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Thread: ???s about some flashlight leds, voltage etc

  1. #1

    Default ???s about some flashlight leds, voltage etc

    With the stay at home stuff kicking ive been trying to placate my OCD ADD etc nervious issues with hobby projects,

    I have used leds as long as i can remember but still have a lot to learn,

    In this case im repurposing for lighting on a custom large scale rc buggy build,
    I had several small flashlights that plugged into a cars cig lighter to charge, while charging they had a bright blue light near the reflector edge,

    When turned on they had a very bright white single led, so when they stopped working and i took one apart the battery appears to be 3 large button cells shrunk wrapped together
    3.6 volts so i assume when the light was on it was fed full volts,
    What i did was wired the blue and white leds in series hit them with 6 volts and both light up,

    My question is this very bright "flashlight" white leds the same mid 3 v as other white leds?
    Will it draw a lot of juice to use it?


    Next question,
    Here is a genetic imported led light for rc cars, its all wired up to go,


    https://www.killerrc.com/collections...d-headlight-ea

    They advertise that it will work on 3 to 10 v
    that has me a bit confused,

    Most rc lights plug into the vehicles receiver which most run 6 v and output 6 v to lights,

    I assumed this light with 12 leds was wired in 4 sets of 3 in series to fed each led about 3 v.

    Anyway, how can this light have such a wide voltage range 3 - 10 volts wouldnt 3 be low and 10 be high, out of goldilocks zone?

    Thanks for into,
    Stay safe,
    Cheers
    b

  2. #2
    Flashaholic
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    Default Re: ???s about some flashlight leds, voltage etc

    Quote Originally Posted by the13bats View Post


    Next question,
    Here is a genetic imported led light for rc cars, its all wired up to go,


    https://www.killerrc.com/collections...d-headlight-ea

    They advertise that it will work on 3 to 10 v
    that has me a bit confused,

    Most rc lights plug into the vehicles receiver which most run 6 v and output 6 v to lights,

    I assumed this light with 12 leds was wired in 4 sets of 3 in series to fed each led about 3 v.

    Anyway, how can this light have such a wide voltage range 3 - 10 volts wouldnt 3 be low and 10 be high, out of goldilocks zone?

    Thanks for into,
    Stay safe,
    Cheers
    b
    Just a guess but possibly it uses a switching-type boost converter which can have a wide input range,
    but uses constant-current output to maintain brightness across input range. These are common for
    backlight LED drivers for LCDs, etc.

    What's more likely than all 12 LEDs in series (~36v) is two parallel strings of 6 (~18v). If the LEDs are well
    matched, this should work.

    Dave

  3. #3
    Flashaholic* DIWdiver's Avatar
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    Default Re: ???s about some flashlight leds, voltage etc

    Yes, the flashlight will have a 3V white LED in it. Most white LEDs are actually blue(ish) LEDs with phosphors to turn some of the blue to other colors needed to make white.

    Any LED driven by a voltage source will need a 'driver' of some sort. In your flashlight, the 'driver' was likely the internal resistance of the batteries. The killerrc light almost certainly has a proper electronic current-regulated driver in it, as Dave_H says.

    Now, as to whether it will take "a lot of juice" to run the flashlight LED, that depends on your definition, and how you drive it. The button cells in the flashlight were probably NiCad (maybe NiMH, depending on age), and they were probably built cheaply, thus having relatively high internal resistance. LED current on a full charge was probably not more than a few hundred milliamps, maybe less. How bright were they?

  4. #4

    Default Re: ???s about some flashlight leds, voltage etc

    Thanks guys,

    Ive been into the rc hobby well over 40 years and my thing is mostly large scale gas vehicles,
    To me a fail safe is a must, we tackled that very redundantly in the old days now i use these,

    https://www.killerrc.com/collections...switch-car-kit

    i find its in person presentation low end but they work well and The led light output is pretty cool as it flashes a warning when the voltage of the receiver pack drops to a set level
    It has a 6 volt output,
    The fog lights killer sells at their mark up are a generic import item far cheaper on ebay for the very same item,

    Anyway, the buggy im working on now has 5 roof lights so i just wired the 5 yellow amber leds in series and it works fine,
    As far as the flash light i wanted to use it like a tear drop spot light seen on police cars.
    So as i said i wired its white main led with it blue that used to show it was charging in series so i could just run that 6v straight to it,

    I should have mentioned i bypassed the flashlights charging etc circuit board in other words i am just using its leds in the case thats now modded to look like a little spot light,

    When it was a flashlight its battery a ni-mh 80mah lasted a fairly long time, i never timed it, very bright,

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