For those of you that have purchased a Lilliput
LCD screen, chances are you have an "egg"
laying around that you're not using. I'm
referring to the egg-shaped +12V regulator
that came with your Lilli that let's you
safely plug it into the cigarette lighter
of your car. It's job is to prevent Lilli
from dying due to high voltages and/or spikes
coming from your alternator. It normally
takes an input of +12v to +16v and turns
it into a +12v regulated output that drives
Lilli.
Well, if you've purchased a CarNetix CNX-P1260,
chances are you've hooked Lilli up in parallel
with your CarPC so that the P1260 powers
your CarPC AND your screen. If so, your egg
is gathering dust! Let's put it to use by
converting it to a +5V regulator for your
USB devices!! It's actually a pretty easy
mod and will prevent you from having to buy
something kludgy from Radio Shack or WalMart
(for another $25).
This mod will give you a +5V source that's
capable of providing up to 2 Amps of current
to your USB devices. This should be plenty
for most applications. But be careful, some
of the larger USB devices (like the Audigy
sound card) require 1 to 2 Amps all by themselves!
Make sure you know how much current your
devices need so that you don't burn Lilli
PCB!
Also note: the Lilli Eggulator was NOT designed
to provide 2 Amps of current! However, I
have tested this mod AT ROOM TEMPERATURE
at it seems to work pretty well (ie...no
smoke). The biggest problems are the Inductor
(large round black device with no markings)
and the "catch" diode (small rectangular
device mounted on the back side of the PCB).
These guys get pretty warm and will be the
first things to check if something fails.
Your mileage may vary.
Also note: the basic mod presented here provides
a CONSTANT (ie always ON) +5V source. When
connected as shown here, +5V will be present
on Pin 1 of J2 AT ANY TIME THE +12V INPUT
LINE (j1) IS CONNECTED TO YOUR BATTERY! What
this means is, if your USB devices will always
be powered with the basic mod! If you are
drawing 1-2 amps, you battery could be drained
VERY QUICKLY if your engine is not running.
It is recommended that, either limit your
USB device current drain to something very
low (100 mA or less) OR add a disconnect
switch at the output of this mod (Pin 1 of
J2).
FOR EXPERTS ONLY: We have also presented
an advanced mod that shows you how to modify
the LilliPCB (ie cut 2 traces) and connect
the shutdown pin of the LM2596 to the DLYON
signal from the CNX-P1260. This will turn
off the +5V output when you turn off your
ignition so that your USB devices don't kill
your battery.....EXPERTS ONLY, PLEASE!
NOTE: Please take a close look at your egg-ulator
and make sure it is the same model as shown
in this mod. Also, make sure that the regulator
IC is an LM2596-12. If your eggulator is
not identical to what you see here, this
mod will not work! Don't try it.
***CAVEAT *** CAVEAT ***CEVEAT***
What we are about to show in this mod is
shown for the convenience of CarNetix customers.
It is recommended that you NOT implement
this mod if you do not have good electrical,
mechanical, and soldering skills! If you
damage your CNX-P1260 while making this mod,
your warranty is void. If you damage your
USB devices, we cannot be held responsible.
We have provided this information as a convenience
only and take no responsibility for performance
or proper operation of your CarPC, components,
or systems.
First, take the two screws out of the bottom
of the egg and open it. Look closely and
make sure it matches what you see here. If
not, do not attempt this mod. It won't work.
Next, remove the small circuit board from
the plastic case and look closely at the
large IC (regulator). It should be marked
"LM2596S-12" as shown here. If
not, do not attempt this mode. It will not
work!
If your IC is an LM2596-12, you can remove
it and replace it with an LM2596-5 (+5v version
of the regulator). Note that this will not
be a perfect match since the existing components
(mainly the inductor) in the circuit were
designed to be used with the +12V regulator,
but from our experience, it works well-enough
for someone desperate for +5V for their USB
devices!
You'll also notice that Lilliputians have
used a surface-mount device in a non-surface-mount
configuration. This was a plot to make our
lives more difficult. But alas! We will outsmart
the Lilliputians and use a "TO-220"
version of the LM2596-5!
Here's what the LM2596-5 TO-220 looks like
fresh from Digi-Key. The cost $4.30 each.
The first thing we want to do is mutilate
it a bit by straightening its legs.....like
so.
