They only noted "No UV" on datasheets but i didnt see any information for RFI consideration on design guides but there are lots of power-led product designers. So whats the trick for proper design? 2006/2/24, Bob Axtell : > > A comment about these super LEDS: they belt out a horrific amount of RFI, > in > amounts that can't be contained unless extensive shielding is used. > > It was one of the most disappointing contract I ever had- it simply > could NOT be > made to pass FCC radiation specs. > > --Bob > > > G=F6khan SEVER wrote: > > >I have confirmed that the correct Vf bin code ranges in 3.51 - 3.75[V] > for > >my white Luxeon III Emitter power led. I have to confess that my mind a > >little bit confused at this stage. After taking account the proper Vf > value > >i decided to use max Vf value in my calculations (or do i have to choose > the > >typical 3.6V value?) and based on the > >"DS45 Luxeon III Emitter" datasheets' page 12 "Forward Current > >Characteristics" figure; "i power the luxeon 3 white emitter with 0.7[A] > i > >can get max normalized luminous flux". So i chose 0.7[A] as a second > >parameter of simple equation. That makes R =3D (24 - 6x3.6[V]) / 0.7[A] > >=3D 3.4[Ohm] (i will chose proper approximate R value for that) The > >dissipated > >power will be ~2.5[W] in this configuration. I think i have to lower the > R > >value a-bit for maximum capacity. I will try my simple experiment > tomorrow > >morning. Do you think the result predictable, in other words do we say > that > >we get stable 0.7[A] current or at the start we get 0.5[A] and increasing > to > >0.7[A] slowly? > > > >Another question for red color Lux3 power leds; Whats the wiser solution > to > >get the best current / normalized luminous flux trade-off? ( If i want > to > >get maximum flux i have to drive the led at 1400[mA] but that will cause > >overload on dissipated power and if i drive the circuitry with avarage > >current i will only get half of available radiation. Whats wrong with > that? > > > >I've lost a bit in this lighter area. Hope you clarify the dark areas... > > > >2006/2/23, William Chops Westfield : > > > > > >>I think you have fallen victim to two pieces of misleading data. > >> > >>First of all, the Vf spec of an LED is somewhere on the "knee" > >>of the voltage applied vs current conducted curve. If you apply > >>a current source whose max voltage is exactly Vf, you'll be on > >>that knee instead of in the "current limitting" range where you > >>want to be. Your supply of 24V only allows 0.1V "extra" for > >>each of your LEDs, which may not be enough to get them "ON" all > >>the way. (I'm not saying this QUITE right; we might get into > >>another "voltage across vs current through" debate.) > >> > >>More seriously, you're interpreting a Vf spec for TYPICAL > >>performance as what you'll actually see in practice. If you > >>look at the Luxeon document "Luxeon Product Binning and Labeling" > >>(), and in particular the > >>section of Vf binning, you'll see that a white Lux III CAN have > >>a Vf as high as 4.47V (or as low as 3.03V, which is quite a range. > >>(the datasheet has the full range even for 700mA)) Even if > >>you have the "middle" bin ("L") you could have Vf as high as 3.99V. > >>If you have a full reel, you can check which bin you have. I don't > >>think individual emitters are marked, though. If you have even a > >>couple of emitters in a higher Vf bin, you're going to run over > >>the 24V of total Vf you can get away with (or at least be even > >>further in that "knee" that I was talking about.) Also, you > >>junction temperature isn't going to be 25C at that sort of drive > >>(although this appears to be helping you; thus the warmup to > >>higher current.) > >> > >>Easiest solution: can you tweak the power supply output up via > >>some adjustment or remote sense capability? (OTOH, I think > >>1A current is pushing a Lux III quite a bit. That's close to > >>4W even at typical Vf...) Note that each instance of your > >>light bar will need separate tweaking. > >> > >>The rather broad range of luxeon characteristics seems to be a > >>bit of a sore point among the lighting crowd. Apparently you > >>have to be really BIG customer before you can ask for particular > >>bins instead of taking your chances... > >> > >>BillW > >> > >> > >> > > > -- > Note: To protect our network, > attachments must be sent to > attach@engineer.cotse.net . > 1-520-850-1673 USA/Canada > http://beam.to/azengineer > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist