leds without resistors ???

[jonnydaz53]

hi guys and gals i am still trying to find the best way to backlight my pit. i have recentley come across a guy at

http://translate.google.co.uk/transl...GB288%26sa%3DG

and he uses a 12v atx power supply which supplies 4 x 3v white 20000mcd which he wires in series without a resistor not if they are 3/5/8mm leds but he uses 160 of them ! and the pit seems nice.

I was thinking of copying his layout ...

any thoughts ???

thanks in advance

john d

[dnoize]

he doesnt have them to 12V directly but uses this regulator, which can be found on his homepage too:



Stef

[jonnydaz53]

any ideas regarding led specs?

thanks

john d

[brianwilliamson]

That is not the correct way to connect up the leds. They must be connected in Parallel.
The specs for the leds all vary . When you buy your leds look at the specs, they will tell you the maximum voltage. That is the maximum you can apply before they go POOF !! Do not worry about the current and make sure all leds are the same and you will have no trouble. Buy all you leds at once will ensure you have the same ones.
.............Brian W.

[TasKiNG]

you can connect them up in series or parallel but you must be careful not to over drive them, so ensuring that each one has the correct voltage across it / current through it is esential.
Have a look at this article, It is an excellent article on how to connect leds:-

http://www.theledlight.com/ledcircuits.html

Cheers

[brianwilliamson]

I am sorry for repeating myself, but only connect up your leds in parallel.
There is a very good reason for this, that is that if you blow one led for a start you lose the lot !!
The other reason is that you may need to connect 100 leds in your overhead for example, and the only way you can do that is the same way that you have your house wired.......in parallel.
Hope this explains things a little more clearly.
.................Brian W.

[TasKiNG]

Brian,

I agree that it is best practice to connect LEDSs in parallel for the reasons you have mentioned but it is incorrect to say that they must be connected in parallel hence why I have linked to the article that shows 3 methods of powering leds.

Cheers

[chrisdanker]

Gents,

Anyone ever considered wiring up the backlighting with the LED strips as seen in this link:

http://www.besthongkong.com/index.php?cPath=21_76

Could be an easy option to avoid unnecessary soldering work....

Regards,
Chris

[mpl330]

Chris,

I've used some LED strips for back lighting (as well as cold cathode tubes and single LED's) and they are quite good. They use 12v direct and come in strips of 12 which you can break up into 4 lots of 3 LEDs and have built in resistors - I have even managed to short a block out and it only burnt out 1 LED leaving the other 2 in the block intact ( was holding the strip in my soldering "grip" and shorted the +ve and -ve strips)
I am using the cold cathode tubes for my Ped and OH backlighting and the "Background" for the MIP, the LED strips for the backlighting of the FMC, the lower MIP swicthes & AFDS Flood and LED's for the MIP backlighting.
The LED's have been the most disappointing for me as I have some "hot spots" and they do not distribute the light so evenly - oh well version 2 may improve that

Cheers
Mike