18 replies to this topic

[Snake]

Here you go:
Custom LED Sign
Do you like my user name?

[Jogumpie]

I didn't really get why you decided to use 'resistors' in some cases instead of all cases. And why not just go with regular resistors?

[Snake]

^Because I didn't have any regular resistors.

[Jogumpie]

Do you know that these are about the cheapest electronic elements?

[RCT2123]

They're basically giving them away, haha.

[Snake]

Do you know that these are about the cheapest electronic elements?

They're basically giving them away, haha.

Not where I live. There is an oil boom in my state of North Dakota and my town is in the heart of it all. Our local radio shack wants 99 cents for 5 1/8 watt resistors! I would order online but I was in a time crunch so leds were the way to go. My leds were .6 cents each so each resistor was about 10x cheaper.

[Jogumpie]

That's a ridiculous price. Still, seeing that you have like 16 parallel series of LEDs, you'd need only 16 resistors. You should be able to buy sets of 100s of resistors for, I am guessing, $10-20. Now that you aren't using qualified resistors, I am worried about the lifecycle of your sign. From what I read, you have series of 7 LEDs without a resistor and series of less (5 or 6?) LEDs with a self-fabricated resistor of which you obviously do not know the value. Resistors are there to limit the current through all these LEDs and without them (or with an incorrect value), you are risking blowing up your LEDs and worse.

[TheSUCKCrew]

Lol, I got myself 1000x resistors for 2$ a while back:D

[Maxlaam]

Not to mention that buying the proper resistors may actually tune down the brightness. It's a bit of experimenting at first to see what suits best but it's worth it. I had that problem with XenoX's blue led's, I also trimmed the voltage a little on my power supply.

[Snake]

From what I read, you have series of 7 LEDs without a resistor and series of less (5 or 6?) LEDs with a self-fabricated resistor of which you obviously do not know the value. Resistors are there to limit the current through all these LEDs and without them (or with an incorrect value), you are risking blowing up your LEDs and worse.

How don't I know the value? I its just 7 leds like the rest. And how would I blow my leds? They draw only the current that they need.

[Maxlaam]

And how would I blow my leds?

Easier than you might think actually. Using the proper resistors sure aids in reducing the chances of burning them out.

They draw only the current that they need.

Nope. The current rating in the data sheet specifies a maximum/recommended current, any more and you will damage your leds. Too little and it won't turn on. That's why you limit the current; not too much, not too little.
A led draws the voltage it needs, which is specified as the forward voltage, too much and it will go poof, too little and it will not turn on at all. It's a pretty balancing act when done exactly right.

Looking at just your resistors, I find the thread title to be slightly misleading...

[Edit]: I spotted another major flaw, taping a LED to the back to balance the brightness is NOT to be called a resistor! You still aren't limiting your current that way! Look at the forumla: R=U/I. Your U should stay the same, but your I is fluctuating because you didn't limit your current, so what happens to the R? It fluctuates too!

[Jogumpie]

Example of a LED circuit with multiple series of LEDs.

[Jogumpie]

So this could very well happen to LED circuits that don't include resistors:

[Maxlaam]

Boy oh boy, those plastic pieces hurt so much! Yeah I've had that happen once, shorted out a wire by accident, thank god I wear glasses!

[Snake]

Easier than you might think actually. Using the proper resistors sure aids in reducing the chances of burning them out.



Nope. The current rating in the data sheet specifies a maximum/recommended current, any more and you will damage your leds. Too little and it won't turn on. That's why you limit the current; not too much, not too little.
A led draws the voltage it needs, which is specified as the forward voltage, too much and it will go poof, too little and it will not turn on at all. It's a pretty balancing act when done exactly right.

Looking at just your resistors, I find the thread title to be slightly misleading...

[Edit]: I spotted another major flaw, taping a LED to the back to balance the brightness is NOT to be called a resistor! You still aren't limiting your current that way! Look at the forumla: R=U/I. Your U should stay the same, but your I is fluctuating because you didn't limit your current, so what happens to the R? It fluctuates too!

I know. I didn't have time to get the resistors because I was entering it in the make it real challange. The instructables staff loved it. It is now featured and on the homepage. I now have 1 year and 3 months of pro because this. I think I have a pretty good chance of winning.

[TheSUCKCrew]

I know. I didn't have time to get the resistors because I was entering it in the make it real challange. The instructables staff loved it. It is now featured and on the homepage. I now have 1 year and 3 months of pro because this. I think I have a pretty good chance of winning.

I wouldn't be too proud of a tutorial that may lead to blown up leds and physical injuries.

[Maxlaam]

I wouldn't be too proud of a tutorial that may lead to blown up leds and physical injuries.

This... My god their staff is retarded ...

[LaMbChOpZ]

Truthfully, this tutorial needs a complete make-over. It's not safe in it's current state (also stated by other members). I really suggest you add the resistors, redo/edit the tutorial, and make sure no one risks blowing an LED up and hurting themselves. Listen to Gump and Max; they seriously know what they're talking about (even about the staff on Instructables).

Not to put down your tutorial, but it's has a lot of spots that need a bit of fixing and tweaking.

[Maxlaam]

While it's rare for such things to happen, it surely would make it look a whole lot more professional. Right now it seems a bit like: "It works, so it's fine". But in the end it's not.

The thing that bothers me is that it's a public tutorial that will get your LED's to light up, but not in the proper way. If you want people to learn anything from it, then show them the correct way to hooking up LED's.