the orange-white LED's have a lower voltage drop but higher series resistance than the cool-white LED's, than shouldn't they turn on at a lower voltage/current? What issue may I have?

By the way; I already have a specific place to fit them so they will probably have to be in the form of screw-in bulbs.