LED - difference between red and blue

[gilbert]

Does anybody know the difference between the red and blue LEDs? I was
trying to make a flashing light to the front of my bicycle and tried
to use a flasher that originally worked fine with three red LEDs. It
doesnt show anything with the blue LEDs on,even after the original red
ones have been disconnected. Do you guys think there is a simple way
to solve this - like putting in a resistor or increasing the voltage
from two to three AA batteries? The blue LEDs, four of them, now work
fine on two batteries (AA), only, of course, they do not flash.
Please answer me in e-mail too.
Thanks
Gilbert

 

[Jeroen]

blue LEDs need more voltage to work, so I guess the flasher circuit does not
deliver the full voltage.

"gilbert" <gaubin@hotmail.com> wrote in message
news:c87ab623.0406061253.6e764e1e@posting.google.com...

Does anybody know the difference between the red and blue LEDs? I was
trying to make a flashing light to the front of my bicycle and tried
to use a flasher that originally worked fine with three red LEDs. It
doesnt show anything with the blue LEDs on,even after the original red
ones have been disconnected. Do you guys think there is a simple way
to solve this - like putting in a resistor or increasing the voltage
from two to three AA batteries? The blue LEDs, four of them, now work
fine on two batteries (AA), only, of course, they do not flash.
Please answer me in e-mail too.
Thanks
Gilbert

 

[gilbert]

"Jeroen" <dev@null.com> wrote in message news:<40c3ab8c$0$37789$e4fe514c@news.xs4all.nl>...

blue LEDs need more voltage to work, so I guess the flasher circuit does not
deliver the full voltage.

That's strange. I tell you why. I had a functioning blue fashing

arrangement earlier, with a cheap flasher that I bought for 99 cents
in Los Angeles in the 99 cents store. When I bought it, it was red,
and didn't work very well. It was not very luminous, and I figured
that this was a bad batch, that's why they sell it for 99 cents. I
put on the blue LEDs parallel to he existing red ones, and indeed, in
accordance with your idea, the blue ones did not light up, while the
red ones continued to flash.So I took off the red ones and the blue
ones started to flash all right.
The thing was working fine on the bicycle for several months. Then,
one day, it stopped flashing (but if I remember correctly, the light
was still on, continuously; I am not sure about this). Figuring that
the flasher was broken, I threw it out, and connected the blue LEDs
(five at the time) to two AA batteries. What happened next, was very
strange. The light was on, but the batteries got drained (or so it
seemed) in a couple of days. The thing seemed short circuited,
somewhere. I suspected rain water getting in somewhere but couldn't
find anything. Finally, I disconnected one blue LED and the remaining
four now work just fine. That LED was somehow short circuited
internally, partially.
So I went out to buy another flasher for 99 cents. This one seems to
be better, not from the bad batch that was not very bright. But the
blue LEDs do not light up.
Since the red lights on the new flasher are brighter than on the
previous one, it would seem that the voltage coming out from the
flasher is higher. Nevertheless, the blue don't light up, although
they did with the previous, seemingly weaker flasher. So I believe it
is not the voltage. So I was wondering if you can think of something
else? I don't know much about LEDs, I don't even know how they work
and what happens when you fry them.
Any ideas, anybody? If it turns out the voltage being too low, would
it get higher if I put three AA batteries on the input of the flasher,
or would it just ruin the flashing circuit?

 

[Tim Auton]

gaubin@hotmail.com (gilbert) wrote:
[snip]

The thing was working fine on the bicycle for several months. Then,
one day, it stopped flashing (but if I remember correctly, the light
was still on, continuously; I am not sure about this). Figuring that
the flasher was broken, I threw it out, and connected the blue LEDs
(five at the time) to two AA batteries. What happened next, was very
strange. The light was on, but the batteries got drained (or so it
seemed) in a couple of days. The thing seemed short circuited,
somewhere.

Did you have a current limiting resistor in there somewhere?


Tim
--
Love is a travelator.

 

[JeffM]

I was trying to make a flashing light to the front of my bicycle
...originally worked fine with three red LEDs.
It doesnt show anything with the blue LEDs on
Gilbert

Forward-facing red lights on a non-emergency vehicle
and blue lights of any kind on a non-police vehicle
are most certainly illegal.

 

[Don Klipstein]

In art. <c87ab623.0406070942.229bf22@posting.google.com>, gilbert wrote:

That's strange. I tell you why. I had a functioning blue fashing
arrangement earlier, with a cheap flasher that I bought for 99 cents
in Los Angeles in the 99 cents store. When I bought it, it was red,
and didn't work very well. It was not very luminous, and I figured
that this was a bad batch, that's why they sell it for 99 cents. I
put on the blue LEDs parallel to he existing red ones, and indeed, in
accordance with your idea, the blue ones did not light up, while the
red ones continued to flash.So I took off the red ones and the blue
ones started to flash all right.
The thing was working fine on the bicycle for several months. Then,
one day, it stopped flashing (but if I remember correctly, the light
was still on, continuously; I am not sure about this). Figuring that
the flasher was broken, I threw it out, and connected the blue LEDs
(five at the time) to two AA batteries. What happened next, was very
strange. The light was on, but the batteries got drained (or so it
seemed) in a couple of days. The thing seemed short circuited,
somewhere. I suspected rain water getting in somewhere but couldn't
find anything. Finally, I disconnected one blue LED and the remaining
four now work just fine. That LED was somehow short circuited
internally, partially.

Most blue LEDs develop a partial short if they suffer damage from static
electricity. You can do this to a blue LED even if the static electricity
is not enough to produce a visible or audible spark. I have also seen
blue LEDs develop partial shorts if overheated by excessive current, but I
doubt that happened here.

So I went out to buy another flasher for 99 cents. This one seems to
be better, not from the bad batch that was not very bright. But the
blue LEDs do not light up.
Since the red lights on the new flasher are brighter than on the
previous one, it would seem that the voltage coming out from the
flasher is higher. Nevertheless, the blue don't light up, although
they did with the previous, seemingly weaker flasher. So I believe it
is not the voltage. So I was wondering if you can think of something
else? I don't know much about LEDs, I don't even know how they work
and what happens when you fry them.
Any ideas, anybody? If it turns out the voltage being too low, would
it get higher if I put three AA batteries on the input of the flasher,
or would it just ruin the flashing circuit?

Maybe the new flasher had less output voltage but more current or more
efficient red LEDs than the old flasher.

Possible the blue LEDs were damaged by static electricity or lack of a
dropping resistor, but I doubt two AA cells will cook most blue LEDs
without a dropping resistor. But two AA cells will have their voltage too
low to operate most blue LEDs while a majority of their charge is not yet
consumed.

- Don Klipstein (don@misty.com)