Nano Biscotte, Resistors and Me.

[deckroid]

Hey there

So, I have a quick question. I recently added sound to my saber, and I am getting some odd results. I have a Rebel Deep Red LED connected to a 5W 1 Ohm resistor, a 18650 3.7v 2600maH battery pack (single), momentary switch and speaker. Battery is fully charged. (I have two for swapping and both are fully charged). The NB is pre-wired (Thanks, Tim!) and everything is soldered and ready to put back into the hilt.

Here's my problem. I connect the battery and sometimes the boot up sound happens and it works just fine, other times it doesn't. Sometimes I put the battery into the holder and no boot sound. When the boot up sound doesn't happen, it will not work. Odd, right?

Here is what I have done so far:

Re wired everything.
Taken the battery holder out of the loop and just used a connector with open wires.
Switched back to my original Green Seoul P4 LED, just to see if the different voltage needs might work.
- All these things still give me a Sometimes Yes(it comes to life) and Most Times No(it doesn't) result.

Now I am beginning to think that I have either too high or too low a resistor. So if R=U/I, what is the forward voltage of the deep red LED? Does I = .7 because I should run this at 700mA? If I use the example from the NB Owner's Manual, I would have R = (3.7-2.5) / .7 Is that correct?


However, I don't want to kill my NB by getting the wrong resistor, hence my coming here to look for an answer.

Thanks!

DeckRoid

[Silver Serpent]

Your NB is safe if you use the wrong resistor. Your LED on the other hand, could be damaged if you use too low of a value.

The formula you're using for your resistor is the correct one. Following the formula, you should be using a 1.7 ohm resistor (1.8 is the next size up).

Most of the issues people experience with the NB are due to low battery levels, poor soldering, or the SD card. You've eliminated the battery issue and presumably the soldering issues. You might try removing the SD card (with battery removed!), backing it up to your computer, and then reformatting it and reloading the files. Often times that will solve your issue.

[FenderBender]

Pics? Where in the circuit are you putting your resistor?

[deckroid]

Ok. Update!

I pulled the sounds down to my PC, then formatted then put 'em back. Same issue. So, I went back into my box of wires and started with all new JST connectors from the pre-wired NB to the various bits n pieces. Fixed. Somewhere something wasn't connecting just right. So, should I use a larger resistor? I have a 5W 1ohm cement style resistor and it seems to do the job fine...

Thanks for all the help!

[Silver Serpent]

If the LED hasn't blown, and is still bright, then you *might* be fine. You're overdriving that Rebel Deep Red LED by quite a bit with the 1ohm resistor. Personally, I would swap out the resistor for a 1.8 ohm or a 1.5 ohm.

The 1 ohm is fine for the P4 green.

[deckroid]

I am headed to the Radio Hack today. I thought I had one... no such luck.

Thanks again for all the help