Date: Fri, 13 Oct 2000 11:28:45 -0500
From: "Larry Williard" <[EMAIL PROTECTED]>
Subject: Re: Libretto Digest #1137
> Please, Larry, please stop running your Lib directly off the car battery.
I
> know computers, I know cars, I know this to be bad. $40 is not a lot for a
> proper adapter.>
> And by the way, 1/8" ( or any size ) phone plugs short out while being
> inserted. A better choice would be a coax power plug, a 2 or 4 pin jones
> plug, or a phonO plug.
> > Pres Waterman W2PW
> c/o Patchogue Motors, Inc.
> Long Island Ford and Kia dealer
Pres:
Your response is welcome, However being a electronics engineer for the
last 30 years and having checked carefully what goes on at the cig connector
with a scope. I will continue to use my system, if that's OK with you. I
have used this system for the last 3 years with 2 different laptops.
All "phone plugs" (which means the type used for ear phones, Im using a
mono one) do NOT short when connected. In fact I have not found any that do.
It wouldn't be too healthy for your equipment if they did. There are other
types that are designed to break before make or make before break but they
are NOT phone plugs. Some are even designed to be shorted without a plug
plugged into the connector, but NOT phone plugs. You can check this by
connecting a multimeter to the connector terminals and inserting a plug.
You can also use a "DC Power Plug" (coax style) but be careful! some of the
female connectors ARE shorted when no plug is inserted and its hard to find
a female in a round package, most are square. The idea was cheap and simple
and easy to build.
As for the car, It is a late model with good filtering at the cig plug
and the voltage is well regulated at 14.28v. at all Rpm's. Which is normal
for most cars made after 1985 or so. My Lib power supply is 14.98v. Most
adapters for car use do little or nothing to regulate the car voltage and
some just have a resistor and zener to lower the voltage to 12v, 10.8v, 9v
or some other voltage and some don't even have a zener, they are used for
cassettes, CD's or other devices to be used in a car. Many cell phone
adapters do nothing to the cars voltage except provide a connector for the
phone. Some charge the phone. The Lib computer's power supply regulator is
FAR better than that found in the average car radio, cassette player, or CD
and they have done pretty well.
I will admit that a regulated and fused adapter would be a safer system
but in my opinion is not necessary. My cig adapter is fused. The fuse wont
protect the Lib anyway. The biggest worry would be spikes (which you would
hear on your radio) and the possibility of an alternator failure. It would
also be more convent to have an extra cable. If you can find the adapter.
Have you ever scoped the 12v to 115v inverters that many people use to
run their laptops in the car? Scary. Id like to tear apart one of the
"proper" adapters to see just what is inside, if anything.
Larry Williard
c/o Orion Systems
A small testing company, In conjunction with Asic GmbH, We test and design
integrated circuits some of which are used in your cars.
We built and tested all of the first generation (80's) ABS break system IC's
made by VDO as well as automatic seat belt retractor IC's used on the
Mercedes and other cars and continue to test many IC's used in today's cars
as well as several used on the AirBus and other airplanes.
I do not wish to get into a Pi--ing contest about this and only offered
my solution and opinions. Like any opinions today. If you don't like it.
Don't use it.
Larry
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