4aaa 6v power source, MR board, 1000mA cyan LED. Resistor needed?

[ShogunLogan]

Greetings all!

first off, would like to thank everyone on this board and Tim from TCSS for the wealth of knowledge on this site. I have been making heat sink sabers as a hobby for about a year now and soak up any and all information i can get from this place! I have been mostly a lurker but am trying to change that slowly.

I have been searching the forums now for a while and have heard that depending on the power source, if one uses a sound board, you dont need a resistor because there is one built in. I have also read on here that you can over power leds slightly and they work fine for the most part. So im hoping someone out there would know if i am using a MR soundboard would i be able to get away with using the TCSS 4aaa battery pack to power a cyan led, or should i use a resistor. also, would anyone know the specs on how much the MR board actually resists? would i be able to run other colors in the 700mA range or would those fry instantly.

I tried searching but was unable to find this answer and if someone could point me in the right direction, that would be great! I am still learning slowlyl, so go easy on me.

-Mark

[Obi1]

Some rumors are simply not true. You can use a 4aaa battery pack (totalling to around 6V), but please do not try to directly supply the MR board with that voltage, it might fry. My experience with TTL max rating is that they will probably tolerate up to 5.5V, anything above that is inviting disaster. But it's better to Limit the voltage to 5V. You can do that with a voltage regulator and some caps. The Hasbro board will neither limit the voltage to the LED(s), so resistors are definitely needed. With 3aaa's you would probably not need a resistor for a Cyan LED, cause it has a typical forward voltage of above 3V and although 3aaa should total to 4.5V, I've never seen any accus with more than 4.1V, and your LED can probably take that much overdrive (cannot comment on lifetime though). BUT 4aaa are too much, you need to limit the voltage somehow. As to current capability, I do not have the figures but my gut Feeling tells me the Habros could deliver 2A in total. Probably more, but I would not put my head on it. If that was the question regarding resisting. If you meant the Hasbro board acting as a resistor, see some lines above.
Hope I could make some points more clear! Better to ask than to sit frustrated above a damaged Hasbro board (I know how it feels...)

[ShogunLogan]

Thanks Obi for the advice!

Im not worried about frying the board as much as if i am getting all i can out of my led. i currently have a set up where i am running 6v through a MR board no problem but i am using a 2.2ohm 5w resistor for the white led. it seems a little less bright than my other sabers that are running the same set up with no sound and was curious as if maybe the board was zaping some of the juice.

I have read on here that the cheapo hasbro boards do not resist any current but the MR ones do and was wondering if any one has calculated by how much. Just looking to get the most out of my led without frying the system.

OR i could just do the smart thing by taking your advice and investing in some proper voltage battery packs, instead of running the risk of frying the system. Which is what i will more than likely do.

[Obi1]

I can tell from experience and experiments with the Hasbro boards, that the working principle of the cheapo and the not so cheapo boards is the same. You have transisors either fully on or fully off, current limits is done via resistors.
If you are afraid the board might eat some of the juice, measure the voltage wo/the LED when switched on. Due to the fact that the drive transistors have a channel resistance, called Rdson, it will eat up some voltage through the IR drop. Now of course nowadays this Rdson should be in the miliOhm range, but who knows what s***t Hasbro used to lower costs...so your theory might be right.

[Jay-gon Jinn]

Some rumors are simply not true. You can use a 4aaa battery pack (totalling to around 6V), but please do not try to directly supply the MR board with that voltage, it might fry. My experience with TTL max rating is that they will probably tolerate up to 5.5V, anything above that is inviting disaster. But it's better to Limit the voltage to 5V. You can do that with a voltage regulator and some caps. The Hasbro board will neither limit the voltage to the LED(s), so resistors are definitely needed. With 3aaa's you would probably not need a resistor for a Cyan LED, cause it has a typical forward voltage of above 3V and although 3aaa should total to 4.5V, I've never seen any accus with more than 4.1V, and your LED can probably take that much overdrive (cannot comment on lifetime though). BUT 4aaa are too much, you need to limit the voltage somehow. As to current capability, I do not have the figures but my gut Feeling tells me the Habros could deliver 2A in total. Probably more, but I would not put my head on it. If that was the question regarding resisting. If you meant the Hasbro board acting as a resistor, see some lines above.
Hope I could make some points more clear! Better to ask than to sit frustrated above a damaged Hasbro board (I know how it feels...)

It's not a rumor, those boards handle 6 volts just fine, I've done it myself over 50 times, never blown a board.

[Obi1]

I sincerely bow my head, in my philosophy experimental evidence always goes before dry theory. So this is proven not to be a rumor.
I also thank you for this info, I am just about to (try to) replace the 3xaaaa in my Vader Hasbro with 4xaaaa and room is limited, so I am grateful that I do not need to squeeze in additional components.

[Jay-gon Jinn]

Yeah, there was actually some members that did the actual testing back in 2006 and 2007 with bench top psu's and multiple battery set ups to measure just how much it took to release the "magic smoke" from the boards, and it was found to happen at 6.2-6.3 volts, so as long as you avoid the Lithium type of duracells and energizers (as they have a higher starting voltage out of the package), the boards will work just fine on 6 volts. Those boards were found to function best on on 4 NiMH AA's if you can fit them. There is a topic over on FX-Sabers that covered several of the boards and multiple battery cells/types with maximum current ratings and voltages, but every time I look for it, I cannot find it again. :P

I personally used 4-AAA's to power a saber of mine back then, and found them to die after about 20 minutes of play time...not so much fun. I would use a LI-Ion 18650 to power a cyan rebel directly from the board's outputs, no resistor, or if you want to, use about a 1ohm, 2watt just to be on the safe side.

EDIT:
found one of the posts with testing on MR FFX boards: http://www.fx-sabers.com/forum/index.php?topic=13978.0

[ShogunLogan]

Yeah, there was actually some members that did the actual testing back in 2006 and 2007 with bench top psu's and multiple battery set ups to measure just how much it took to release the "magic smoke" from the boards, and it was found to happen at 6.2-6.3 volts, so as long as you avoid the Lithium type of duracells and energizers (as they have a higher starting voltage out of the package), the boards will work just fine on 6 volts. Those boards were found to function best on on 4 NiMH AA's if you can fit them. There is a topic over on FX-Sabers that covered several of the boards and multiple battery cells/types with maximum current ratings and voltages, but every time I look for it, I cannot find it again. :P

I personally used 4-AAA's to power a saber of mine back then, and found them to die after about 20 minutes of play time...not so much fun. I would use a LI-Ion 18650 to power a cyan rebel directly from the board's outputs, no resistor, or if you want to, use about a 1ohm, 2watt just to be on the safe side.

EDIT:
found one of the posts with testing on MR FFX boards: http://www.fx-sabers.com/forum/index.php?topic=13978.0

Thank you for the information and the link! I read through the information and it is quite informative about those little boards. i would of never guessed they could handle 6.3 volts.

i also agree with you about the resistor. I had a 2.2ohm lying around from another project and used that just to be safe and am still getting some amazing brightness from the led. Didnt want to risk it until i upgrade to the LI-Ion 18650 as suggested from you guys.