How to step down 130 VDC using a LM7812?

How can I step down 130 VDC to 12 VDC using an LM 7812. As the 130 VDC
battery pak loses voltage I want to maintain the 12 VDC.

 

You can't. The LM7812 has a maximum input voltage of 35V. To step down from
130VDC to 12VDC you will need either a discrete build linear- or a switching
(buck) regulator.

petrus bitbyter

 

OK Thanks. Can you tell me how to connect the circuit using 24 VDC?

 

Did you try to find the info at all?
Look here: http://www.southwest.com.au/~jfuller/electronics/regulators.htm

 

Yes, thanks, I had read the info at that website. I was confused
because I had been told to use the LM7812 by someone who I thought was
knowledgeable. I am new to this field.

 

The 7812 has an "IN" (for up to 30 volts pin 1) and an "OUT" (12 volts
regulated pin 3).
The common (pin 2) or GND is shared between the two.
With a battery you won't need the large input capacitor.
Regards,
Tom

 

You also need to consider bolting the 7812 to a large heat sink.

You haven't what current you what to supply but for the sake of argument
assume that it is 1A.

You have a 24V source and you are delivering 12V. This means that the
difference of 12V will be across the 7812. With 1A being supplied this
means that 7812 will be disipating 12W (12V x 1A) which will mostly be
turned into heat. This may not seem much compared with everyday domestic
appliances but for an electronics component it is a lot. Without an
effective way to get rid of this unwanted power (heat) the 7812 will cook
and probably fail.

Cheers,

Nigel

 

A heat sink is definitely called for.
Tom

 

The device will draw 50 t0 100 mA.