I am terrible at math, so I just can not calculate the resistor I need. I will be using the PC 2.0, FoC, Tri-Rebel Star BBW, and 7.4v Li-ion 800mAh 14500 Battery Pack. What is the proper resistor in the store that I should get?
I am terrible at math, so I just can not calculate the resistor I need. I will be using the PC 2.0, FoC, Tri-Rebel Star BBW, and 7.4v Li-ion 800mAh 14500 Battery Pack. What is the proper resistor in the store that I should get?
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There are also resistor calculators available on the net. I use the one I found over at CandlepowerForums. It should be noted that these programs are usually developed by hobbyists, and should not be relied upon as the only source of information. Programs can have unknown flaws or bugs.
Aside from that, you might also check the forums for similar setups. The search function can narrow down your work considerably. I would look at FenderBender and other pro smiths. Sometimes you will find a complete build log that is relevant to the setup you want.
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All n00bs READ these first (PLEASE)!!!:
1. Forum Guidelines
2. FJK’s “Down and Dirty” guide to Ohm’s Law
"Yeah, yeah, I've heard it all before... you want blindingly bright, super loud, running 1138 blinkies off of the cheapest sound card you can find AND you want all of it to run on a battery the size of a dime, and run for a very, VERY long time. That one cracks me up every time..."
My email: fjk_tcss@yahoo.com
Okay, so I'm using the Tri-rebel star BBW. White is the FoC color. You say that I should use a different batter pack? Which one should I use? I should mention that I am going to have very little room in my hilt as I am using on of the blank blade holders which significantly reduces the amount of space available for electronics if I'm going to keep my hilt under 1 foot, so a larger battery pack is not possible.
Oh, and technically couldn't I just use this: 20mA DynaOhm™ Variable Resistor?
Sorry for sounding like such an amateur. I really have been on the saber scene for a while, I've just never used FoC before.
Last edited by Renaissance Jedi; 04-24-2013 at 08:53 PM.
Also, for reference, here is the internal view of the hilt.
Untitled.jpg
Sure, if you only want 20mA going to your FoC LED
The DynaOhm in the store is the same as the current regulator on Petit Crouton, it varies voltage to give the specified current to the LED it is attached to. On Petit Crouton this is whatever you set in the configuration file, but for the Dynaohm it is set to 20mA, purposed for driving small accent LEDs.
As for calculating your resistor, it's simple ohm's law (for which there is already a very extensive guide on this forum).
R=V/I
In other words, your resistance (in ohms) is equal to your desired voltage drop divided by your desired current (in amperes).
The white luxeon rebel has a Vf of 3.1V and can be run at 1A. This gives us the equation:
R=(7.4-3.1)/1
Hence:
R=4.3Ω
Now we need to calculate power so we don't burn out the resistor. We use the formula P=IV. Power (in watts) is equal to current (in amperes) multiplied by voltage.
P=(7.4-3.1)*1
P=4.3W
Therefore you need a 4.3Ω resistor with a power rating greater than or equal to 4.3W.
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Well... I won't really comment on the design, and if you don't have a lot of room, it is what it is.
For the original question, like Skott said, you will need the 4.7 Ohm,5W resistor that is sold in the store. I would recommend the 14650 pack IF you had the room.
TCSS MODERATOR
All n00bs READ these first (PLEASE)!!!:
1. Forum Guidelines
2. FJK’s “Down and Dirty” guide to Ohm’s Law
"Yeah, yeah, I've heard it all before... you want blindingly bright, super loud, running 1138 blinkies off of the cheapest sound card you can find AND you want all of it to run on a battery the size of a dime, and run for a very, VERY long time. That one cracks me up every time..."
My email: fjk_tcss@yahoo.com
Thank you to everyone who helped me out with my issue.
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