[Soekris] net4801 Multi-IO and LCD backlighting

[J Moore]

On Sat, Sep 25, 2004 at 04:57:07PM +0100, the unit calling itself Chris Boot wrote:
> >>
> >>I'd like to control the backlight on my LCD panel, when I get it, via
> >>the Multi-IO controller. I know I can't drive the backlight straight
> >>off one of the data lines (!) so I'm going to need a transistor, I'm
> >>guessing. I am, however, no electronics expert, so I'd like some help
> >>here! Could anyone draw up some schematics for me, and/or tell me what
> >>sort of transistor I need?
> >
> >Which LCD panel - you got a part number?
> >
> It's a part I'll be getting from the UK electronics store Maplin, N30AZ 
> in their catalog. Apparently it's a DEM 20485 SYH-LY panel, 20x4 with 
> LED backlighting.

The data sheet at Maplin's website is not clear, but it appears the
required current-limiting resistor for the backlighting LEDs may be 
on the board. So in the best case, you would connect a +5 VDC supply to 
pin 16, and a switch (e.g. 2N2222A as suggested previously) to pin 15, 
and the backlighting will work. In the worst case, you'll burn out the 
backlighting LEDs because the module is not configured properly.

The problem is that "Display Elektronik GmBH" documentation (the PDF
file at Maplin's website) indicates there are some "strapping options"
(which may be in place as 'solder bridges'), but they do not clearly
define how this works. If it were my money, I wouldn't buy shit from a
bunch of f**g dumb-ass Krauts that can't create a decent data sheet, and
have a super-lame website.

If you have to use this part, I'd recommend you Google usenet to try to
find someone who has actually used it, or ask Maplin if they can supply
you with a schematic. If you find better data on this part let me know &
I'll draw something up for you...

HTH,
Jay