resistor question

[roughwater71]

if i have a 7.4 li ion power source, and im running the 2v 20ma red accent led off the petit cruton sound module, with the 2 accent led pads that have a fv of 3.3v, do i still need to resist the accent led's? and if i do, do i calulate it for the 7.4v main power source, or the led pad fv of 3.3v??? also if i'm gonna run the rebel star led(blue fv unknown)off the petit cruton, do i need to resist that as well??? i'm not electronicaly incliend, just starting out, and i need all the help i can get, i dont want to mess up. a quick story for you. my father when he was younger then me, appllied to PSE&G (public service electric and gas). his last test was to build some sort of electricial box and he has only 1 hour to do it, with about 20 other students in the class. the tester said go and every one started building there box. my father was the only one that past the test. the reason why, "he was the only one that read the instructions and asked questions". thank you every one for all your help!!!

[TuxedoCartman]

The answers you are looking for are in the Petit Crouton manual. Page 10 for accent LED's, page 14 for the main LED. Short answer for your second question: the PC serves as a resistor for the main LED. You set the current for the main LED in the text files on the micro-SD card.

[roughwater71]

i gotcha! so the answer is yes, i do need to resist the accent led's. thanks, just making sure. i dont want to install them and have them burn out and possibly burn something else out. better to be safe then sorry!!! but i still dont know if i go buy the FV of the main power supply, or the FV of the accent led pads, it does'nt say that on the pc manual??? the reason i asked this is because if the FV of the accent led pads are 3.3v and the led's are 2v it is under the forwarding volts! like i said, i'm not electronicaly head strong!!! lol

[TuxedoCartman]

You're not reading what's being put in front of you. From page 10 of the Petit Crouton manual...

Calculating resistors for LEDs
R = (Vsupply – Vled) / LedCurrent
In our case, Vsupply is the voltage the board provides to power the accent LEDs, ie 3.3V. The Vled is the forward voltage of the LED, usually referred as Vf in the datasheet. The led current has to be decided by the user, depending on the brightness and the maximum rating of the used LED. 5 to15 mA are fairly common for most accent LEDs.
As an example, let’s consider a 1.6 volt LED (red) at 10 mA R = (3.3 – 1.6) / 0.01 = 170 ohm ( 150 ohm in the classic E12 resistor series)

Yes, 2v is less than 3.3v, so you do need a resistor. Otherwise, the 3.3v will blow your 2v LED.

Your problem isn't that you're not electronically smart, it's that you're not taking the time to really read what's out there, and try to understand it. The manual for the Petit Crouton alone lays out all the information you need for wiring a very nice saber (though I'll admit it is a bit vague on info regarding the 10w LED Engin's uses and wiring R.I.C.E.). You don't need a degree in electrical engineering to design a saber with that manual in your hands; all you need to do is know how to solder properly... IF you'll take the time to read it.

My advice? It sounds like you're designing a pretty run-of-the-mill PC-driven saber. If you poke around on the forums, you'll see lots of us have submitted wiring schematics for the more experienced veterans to double check. Search though my early posts, and you'll find one I submitted that I can guarantee works properly, and even has a few accent LED pointers by some very respected builders here. Perhaps you should find one such submission, and just copy what they did. I don't think anyone will cry "Plagiarism!" or "Intellectual copyright infringement!" if you do. Then if you can't figure out why they did something a particular way (such as why I had one accent LED coming off a different pad than the others), then just ask the person who submitted the plans why they did what they did.

Just my 2 Republic credits worth.

[Kevin Starwaster]

Your problem isn't that you're not electronically smart, it's that you're not taking the time to really read what's out there, and try to understand it. The manual for the Petit Crouton alone lays out all the information you need for wiring a very nice saber (though I'll admit it is a bit vague on info regarding the 10w LED Engin's uses and wiring R.I.C.E.). You don't need a degree in electrical engineering to design a saber with that manual in your hands; all you need to do is know how to solder properly... IF you'll take the time to read it.

Just my 2 Republic credits worth.

For RICE wiring:
http://www.plecterlabs.com/Media/Doc...on_R.I.C.E.pdf
http://www.thecustomsabershop.com/35...le-1-P658.aspx

Refer to the first link for which PC pads are TXD, RXD and GND and then check the second link for the RICE port for same. (both links are from the store, one for the RICE software and one for the port) People here tell you not to do through hole soldering on the PC but it's really important for those pads because they are on the bottom right under the processor itself so you really don't want to stick anything through those holes. (and they're so tiny, omg what a PITA)

As for your 2 republic credits, republic credits are no good out here, we need something more real! And mind tricks won't work on us!

[TuxedoCartman]

Haha... thanks Starwaster. I didn't actually *need* the info on how to wire up the R.I.C.E. port (managed to wire one up on my first saber, and so glad I did! R.I.C.E. rocks!) I was just qualifying my earlier statement that the Petit Crouton manual had absolutely everything you need to know how to wire up a top-quality saber. Still, thanks for jumping in with the help! (God, I love the people on this board...)

But there ya go! With the PC manual, the links provided by Kevin above, and this one on wiring the LED Engin, you have EVERYTHING you need for constructing an incredible competition-worthy saber. Unless your saber is going to incorporate some truly unorthodox design features, like multiple speakers or EL wire accents in the hilt, I PROMISE you the info you need will be in one of those three places. I will stake vital parts of my anatomy on it.

Now, Starwaster... if credits are no good, perhaps I could interest you in a wager? If I win, I get your Crystal Focus. If you win, you can keep this annoying 9-year-old boy who can't act. Deal?

[Darth Xusia]

It all depends on what the current draw of your load is. If you know that, the current times the resistance value would give you the voltage drop across the resistor. It's a very inefficient way to run your three volt circuit off though. In case one, you're dumping two times the power into your resistor and in case 2, the same power that your actual load circuit is using. Buy two D, C, AA or AAA cells and use them in series to get 3 volts.

? ? ? ? ?
You should spend some time reading the Petit Crouton manual. Using two D, C, AA or AAA cells will not get you very far.

What's with the SPAM link in your sig?

[Silver Serpent]

The spammers are getting smarter and adding in gibberish based on keywords in the posts. Single post count, recent join date, and spammer links in signatures are a dead giveaway.

[TuxedoCartman]

I don't know what you're cheap viagra from Canada talking about! That's as crazy as all the hot single girls in your area!

Seriously though, wow... they're doing a frighteningly good job. I didn't even realize that was a spam post till you pointed it out, SS.

[Jedi-Loreen]

Please don't respond to SPAM posts.

What SS said is correct.

Thanks