How to step down 130 VDC using a LM7812?

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

schreef in bericht news: snipped-for-privacy@f14g2000cwb.googlegroups.com...

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

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.

Did you try to find the info at all? Look here:

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.