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.
> >
>