Homebrew PCBs

----- 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