What kind of leds should I use for this project?

[CacheHarbor]

Hi,

I've read the forums for a while and appreciate all the helpful people posting!

I would like suggestions on LEDs to use for building a custom vehicle lightbar (fire - red/white). I have the knowledge as far as circuits and microcontrollers, but have no experience choosing LEDs.

The problem is all the LEDs I find are either real cheap, or real expensive. Does anyone have any suggestions for mid-range, say a couple dollars per LED? I guess I want the most light output for the money, I want it to appear real bright but at the same time not put $100 worth of leds in one square inch. I would really like to use RGB leds so I could alternate the colors, but from what I've found these aren't as nearly as bright as just using multiple single color LEDs, correct?

Thanks for any help,
James

 

[frenzee]

Is this for an emergency/police vehicle? I'm sure you already know that blue/green/red lights on a passenger vehicle or truck are illegal here in the states.

But to answer one of your questions, yes, RGB LEDs can be, but typically are not as bright as discrete colored LEDs only becasue they don't use the brightest available bins for building them.

 

[CacheHarbor]

I am a volunteer firefighter so I have permission, though I am really making this more as a learning experience.

Do you or anyone have suggestions of a specific led / store to buy from?

Thanks again

 

[Gunner12]

If you want to stay cheap, Dealextreme and Kaidomain has Red, Blue and Green Cree LEDs for sale. The Seoul and Cree LEDs are the brighter ones out right now. They will at least hit 80 lumen if driven at 350 mA(And at least 175 at 1 amp, up to 230 with a Cree XR-E Q5). Shipping might take a while.

Dealextreme:
Blue Cree
Red Cree
Green Cree
RGB LED
Seoul P4 U bin(Bare emitter)
Edison Opto KLC8
Cree XR-E P4 bin
Cree XR-E Q2 bin
Cree XR-E Q5 bin

Kaidomain:
Red Cree(Smaller board, bare emitter)
Blue Cree(Smaller board, bare emitter)
Edison Opto KLC8(5 pack)
Cree XR-E P3/P4 smaller board(5 pack)
Cree XR-E P3/P4 Star(5 pack)
Cree XR-E P3/P4 mini board
Cree XR-E P4 bare emitter
Cree XR-E Q2 star
Cree XR-E Q5 Star

Bin codes here

:welcome:

 

[CacheHarbor]

Awesome! I think I'm going to go with the RGB, does anyone know if the white color quality decent when driving all 3?

 

[2xTrinity]

Awesome! I think I'm going to go with the RGB, does anyone know if the white color quality decent when driving all 3?

I personally wouldn't go for RGB. White balance is pretty difficult to reliably achieve with RGB -- youll have to tweak the currents going to each component carefully to make the overall balance look "white". Also, the RGB emitters for sale on DX are common cathode, meaning it won't be possible to connect multiple LEDs in series.

For a vehicle, your best bet is to group LEDs into "strings" whose total voltage is close to 12V (5 reds in a string, 3 whites in a string), then add an appropriate series resistor to limit the current (keep in voltage straight off the alternator will be >13V). Once that's done, you can use relays and a timing chip to switch between white, and red as desired.

here is a group buy for Q5s, cheaper than DX and should arrive quicker