Resistor Question ..Nano biscotti and a Luxeon 3-up rb/rb/rb.

[Defcon4]

First let me say, sorry if this has been asked or if its a dumb question.
I'm a bit uncertain and would like to get the advice of the pros before proceeding.

I'm building a PVC saber and using NB card for sound.

Power source is 2x14500 for a total of 7.4 volts.

http://img.photobucket.com/albums/v153/DEFCON4/spkr2aa_zps8d8d667f.jpg

The led is a 3-up royal blue/royal blue/royal blue. This led is bridged/wired in serial.

http://img.photobucket.com/albums/v153/DEFCON4/3-UPROYALBLUE_zps3ceac9ce.jpg

When calculating for the resistor for the led do I use the total VF for all 3 leds (10.2 vf) ..or just one? 3.4vf

Also, Please advise if you think I need to make changes to some of the components as well.

Thanks in advance.

Albert

[Forgetful Jedi Knight]

Well, first off, the NB won't handle a 7.4V pack, it can only handle up to 5.5V.

Your best bet is to use an 18650 3.7V battery. You can then wire 2 of the 3 dice in parallel and run them at 1A (1000 mA). That will be pretty bright. In that setup, the battery pack Vf is 3.7V and the LED Vf is 3.4. YOU would have to put a resistor on each (+) wire to each die you wire up.

[Defcon4]

Well, first off, the NB won't handle a 7.4V pack, it can only handle up to 5.5V.

Your best bet is to use an 18650 3.7V battery. You can then wire 2 of the 3 dice in parallel and run them at 1A (1000 mA). That will be pretty bright. In that setup, the battery pack Vf is 3.7V and the LED Vf is 3.4. YOU would have to put a resistor on each (+) wire to each die you wire up.

Thank you, jedi

I was more screwed up than I realized. lol

Off to the store to look for some components. I appreciate your help very much.

Albert

[Jay-gon Jinn]

Well, first off, the NB won't handle a 7.4V pack, it can only handle up to 5.5V.

Your best bet is to use an 18650 3.7V battery. You can then wire 2 of the 3 dice in parallel and run them at 1A (1000 mA). That will be pretty bright. In that setup, the battery pack Vf is 3.7V and the LED Vf is 3.4. YOU would have to put a resistor on each (+) wire to each die you wire up.If he puts them in parallel, and then gives the pair 1000ma, each die will only get 500ma. If you calculate the resistor value for 2000ma, you'll be giving the two led's 1000ma each, and get a much better result.

[Forgetful Jedi Knight]

If he puts them in parallel, and then gives the pair 1000ma, each die will only get 500ma. If you calculate the resistor value for 2000ma, you'll be giving the two led's 1000ma each, and get a much better result.

He was suppose to give each DIE the 1000 ma. You are right though, I wasn't as clear as I could have been.

[FenderBender]

I would wire two 1ohm 2watt resistors in parallel to bring it down to .5ohm and let it ride full drive 3 up. That will blind you.

[dannv]

For Series wiring, see http://led.linear1.org/led.wiz . It shows wiring in parallel with a 1 ohm 2 watt resistor for each die. Useful site for this typo of thing.

[FenderBender]

When you calculate based on the total MA usage, and not the needs of individual dice, you get like .00001 ohms which is next to zero. Normally, I'd say to not even use a resistor, but it will pull the voltage down too fast and also heat up the board transistor and you'll get mad false swings. A 2w 1 ohm on the set of three, or 2 of them wired in parallel (twist the leads together and solder) for .5ohm (brighter option), will work just fine. The LED vf and the source voltage are really close here, what you're trying to do is just keep them from drawing over the limit that the board will pass through, and to keep the battery voltage from dropping to fast.

[Johannes Huber]

Fenderbender: Going back to the comment on a pair of 1ohm2Watt resistors in parallel allowing you to run it "full drive 3 up", are you referring to being able to run all 3 LEDs at 1000mA? I ask since I've been swearing over being limited to a total of 2000mA running parallel on both of my last 2 sabers, leading to a little less than 700mA per LED (the limit being due to not wanting to go over the 2000mA current limit Mr. Plecter put in as the maximum for the NB) and I'd love to run them brighter on future builds (both were gifts to friends scattered across Texas and Canada so I can't change those but...). My only frustration with the NB (I love the board otherwise, amazingly tough and incredibly versatile) has been the limit on current. I know that the Petit Crouton can get around it with the pex but not the NB. Any advice you can give is very much appreciated. Thanks!

