ComputerVoltageSources

We need to get an LCD module and see what a reasonable backlight 
current is.  I've not used one yet at the full current spec. I can buy 
one from Mouser.  I wonder what Paul did on the MOTM-650?

Dave


--- In ComputerVoltageSources@yahoogroups.com, "John Loffink" 
<jloffink@...> wrote:
>
> Forward voltage on the backlight is 4.2 volts.  It must have LEDs in 
series.
> Forward current is 160 mA.
> 
> Power dissipation for backlight from +15V is (15 V - 4.2 V) * 160 mA 
= 1.73
> Watts.  Ouch!  We could put a big clunky 5 Watt power resistor down, 
just
> don't put this next to a VCO. :-)
> 
> Power dissipation for backlight from +5V is (5 V - 4.2 V) * 160 mA =
 .128
> Watts.  Suggest we use a half watt resistor minimum.  Resistor is 0.
8 V /
> 160 mA = 5 ohms.
> 
> We need to account for systems without 5 volt power, so we'll need a 
jumper
> or stuffing option for a 1/2 watt or so regulator and multiple power
> connector options.
> 
> Seems like we should just power everything from the LCD support PCB 
local 5
> volts.
> 
> John Loffink
> The Microtonal Synthesis Web Site
> http://www.microtonal-synthesis.com
> The Wavemakers Synthesizer Web Site
> http://www.wavemakers-synth.com
> 
> 
> > -----Original Message-----
> > From: ComputerVoltageSources@yahoogroups.com
> > [mailto:ComputerVoltageSources@yahoogroups.com] On Behalf Of 
djbrow54
> >
> 
> > Alternatives for the +5 volt power are:
> > 1) Use the CVS PCB.  Power for the ATTINY2313 is 6 mA. The LCD
> > Assembly selected has a separate 2 pin connector for the 
backlight.
> > This could be powered from +15 volts with a current limit resistor 
or
> > from +5 volts with a current limit resistor if available from the
> > power supply.
> > 
> > 2) Local +5 volt regulation for the ATTINY2313 and power the 
backlight
> > from +15 volts with a current limit resistor.
> > 
> > 3) Power both the ATTINY2313 and backlight from +5 volts with a
> > current limit resistor if available from the power supply.
> >
>