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Re: TR2 - converting to negative earth

To: Randall Young <ryoung@NAVCOMTECH.COM>, "triumphs@autox.team.net" <triumphs@autox.team.net>
Subject: Re: TR2 - converting to negative earth
From: Doug Hamilton <douglasehamilton@shaw.ca>
Date: Wed, 27 Mar 2002 11:26:13 -0700
References: <NCBBKDNEEKEOHAOIIOIIEEBAGBAA.ryoung@navcomtech.com>
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:0.9.4) Gecko/20011128 Netscape6/6.2.1
After working for 14 of the last 18 years on British and Swedish 
military equipment where allot of the drawings are +0 volts reference 
and all other voltages quoted as a negative values to reference and 
every component appears to be installed backwards etc. You'd think I'd 
remember that you can create a +/- reference to zero volts.  Based on 
the JCWittney's description of the box it didn't sound like what they 
where doing. Good thing I'm working on software now and not hardware any 
more
I best get a coffee before replying in the future.
On the flip side the box is about the same price as a one wire 
alternator which would be a better investment if you where using your 
sound system allot.

Doug Hamilton

Randall Young wrote:

>>I'd be very careful with one of these converters they don't
>>address the real problem of installing a negative ground radio in
>>a positive ground vehicle. And that is your antenna still grounds
>>to the body thus creating a dead short between the positive earth
>>car chassis and the negative earth radio chassis.
>>
>
>Doug, I'm sorry, but that is simply not correct.  The converters work by
>generating +12v relative to your car's ground, which is what the radio
>requires to work.  The radio chassis and antenna are both still grounded to
>the car, no short exists.
>
>A lot of people seem to find this concept confusing, there's nothing magic
>about connecting a "positive ground" to a "negative ground" as long as the
>opposite terminals do not touch.  A better way to look at it is that the
>car's chassis is zero volts (0V).  A "positive ground" system has the
>battery positive terminal connected to ground, hence the other terminal
>becomes -12V.  But, there's no reason you can't connect a second battery
>with it's negative terminal to ground, which would make it's other terminal
>+12V.  And, you'd get 24V between the two battery terminals.  This is
>exactly the way the "ground converters" work, they create a "virtual
>battery" with it's negative terminal to ground.
>
>It's actually a very common configuration in electronics, your PC (or Mac)
>for example most likely has both +5v and -5v voltages (along with a host of
>others).
>
>Randall

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