[sdiy] MG-1 first mods, VC res

[Scott Gravenhorst]

"Roy J. Tellason" <rtellason at blazenet.net> wrote:
>On Sunday 31 October 2004 12:36 pm, Scott Gravenhorst wrote:
>> "jamhoney" <jmahoney at gate.net> wrote:
>> >> ... 35V is the MAXIMUM
>> >> for all 78xx and 79xx regulators, except the 7824 and 7924.
>> >
>> >Can you cascade 2 regulators? Like, transformer --> 7824 --> 7815? I
>> >believe it's okay, but...
>>
>> Well, you *can*, but the 7815 will get pretty warm.  These regulators
>> are happiest with the input voltage just above the dropout voltage plus
>> the regulator output voltage.  How much above dropout+output depends on
>> several things, including ripple at the input.  I try to maintain input
>> about 3 volts above the regulator's output voltage.  The more input
>> voltage you apply, the more the regulator's shunt transistor has to
>> "waste" current - creating heat.
>
>Those are not shunt regulators...

I stand corrected, however doing this cascaded regulator thing still
presents heat problems.  The better way is to use a proper spec'd
transformer and filter.


---------------------------------------------------------
- Where merit is not rewarded, excellence fades.
- Hydrogen is pointless without solar.
- What good are laws that only lawyers understand?
- The media's credibility should always be questioned.
- The only good terrorist is a dead terrorist.
- Governments do nothing well, save collect taxes.

-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
-- Linux Rex         | RedWebMail by RedStarWare
-- FatMan: home1.gte.net/res0658s/fatman/
-- NonFatMan: home1.gte.net/res0658s/electronics/
-- Autodidactic Master of Arcane and Hidden Knowledge.