I have read through many RGB LED posts, but still a few questions remain.
I want to use a RGB LED, which one should I choose if I want to be able to read with white/white-orange light (wattage)? Is one LED enough?
I wanted to use a spherical table lamp like the ones from IKEA.
I assume I need to power the LED through an external power supply. Which one would you recommend, in combination with the LED recommended, that can power my Arduino + the LED simultaneously?
The LED probably dissipates some heat, is active cooling with a fan required, assuming I have a heat sink on the LED and a casing with some slits for air flow? Obviously I'd like to avoid active cooling, it is a lamp not a PC
My idea was to use resistive stips and map those to the PMW output to let the user choose the colour combination by sliding the finger on the stripes. It would be neat to have just a single touchpad and use one, two or three finger gestures for red, blue, green, do you think this is possible?
If you wanted to built the most energy efficient lamp you can think of, what other things would you take into consideration?
It would be neat to have just a single touchpad and use one, two or three finger gestures for red, blue, green, do you think this is possible?
You need a capacitance touchpad, and arduino doesn't have those yet. You might be able to find a third party Cap touchpad, but it might not work with arduino.
thanks for the link to the constant current circuit, that looks promising. I was hoping that someone could comment on the brightness of the LEDs. It is hard to see in the videos how bright they actually are.
If you think that 1 LED is not enough, I obviously would consider using a couple of them in series but as I have no idea how bright they are, I wanted to get some input before I go and buy them. At ~18GBP/LED (http://uk.rs-online.com/web/p/visible-leds/6675824/) I do not want to buy more than I need. The important thing for me is, that I want it to be a reading light too.
As a reading light I assume your pointing the light at the target (book reading area), I think it will be plenty bright enough for that. The LED I bought was only £5.50 and with the OTT heatsink still only just over a tenner. Why buy from RS when eBay will do it cheaper. If 10W is not enough then they do bigger versions.
I use 2 watts (warm white / generic emitters) in my desk lamp (no other lights -- except the TV when I'm building circuits. 1 watt is equivalent to about 10 watts of incandescent light, but LEDs are much more directional than incandescent bulbs.
A 10 watt LED would be blinding. If you look directly at a 10W LED at close range you would be seeing spots for a while.
I was now thinking that I could use a 10W RGB like you (Riva) did and a separate, lower wattage, warm-white LED for the reading light.
As I wanted to use a spherical lamp (white glass bowl), I need quite some brightness to make it bright enough for reading, but 10W seem too much. Also the power consumption on those is high as well. I will check what good old ebay has in stock for me.
As the constant current controller is PWM controllable then you can dim the level if it's to bright.
If you want an overall white light then maybe a florescent tube would be better as LED's are quite directional.
I use a white plastic cap off a spray can as a diffuser to spread the light and prevent the multi-colour shadow edges.