From: Steve & Jeanne Keith (cckw@attbi.com)
Date: Thu May 01 2003 - 04:53:47 PDT
I use to design power supplies with these 78xx and 79xx regulators.
They will shutdown from over current or over temp. As someone
stated, the power dissipation in Watts is what will get to them 1st.
They need to be heat sunk using a mica washer and special thermal
compound to transfer as much heat as possible.
You should also put on each .01-.1 mf capacitor between the input terminal
and the ground terminal and the output terminal and the ground terminal.
They have a tendency to become an oscillator and that causes problems!
JC Whitney sells a version of this for gas gauges. It is mounted on a bar
that has a hole in it to attach to the gas gauge. The other end of the bar
has a stud to attach the power feed for the gauge. There is a wire coming
off the bar that needs to be grounded. Theyse units run about $18 and are
probably worth it when using 12v on a 6v vehicle.
Steve AKA Dr Deuce
----- Original Message -----
From: "TA2 CNU" <ta4cnu@hotmail.com>
To: "Military Vehicles Mailing List" <mil-veh@mil-veh.org>
Sent: Thursday, May 01, 2003 7:16 AM
Subject: Re: [MV] 6volts from 12 or 12v from 24 volts
>
>
>
>
> two or more 78XX or 79XX can be used in parallel, if the outputs are
> connected to a terminal with a i.e. 0.2 Ohm 5Watts resitor; more adviced
to
> use power transistors after the unit... then it gets complicated...
>
> ta2cce
>
>
>
>
>
>
> >From: David Cole <DavidCole@tk7.net>
> >To: "Military Vehicles Mailing List" <mil-veh@mil-veh.org>
> >Subject: Re: [MV] 6volts from 12 or 12v from 24 volts
> >Date: Wed, 30 Apr 2003 23:16:08 -0500
> >
> >I've used those before but in a controlled situation - ie. soldered into
a
> >PC board, feeding some ICs, etc. How do they standup to overloads, and
> >electrical noise. If they are rated for 1 amp, do they open circuit at 2
> >amps, etc?
> >
> >Dave
> >
> >On Wed, 30 Apr 2003 10:37:16 -0700 (PDT), w7ls <w7ls@blarg.net> wrote:
> >
> >>Yes, those will work. They are available in higher power packages, under
> >>different numbers. If you draw more juice through them for more lights
> >>or whatever, they will give off more heat, so a heatsink is a must. See
> >>Digikey.com, Jameco.com, Bgmicro.com, or if you're really desperate,
> >>Radio Shack. Jim
> >>
> >>"TA2 CNU" <ta4cnu@hotmail.com> wrote:
> >>
> >>>LM 78XX (xx= 06 for 6 volts, 12 for 12 volts)(negative ground)
> >>>
> >>>a simple transistor like chip can be used for getting 6 volts from 12
> >>>volts or 24 volts and 12 volts from 24 volts; but up to 1/2 amps. A
> >>>decent cooling fin will be needed...! (will cut out in case it gets too
> >>>hot).
> >>>
> >>>this is a three legged item :
> >>>left leg + volts in,
> >>>mid leg - gronund,
> >>>right leg + volts out.
> >>>
> >>>also:
> >>>LM 79xx (xx= 06 for 6 volts, 12 for 12 volts)(positive ground)
> >>>
> >>>
> >>>
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> >
> >
> >
> >--
> >Dave
> >
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>
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