Refining a simple 12v regulator circuit for maximum utility?

[brad]

Slajeune's Ruby Tuby Power Supply has become one of the building blocks of all my circuits lately. Basically, it's a 7812 +12V 1A Voltage Regulator with 1000uF decoupling caps on it's input and output.  Although it works fine, I'd like to make the regulator as robust as possible so it can survive all my screw-ups 

I'm not 100% sure what kind of internal protection the regulator has, but would adding a diode in parallel to the regulator protect it against shorts?  Are the large value elecros really necessary, or could smaller tants/film caps be used instead?

[KMS]

You should keep the 1000uf caps......the bigger the caps the smoother the output......but it is hard to tell after a certain point.

You can find a schematic for diode protection for the LM317 here
http://pdf1.alldatasheet.com/datasheet-pdf/view/11662/ONSEMI/LM317.html

Scroll down to the bottom of page 7

That type of diode protection should work for any regulator.

[Sir H C]

Should have all the protection built in.  I would think the output capacitance is a bit high, usually there is a limit after which it is not good as it slows down the regulator too much. 

[Andre]

A rule of thumb is to use 1000uF per Ampere, so in case of 7812, which can deliver 1A maximum, 1000uF is sufficient.
You only need one of this size at the input of the voltage regulator. The one on the output can be much smaller, maybe 100uF.

It is also wise to use 10uF tantaliums on both the input and output, to prevent oscillation of the voltage regulator.
They need to mounted to the 7812 , or any other in the 78 or 79 series, as close as possible.
Since this type of regulator has both overload and thermal protection, abuse is permitted.
It won't break easily.

Andre

[brad]

Thanks for the replies!  So he 10uF tants need to be soldered TO the in/out lugs in addition to the regular electros?  Wow...that's one filtered supply 

I'm also thinking of adding a DPDT toggle switch to the perfboard that would allow for switching between positive and negative tip adaptors...

[brett]

A rule of thumb is to use 1000uF per Ampere

If I recall correctly, the rule of thumb quoted at the ESP site is 2200uF per amp.  But in that case, they're talking about hi-fi as well as guitar and other amps, and applications that are unregulated.  If you're drawing low current through a regulator, smaller caps will do fine (especially on the exit - I routinely use 470uF post-regulator).

Also, the 78XX series application notes show 0.1uF caps as the de-coupling caps.  Tantalums might be ok, but the guys and gals that write those sheets are very smart cookies.
cheers