Then they should use a driver that uses a single resistor to set the overall max current for the device, and offers software control of the brightness.
MAX7219/7221, TLC5490, WS2801, WS2803, etc.
Thoughts 2 & 3 seem not to have anything to do with resistors.
I am no engineer but I didn't like fritzing either after tinkering with it a bit. That was a year or so ago. Now I find some use for fritzing. You can draw up simple diagrams with their breadboard and post the image. With an actual breadboard and parts (who has time to build a voltage divider?!), you take a shot at it, the perspective is always screwy. With pins, headers, wires and the breadboard not at the same depth of view, the picture could easily be misleading. But with fritzing it's all good.
"You can draw up simple diagrams with their breadboard and post the image."
which we engineers don't like because the parts show up as block boxes with no clues as to what the wire is connected to.
even a simple transistor - no way to tell if connected to Emittter, Base, Collector - all the stuff that a simple schematic shows.
Post the schematic, that is so much more informative.
I have yet to see a decent schematic posted that was created in fritzing.
CrossRoads:
Thoughts 2 & 3 seem not to have anything to do with resistors.
look at the pictures
and fritzing does schematics, the idea is you biuld it on your "breadboard", then it makes the schematic, then I think it can do simple PCB stuff, but no one ever makes it that far.
CrossRoads:
Thoughts 2 & 3 seem not to have anything to do with resistors.
look at the pictures
and fritzing does schematics, the idea is you biuld it on your "breadboard", then it makes the schematic, then I think it can do simple PCB stuff, but no one ever makes it that far.
I actually use it to design and print PCBs. Had to switch from Eagle when I decided to start selling some of my projects, didn't want to drop the $80 on a license. It does have some bugs, so I usually just use the breadboard view to drop parts on, then do my own routing in the PCB view. I have never been able to make a schematic look nice, so I usually ignore that view.
Any other software recommendations? I was going to try out Eagle again, but it seems you have to actually mail them a form now (is this the 1920s?). Scratch that, found the download link.
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:
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.
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 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.