Need help wiring a LED backlight

[OdiWan72]

Hi all

I´m working on a(nother :rolleyes) blaster currently and bought a flat LED backlight for lighting the counter.
Problem is, that I don´t have any clue about electrics...

The backlight is described to work with a current of 3,2V-3,6V
I tried a 3V battery pack and it seems to work, BUT...do I need any resistors????

In addition to that I´d like to know how to "read" the capacity of a resistor.
I know the color of the different stripes stands for a specific number, but do I start to read from where the GOLD stripe is or the opposite site :$

Any help is highly appreciated since the LED-backlight will be encased in the blaster without any chance to change it later. So I´m interested to have it last as long as possible.

Many thanks in advance, Markus

 

[Roughneckone]

This should help with the LED:-

LED Calculator

And this should help with reading the resistors:-

Resistor Color code Chart

Roughneckone

 

[BOBATAFF]

hi marcus

basically no you dont need anything else for it

i often mess about with light and sound effects for my props ( bin sowieso KD für steurungs im beruf )

the back light is just like a led + and - polls just solder a battery pack ( 2aa batterys would do the job )
and a on off switch in it and thats it mate

im working on flashing leds and sound for my protonpack and PKD at the moment

if you need any help with this just drop me a mail im not that far away from you

jay

 

[exoray]

<div class='quotetop'>QUOTE(BOBATAFF @ Jan 4 2007, 02:20 AM) [snapback]1390221[/snapback]</div>

basically no you dont need anything else for it
[/b]

This is incorrect, you always need to limit the current to LEDs. There is no exception unless you want them to fail.

LEDs, are current driven not voltage driven like bulbs... So giving a 2.5 volt LED a full unrestricted 2.5 volts will kill it, you need to limit the flow (current) with resistance...

Some LEDs and/or LED packages have built in limiting but they are few and far between, generally I see them for automotive use... Also in some rare cases (mostly with small button cells) an external limiting resistor is not needed as the battery itself has enough internal resistance and simply can't overpower the LED...

99% of LED products will plainly state a voltage@current rating, and you need to limit your supply to this value...

Simply hooking your LEDs to say 2 AA batteries "might" work for awhile, but instead of your average 100,000 hour LED life you can expect to count life in 100s of hours, possibly much shorter if you don't make LED popcorn immediatley...

So back on subject, the paperwork with the LED backlight should have included a mA rating (ie 3.2-3.6V@20mA) and you need to limit your power source to this value... The links provided will help you determine the value, always go to the next larger value resistor if you can't get the "correct" value...




And here is a resistor color band calculator, actually a bunch of electronic calculators...

The resistor one is very newbie orientated, just plug in the band colors and it tells you the value, or plug in a value and it tells you the colors, no looking it up on a chart...

http://www.electronics2000.co.uk

Click on the "Calculators" link

 

[Cptnchaos]

I would LOVE for someone to actually make a short HOW TO video with LED's. To the layman LED calculators and schematics are like greek.

Its HARD to just willy nilly guess how it works, or what wires to use or how to hook them up.

If someone is willing to make the video, I would be MORE than happy to host it on my site.


Thanks

Damian

 

[exoray]

<div class='quotetop'>QUOTE(Cptnchaos @ Jan 4 2007, 01:47 PM) [snapback]1390518[/snapback]</div>

I would LOVE for someone to actually make a short HOW TO video with LED's. To the layman LED calculators and schematics are like greek.
[/b]

Yeah, but to do it right they are needed... Or at least you need Ohm's Law...

There is not ONE solution that works, there are no real standards in regards to LEDs so from LED to LED the value of the resistor needed is unique... There is also the issue of series vs. parallel and/or a series/parallel setup... The power supply used?

All the factors are pretty much unique to each application, and change the necessary parts...

As for wire people focus too much on getting the "right" wire... Just get some Honestly for most battery LED circuits just about any wire will work... Try to stick to stuff large (lower number) then say 30 gauge as it's harder to work with when it's this thin... I would say a good generic 'works for most' common battery projects would be 24 gauge.. Stranded or solid makes no difference unless it's going to be under stress (movement)

 

[Cptnchaos]

<div class='quotetop'>QUOTE(exoray @ Jan 4 2007, 08:28 PM) [snapback]1390546[/snapback]</div>

<div class='quotetop'>QUOTE(Cptnchaos @ Jan 4 2007, 01:47 PM) [snapback]1390518[/snapback]

I would LOVE for someone to actually make a short HOW TO video with LED's. To the layman LED calculators and schematics are like greek.
[/b]

Yeah, but to do it right they are needed... Or at least you need Ohm's Law...

There is not ONE solution that works, there are no real standards in regards to LEDs so from LED to LED the value of the resistor needed is unique... There is also the issue of series vs. parallel and/or a series/parallel setup... The power supply used?

All the factors are pretty much unique to each application, and change the necessary parts...

As for wire people focus too much on getting the "right" wire... Just get some Honestly for most battery LED circuits just about any wire will work... Try to stick to stuff large (lower number) then say 30 gauge as it's harder to work with when it's this thin... I would say a good generic 'works for most' common battery projects would be 24 gauge.. Stranded or solid makes no difference unless it's going to be under stress (movement)
[/b][/quote]


I understand what you are saying, But I would like to at least see someone wire something generic up and SEE it done. Then have them say this is a simple ONE LED configuration... if you wanted to wire TWO LEDs of this type you would use the calculator and then do this...

Just a simple demonstration would be wonderful.

I am sure its more simple than I am imagining.

I appreciate your info.

D

 

[motman241]

Even in a two LED circuit, there's too many variables. With each variable comes a new recalculation of the circuit.

Physically putting a circuit together (soldering) is different than the calculating before that.

 

[WookieeGunner]

As others have already mentioned, there are way too many variables. For example just going from 1 LED to 2 LED's changes depending on wether you wire them in Series or Parallel.

Here's a handout I wrote several years ago. Feel free to email me about it:

http://www.highlandcitadel.com/sith/LightingClass.pdf