The white LEDs have a rather high forward voltage (3.6V ?) so to drive them off one or two batteries you typically need some sort of DC-DC converter. Also by using current instead of voltage feedback, the converter can be quite efficient. Bob Ammerman RAm Systems (contract development of high performance, high function, low-level software) ----- Original Message ----- From: "Patrik Husfloen" To: Sent: Monday, July 09, 2001 11:14 AM Subject: Re: [EE]: LED bicycle headlight 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 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 ----- From: "Roman Black" To: 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 :) > > > Hi Patrik, what about a small NiCd or NiMH > battery pack (like the free ones someone gave > to piclisters before?) Small and lightweight. > > 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. > > 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 > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body