led systematic to layout

[melinda123]

I am trying to make a led light for my desk using 50 white 3mm leds.

I have a plexi 1.5inch x 36inch that i am trying to get the leds in a line to light up my entire desk. (note the 1.5inch is the width)


I just cant seem to visualize the layout. It has been 6 years since I have done electronics work so I wanted to do something simple. ha


Thank you so much.

 

[CocaCola]

Like this?

 

[melinda123]

Like this?

Thank you that was exactly what I was looking for.

I feel stupid now, Thank you.

A mod can close the topic.

 

[Wabajig]

Your idea is good except I would replace the resistor with another LED, that way there is no power loss and it puts 3V a piece on each LED. Except on the last 2 LED's, I would just add 2 more LED's. Keep it simple.

 

[(*steve*)]

Your idea is good except...

Except nothing. Your idea is very poor and demonstrates a lack of understanding of LEDs.

I agree that the last string should have the same number of LEDs as the rest.

Perhaps you should read this.

 

[Wabajig]

If your LED's are the same and were not talking about any change in supply voltage. This isn't rocket science for standard LED's, if the 4 LED's are too bright put 5 in series. Try it on 5 in series and post your results.

 

[CocaCola]

If your LED's are the same

That is a big IF...

and were not talking about any change in supply voltage

Another big IF...

And you also assume the LEDs want 3 volts, most white LEDs want a little more, doesn't mean they won't work at 3 but, again you are in the IF category...

And last but not least, YES you can skip the resistor (there are some instances that it will work) doesn't mean it's proper, just like you can skip fuses...

This isn't rocket science for standard LED's, if the 4 LED's are too bright put 5 in series. Try it on 5 in series and post your results.

4 is pushing it with white, 5 will likely leave you in the dark, using a RESISTOR to limit current to a current driven device is not rocket science either

 

[BobK]

Wabajig,

You misunderstand the use of the resistor in driving LEDs. It is to provide a negative feedback to any increase in current in the LED, which can happen, for instance, as they heat up. Essentially, it is an el-cheapo current regulator.

And LEDs (even the the same part number) will vary in the their voltage drop at a given current. Look at a datasheet, there is often a range of several hundred mV for the max and min forward voltage at the design current.

Bob

 

[CocaCola]

I feel stupid now, Thank you.

Don't feel stupid, sometimes the obvious just doesn't click right away

And trust me there are still some that will say "What?" to what I posted and want pretty photo realistic pictures of a battery, LED, resistors, and wire before it makes sense...