[dannv]

I believe the nano board is limited to 2000mA. You need to stay below that. As to what to use for resistors, follow the link I posted above and play with it. Tell it to output in a wiring diagram and you'll get a picture of what to put where.

[Forgetful Jedi Knight]

Fenderbender: Going back to the comment on a pair of 1ohm2Watt resistors in parallel allowing you to run it "full drive 3 up", are you referring to being able to run all 3 LEDs at 1000mA? I ask since I've been swearing over being limited to a total of 2000mA running parallel on both of my last 2 sabers, leading to a little less than 700mA per LED (the limit being due to not wanting to go over the 2000mA current limit Mr. Plecter put in as the maximum for the NB) and I'd love to run them brighter on future builds (both were gifts to friends scattered across Texas and Canada so I can't change those but...). My only frustration with the NB (I love the board otherwise, amazingly tough and incredibly versatile) has been the limit on current. I know that the Petit Crouton can get around it with the pex but not the NB. Any advice you can give is very much appreciated. Thanks!

Johannes, The NB was not really designed/meant to run Tri-dice setups. With that said, IF you try to run all three dice, you won't be able to run them at 1000 mA, unless you have a battery solution that reliably discharges 3 Amps. They will run at whatever the battery discharge is divided by 3. So, as an example, if the discharge rate is 2400 mA - divide that by 3 and each die should get roughly 800 mA. It's not easy to determine the current discharge rates, and they do vary over the life of a battery.

So the choice you have is 2 at 1A vs 3 at something less than 1A - and less run time.

[FenderBender]

The NB is limited to 2.5A, but that is little enough difference. Still, 2.5/3=800ma per die which will not be dim by any measure. However, if you're accomplished with your soldering you can piggy back another transistor on top of the one on the board to double the pass through;) Or....you can use a pex (same transistor), you just have to wire it the same way you would with a PC or CF, from the PWM output.

[Johannes Huber]

Really? I can use a PEX? (slobber, drool. Time for some red sauce on pasta!) Now to go back through the NB manual (may need to print a new copy, mine is...heavily used) and locate the PWM. I haven't seen it referred to as that term, but just as put wire "X" in this slot;)... and give this a try on NB build #4. Like I said, I love the NB for it's versatility and elegant size and if this works, it gets even more attractive. Many, many thanks!

[Arsies]

Just be sure to post your wiring diagram once you have it running, I think it will help so many people like me that may want to do the same or close to :)

[Darth Ryo]

The NB is limited to 2.5A, but that is little enough difference. Still, 2.5/3=800ma per die which will not be dim by any measure. However, if you're accomplished with your soldering you can piggy back another transistor on top of the one on the board to double the pass through;) Or....you can use a pex (same transistor), you just have to wire it the same way you would with a PC or CF, from the PWM output.

That's very interesting, I'll look into that "another transistor" solution when time comes ^^ thanks for sharing this!

[Defcon4]

Thank you,

I appreciate all the great information.. and I have taken notes for future projects. Couldn't do it with out you guys..

I have finally completed the build on this R2D2 themed saber. I know R2 wasn't a Jedi, but this is for my grandson's Christmas and I thought it would be fun. lol
Its loaded with an R2D2 boot sound and it has a silver and blue color scheme. I'll post some pictures of the saber.

[Defcon4]

This is a simple PVC saber, made from a 1 1/2" extension tube and a 1" pvc pipe for the blade holder. In place of o-rings I have 1 1/2 " square cut slip joint washers. The metal rings are 1 1/2 " curtain rod rings.

VIDEO

http://img.photobucket.com/albums/v153/DEFCON4/th_R2D2SABER_zpse24b834f.jpg (http://img.photobucket.com/albums/v153/DEFCON4/R2D2SABER_zpse24b834f.mp4)

http://img.photobucket.com/albums/v153/DEFCON4/R2SABER3_zpsd687db87.jpg

http://img.photobucket.com/albums/v153/DEFCON4/R2SABER1_zps80a3dd10.jpg

http://img.photobucket.com/albums/v153/DEFCON4/R2SABER2_zpse7cbfc5c.jpg