Homebrew PCBs

The half angle is 10 degrees which is the half power point according
to the data sheet from Best Hong Kong. So if I want the two LEDs half
power point to fall halfway between them, that would be .25 inches. A
little trig gives me that the LEDs should be 1.4 inches  above the board. 

So I am pretty close to what a calculation will show. Of course 1.25
was just a guess, not a calculation. 


 
--- In Homebrew_PCBs@yahoogroups.com, "Leon" <leon355@...> wrote:
>
> ----- Original Message ----- 
> From: "javaguy11111" <javaguy11111@...>
> To: <Homebrew_PCBs@yahoogroups.com>
> Sent: Monday, March 03, 2008 2:12 PM
> Subject: [Homebrew_PCBs] Re: UV LED Test
> 
> 
> >I did a little more testing of UV LEDs this weekend. The LEDs are
> > plugged into a solderless breadboard and driven with a variable
> > external power supply I tried a 3x3 grid with 1 inch and .5 inch
> > spacing. The LEDs were run at 20mA and pulled about 10V.
> >
> > The 1 inch spacing at 1.25 inches above the board showed too much
> > variation in exposure. I would get areas of overexposure while other
> > areas would not get enough exposure. I tried times of 1,5 and 10
> > minutes. 10 minutes was way over exposed, 5 not so bad and 1 left some
> > areas okay, but other areas underexposed.
> >
> > I then did tests with .5 inch spacing with the LEDs at 1.25 inches
> > above the board. Uniformity of exposure was much better. I tried an
> > exposure time of 1 minute. I think I can drop that down to 45 seconds
> > as I still saw a little extra exposure in areas directly below the
LEDs.
> >
> > So I think for me .5 inch LED spacing is what I am going to use to get
> > uniformity. I will do a few more tests of increasing the distance to 2
> > inches above the board to see how that works.
> 
> From the light distribution in the data sheet, it should be possible to 
> calculate the optimum spacing for a given distance.
> 
> Leon
> --
> Leon Heller
> Amateur radio call-sign  G1HSM
> Yaesu FT-817ND transceiver
> Suzuki SV1000S motorcycle
> leon355@...
> http://www.geocities.com/leon_heller
>