wow........thanks for all the high tech imput!!.......Robb ----- Original Message ----- From: "Peter Rebaudo" <reba...@pacbell.net> To: "Silver list" <silver-list@eskimo.com> Sent: Wednesday, September 17, 2003 9:54 AM Subject: CS>LEDs
> Hi: > For LEDs of kinds : > <www.gilway.com> > <www.eLumexLEDs.com> > > Title: About LED's,Candelas and Watts. > > Although this is not strictly a CS subject I think it's a useful > adjuvant to it > If I am wrong please accept my apologies. > > I shall make some statements, they are at the best of my knowledge, > today. Of course comments and corrections are most welcome. > > Visible LED's are usually specified in Candela units. This units are > weighted to the human eye response. > When LED's are used for tissue irradiation the important Item is the > forward (Light going forward, not in all directions) radiant power, > expressed in Watts (or milliwatts) and since Watts x seconds = to > Joules, the dose should be expressed in Joules (watts-second). > > To obtain the radiant power from LED manufacturers has proven rather > difficult. So here are some numbers: (Values are approximations) > > MGMicro LED clusters (from used traffic signals) > Red probably 660nm, > At 1.8 volts, 20 mA, 600 mCd, 0.65 mW > 2.0 45 1000 1.37 > Approximates Gilway E168 > > Green probably 565 nm > At 2.2 Volts , 20mA, 300 mCd, 0.064 mW > 2.5 45 600 0.17 > Approximates Gilway E166 > > As can be seen from the above numbers although the red and the green > have the same "brightness" (600 mCd) the power emitted by the red is 10 > times that of the green. > This relationship approx. holds for all reds Vs green LED's. > Therefore the use of the candela measure can be misleading. > > Also LED's with wider view angles (2 Omega1/2) and the same Candela have > more power output than narrower ones. > > Infrared LED's are usually specified in milliwatts per steradian . > A steradian is a solid angle (3D's) which having its vertex at the > center of the sphere, cuts off a spherical surface area equal to the > square of the sphere radius. > So in a 1 meter radius sphere an angle of 1 steradian will encircle an > area of one square meter. > Here care must be exercised, when the specs said an LED has a 20 mW/sr. > It does not mean that if the power is measured in its center steradian > angle it will be 20 mW's, The power density will be equal to 20 mW/sr > only in the center one hundred of a steradian. > > So once again the thing that counts is: The total radiant power emitted > forward. > > Example: Giway IR LED # E24 specified at 20 mw/sr (typical) has the > following total power: > > At 1.4 Volts, 20 mA, 3.20 mW at zero distance from LED face. > 2.54 mW at 1.0 cm (into a 1cm detector) > 1.21 mW at 2.5 cm (into a 1cm detector) > > However if the power in the center 0.01 sr is measured and then is > multiplied by 100 it will equal to 20mW/sr. > > In my experience irradiation with IR(880) and Red (660nm) clusters seems > to help in a number of maladies. > > To build a powerful IR (72 LED's) cluster a kit can be purchased from > the maker <www.dalewheat.com> or from BGMicro. <www.bgmicro.com> > Complete kit $25.95 part # LED1069, Assembled and tested $35.95 LED 1070 . > A weather resistant enclosed version for $59.95. > > The PCB part # LED1070, $9.95 can be used to built a RED version using > Gilway #E184 LED's (660nm, 2000 mCd, min., 3500 mCd max.) Its power > output at the led face is: > At 1.85 V, 20 mA, 2.0 mW > 2.00 V, 36 mA 3.5 mW > 2.30 V, 60 mA 5.3 mW > For continuous wave Operation, 200 Ohms resistors can be used. > > For pulsed operation the circuit provide by Walter Cook at > <www.seanet.com/~waltc/page43.htm> is very useful. > > For extensive information on LED's and Laser Diodes, use and dosages see : > Therapeutic Lasers Theory and Practice, by G.David Baxter,. > Churchill Livingstone, Publisher. > > Last Comment:, Remember that: > > Power Density = Irradiance = Total Incident Power / Area. [Watts / cm^2] > Radiant Exposure = Energy Density = Total Incident Energy / Area. > [Joules / cm^2] = [Watts-sec/cm^2] > Radiant Exposure Also is equal to: > Total Power Density x Total Time of Irradiation [Watts/cm^2 x Seconds] > Walter's schematic produces a frequency of 7 Hz at 50% duty cycle. > Baxter states that a 4Hz frequency decreases sensitivity to pain > immediately, Walter's circuit can be easily altered by changing a couple > of components . > > Sincerely > > Peter R > > > > > -- > The silver-list is a moderated forum for discussion of colloidal silver. > > Instructions for unsubscribing may be found at: http://silverlist.org > > To post, address your message to: silver-list@eskimo.com > > Silver-list archive: http://escribe.com/health/thesilverlist/index.html > > List maintainer: Mike Devour <mdev...@eskimo.com> > >