Re: Replacing a car globe with a series of LEDs
- From: "Arfa Daily" <arfa.daily@xxxxxxxxxxxx>
- Date: Sun, 14 Aug 2005 18:13:43 GMT
You shouldn't need a resistor - in theory - but when multiple LEDs are
connected in series like this, they are often fed via a simple constant
current source. This can be easily and cheaply realised with two or three
components. This will allow you to set the desired current through your
chain of LEDs for optimum performance ie light output vs life. Also, your
assertion that the individual LED currents will add up, is wrong. If you set
the LED current for say 30mA, and connect 6 LEDs in series, that same
current of 30mA will pass thru all 6. If, however, you connect them in
parallel, the current will add up, but you will definitely then need a
series reistor - 330 ohms at half a watt would do nicely. This would be my
preferred way of doing it anyway as, if one of the LEDs fails in your series
chain, they all go out, whereas if one fails in the parallel setup, the
others stay on, allbeit at changed brightness if a simple resistor is used
for the current limiting.
As far as needing to load the bike's electrics up to simulate the former
lamp load, this will depend on whether the flasher unit is a thermal
relaxation switch, based on a bimetal strip, or an electronically switched
relay. If it's the latter, no additional load other than the LEDs will be
needed - except you might want to put some in anyway to help keep the relay
contacts clean. If the former, then the full load of the original lamps will
be needed, otherwise the flasher unit won't work at all. If the simulated
load is too light, the flashers will run too fast.
Geoff
"slepax" <slepax@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:Q5LLe.185053$Di2.106330@xxxxxxxxxxxxxxxxxxxxxxxxx
> Hey all,
>
> This is not really a repair question, but most of you probably have
> electronic skills to answer this question.
>
> Short description of the problem: I want to use a series of LEDs to
> replace the turn signal indicator globe on my bike.
>
> My bike battery outputs 12.5V, and currently, the bike uses a 12V/10W
> globe (on each side). I intend to replace each globe by connecting 6
> LEDs in a row, so that way the total voltage required for all LEDs
> would be ~13.8V (a single LED consumes 2.0-2.6V, so 6x~2.3V=13.8V).
>
> So here comes my first question. Am I assuming correctly that because
> I have a total of 6 LEDs in a row (~13.8V) I
> don?t need a resistor
> [b:6e8628ea4d]before[/b:6e8628ea4d] the LEDs?
>
> Next, a single globe consumes 0.83A (10W/12V=0.83A) while all the LEDs
> together consume less than half (~0.05Ax6=0.30A). So here comes my
> second question, do I need to put a high-power resistor in
> [b:6e8628ea4d]parallel[/b:6e8628ea4d] to the LEDs to match the
> current consumption compared to the globe?
>
> Sorry it?s long, but I would appreciate you help.
>
> Cheers,
> Ronen
>
.
- References:
- Replacing a car globe with a series of LEDs
- From: slepax
- Replacing a car globe with a series of LEDs
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