People hate resistors for their LEDs

CrossRoads:
Look at the pictures?

you biuld it on your "breadboard", then it makes the schematic

There's the problem then - user gives up control - or more typically has no clue - and then autocreated schematic is just crap.

yea man, he linked two sites, if you look at the picture on them its a led with no resistor, leading back to

Thoughts 2 & 3 seem not to have anything to do with resistors.

yea they do, click on the link and look at the picture, no resistors on led's

sheesh :stuck_out_tongue:

You're right, I hadn't opened the links.
Saw /download on the first one, assumed it was a lead in to download fritzing.

Hi Guys,

hope this isn't a proverbial grandma-egg-sucking moment, but you can get leds suitable for 5v use with built in resistors
UK: TruOpto OSR6LU5B64A-5V 5mm Red LED 5V 60° 150MCD Diffused | Rapid Online

I think there are 12v ones too.

I don't like fritzing either, I prefer circuit diagrams every time.

I will say that the high power LED's that are sold with the current limiting already on the heatsink are awfully nice to use, even if they are a bit more expensive. I've paid as much as two dollars a watt, but usually they end up being around half that, at a buck a watt, give or take, for whites in the 2watt range. Feed them anything from 3.2 to 6v, they self limit at 500ma or thereabout. Here's a link:

EDIT: Got diverted while getting the link, hehehe:

http://www.ebay.com/itm/10x-2-3W-LED-3-2-6V-500mA-Warm-White-for-Camping-Light-DIY-/180857225621?pt=Lamps_US&hash=item2a1bee4195

Now, I will say that it does require extra heat sinking in actual operation- but running a couple in series from 12v works great. I suppose running three ought to be fine at 12v. Its a lot of light for cheap money... The link has them at under a buck each for ten. I am not connected to it in any way other than saying I've bought them and though they seem a little dimmer than expected given the power draw, but not so much that you'd actually care much... I use an NPN transistor to switch the ground side to provide PWM.

![](http://i.ebayimg.com/t/10x-2-3W-LED-3-2-6V-500mA-Warm-White-for-Camping-Light-DIY-/00/s/ODI0WDEwMjQ=/$(KGrHqNHJEgE+eDo7sikBQW!7JTYDQ~~60_35.JPG)

They are awfully convenient to use, when you don't want to diddle around with constant current sources...

"Here's a link:" or not :wink:

There are 12V LEDs with resistors for sure, with mounting hardware even.
Pricey for experimenting, great for final installations.
Some examples
http://www.superbrightleds.com/cat/led-wired-bolts/

When doing a quick test, I like to plug one leg of a standard led into the Arduino female. I have some 560 Ohm resistors soldered onto flex jumper wires at one end, and croc-clips on the other. This is so I can clip the croc onto the other LED leg, and plug the loose end of the resistor into another female. The croc-wire-resistor makes it easier to move between components and arduino pins.

Come to think of it a croc-resistor-croc might also be useful.

I have similar - a couple of LEDs with a resistor soldered to one of the legs.

CrossRoads:
I have similar - a couple of LEDs with a resistor soldered to one of the legs.

yea I have a small handful of those

I got lazy and bought 50 "prewired for 6V red LEDs" from eBay. Like these: http://www.ebay.com/itm/50-Pre-Wired-6v-3mm-Red-LEDs-PreWired-Red-6v-LED-/160596848997?pt=LH_DefaultDomain_0&hash=item2564517165

I had a UV led on a pot and made the mistake of turning the pot too low. Weird smell.

Hardest part for me is trying to remember how to determine the resistor value, which I have to go search on to re-check even if I do think I remember just to be sure which I'm not. So I aim high as I don't like leds hurt-my-eyes bright anyway.
I run 340+ ohms at 5V with standard 5mm reds for indoor use. Maybe they'll live longer, certainly they use less power.

I used 1k for nearly all my "indicator" LEDs. With modern LEDs, that's plenty bright, and it's pretty-much always safe (<5mA) 1k resistors are useful for LOTS of things!
Now, when you get to illumination rather than indication, you can start worrying about "correct" LED resistors.

I use this a lot.

I just remember the formula
(Vs - Vf)/.02 = resistor

EVP; I bookmarked that page twice and Karma'd you once.

Crossroads, I never tried but can I get Vf using a meter on the led?

One way I can get at least close is get the led in bright light and see the V it generates.

Use 5V and 270-330-470 ohm resistor, something in that range, measure Vf across the LED.
You cannot measure it without current flowing.

just do what i do, dont use resistors, i just keep using the leds till they pop and fizzle. they're so cheap just buy tons of em. :fearful:

i just keep using the leds till they pop and fizzle

Maybe fair enough on the bench but what about in production?

The BBT episode where Sheldon was on at Penny about her check engine light being on, and he wondered if there was a check the check engine light light. (As he does....)

Imagine the liability claims if peeps' engines blew up because the oil pressure lights had all popped and fizzled themselves to death?

JimboZA:

i just keep using the leds till they pop and fizzle

Maybe fair enough on the bench but what about in production?

The BBT episode where Sheldon was on at Penny about her check engine light being on, and he wondered if there was a check the check engine light light. (As he does....)

Imagine the liability claims if peeps' engines blew up because the oil pressure lights had all popped and fizzled themselves to death?

hmmm, maybe not using resistors is why i cant get the pin 13 blink sketch to work?? :~ and if you work with the engineers you spoke of in another post, the ones who ask everyone else for answers, you can easily lay the blame with them because they're clueless already!! :astonished:

lol but im only kidding bout not using resistors

Pin 13 led has a resistor. I hope you're joking about not getting it to blink.

Feed a led low enough V and you don't need a resistor but at 5V the lifetime is amazingly short.
Back in the 90's I saw a 555 circuit that ran red leds on very short 9V pulses yet allowed a lifetime of minutes.... it said.... I never tried. The purpose of that one was to make very bright pulses for a fake laser.