I think this is for current regulation - to maximise battery life, and
get a consistent tint - the colour of white LEDs varies with current
as the phosphor characteristic is nonlinear, giving a different
balance between the blue LED colour and the yellow phosphor colour.=20

You can drive them with resistors in most applications, as slight
colour changes are not often too important. =20

On Mon, 9 Jul 2001 17:14:46 +0200, you wrote:

>It seems from the Bulb life thread that there are a lot of drivers ICs =
for white LEDs
>is that for any special reason? I mean your regular red LED never had a =
driver IC..
>are the white LEDs "special" in some way, or can I drive them with a =
series resistor=20
>like I do with all the other LEDs?
>
>I'm not sure how many LEDs one would need to give sufficient lite..I was=
 thinking 4 maybe..and a couple of red ones for the tail light..
>you mentioned NiCd, I thought those could only be recharged when they =
were completly drained or you pretty much ruined them.
>
>I wasn't part of the Piclist at the time for thsoe free cells :/
>
>/Patrik
>----- Original Message -----=20
>From: "Roman Black" <fastvid@EZY.NET.AU>
>To: <PICLIST@MITVMA.MIT.EDU>
>Sent: Sunday, July 08, 2001 6:42 AM
>Subject: Re: [EE]: LED bicycle headlight
>
>
>> Patrik Husfloen wrote:
>> >
>> > Neat, I was looking to do the same thing, though I have a =
dynamo/generator driving my bulbs.
>> > so I guess I'd need some rectifier circuit, using a backup cap to =
give som glow while stopped might be nice also.
>> > too bad I have no clue on electronics :)
>>=20
>>=20
>> Hi Patrik, what about a small NiCd or NiMH
>> battery pack (like the free ones someone gave
>> to piclisters before?) Small and lightweight.
>>=20
>> That gives continued glow when the bicycle is
>> stopped, steadier glow when moving and is a very
>> simple way of protecting the LED headlight from
>> overvoltage.
>>=20
>> You need the NiCd battery, LED and it's resistor,
>> and maybe a protect zener and on/off switch
>> would round it out nicely. Nothing too complicated
>> there.:o)
>> -Roman
>>=20
>> --
>> http://www.piclist.com hint: The PICList is archived three different
>> ways.  See http://www.piclist.com/#archives for details.
>>=20
>>=20

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listserv@mitvma.mit.edu with SET PICList DIGEST in the body