Hardwiring LED's

There's NOTHING wrong with the resistor's placement in second image. It doesn't matter where it is, as long as it drops the remaining voltage (at a given current). It can even be placed between two consecutive LEDs.

I assumed that ALL LEDs are same, rated at 3 volts and 20 mA. That way, you can put groups in parallel with only one resistor (the current through the resistor will increase, decreasing its value and increasing the dissipated power).

Alex

My mistake, I was thinking backwards.

As for the parallel, I don't do that because I bought some 4000mcd red LEDs once and didn't have enough so I bought a few more and they ended up being 5000mcd and a different mA, can't quite remember what though.  Anyway, I was working with them and got them mixed up.  They are all red and I was not able to tell the difference, not really on the brightness either so having them in parallel might not be the best decision.  Although they were the same voltage and I ended up averaging the mA rating for the resistorsand they worked fine.

http://www.home.agilent.com/cgi-bin/pub/agilent/expandedresults/cp_ExpandedResults.jsp?NAV_ID=-25324.0.03&LANGUAGE_CODE=eng&contentType=Editorial&entityType=ED30&COUNTRY_CODE=US

If the link works, it's all you've wanted to know about LEDs.. poke around on the site for more info..

Jim

Wow, that website is great. Everyone should check it for a HUGE amount of info :)

Chris, no problem. As long as the current isn't TOO different, you're fine. If it's higher, than your LEDs will be brighter, if it's lower, they will be dimmer. It's just that a LED can't drop too much voltage (because its equivalent internal resistance is VERY small, so if you increase the voltage a little, like 2 volts, the current goes higher exponentially).

-Alex

LOL, yea, I'm 100% with you here, jeepmansro.

The inconvenience with neons is that they break easily, not as long-lasting (as far as I know) and consume much more current (need a bigger alternator). LEDs can be ran over with a truck several times and nothing will happen to them. They last longer and are very little consumers. The problem with LEDs though is that the light is concentrated (focused) and not as diffused (going in all directions) as neons. But that's not a problem, right???