ComputerVoltageSources

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.
>