using/protecting a LM7809

TitaniumHamster · Post by **TitaniumHamster** » Wed Jul 26, 2006 10:18 pm

Now, I'm new to this whole "DIY electronics" thing, so I'd like to know, other than connecting The original +30-9.1v to the LM7809, and connecting the ground and the 9v that leaves the LM7809, how do you protect the LM7809? All the other voltage regulators thrown around this site seem to need restitors and diodes and other such electronic "things" connected to them to get a steady signal, so what do I need for a LM7809?

In case you're curious, I need this to power my 64SS, becuse my "9v Wall Adaptor" actually outputs around 16v! That's the last time I trust China!

Post by **Skyone** » Wed Jul 26, 2006 10:39 pm

First off, it's input is 11.5v - 24v, not 9.1v - 30v. You don't really need to protect it, but you can control ripple to make the output EXACTLY 9v, but it's not worth it.

TitaniumHamster · Post by **TitaniumHamster** » Wed Jul 26, 2006 11:14 pm

Skyone wrote:First off, it's input is 11.5v - 24v, not 9.1v - 30v. You don't really need to protect it, but you can control ripple to make the output EXACTLY 9v, but it's not worth it.

So I just solder the corresponding wires to each respective spot? No 100uf caps, no diodes, no nothing? And this will make a steady 9v that won't one day just rise up and fry my batteries? Ok... I hope the 64SS doesnt catch on fire...

Post by **Skyone** » Wed Jul 26, 2006 11:24 pm

Haha, generally 78xx IC's are very steady, I wouldn't worry.

timmeh87 · Post by **timmeh87** » Thu Jul 27, 2006 9:45 am

it wouldnt hurt to put a capacitor on the output to save it from possible current spikes.

also, wall adapters will output the rated voltage at the rated current. if you are just measureing the voltage with an open circuit you can expect it to be much higher. i dont really see a reason to try to regulate it down.

vskid · Post by **vskid** » Thu Jul 27, 2006 9:51 am

timmeh87 wrote:also, wall adapters will output the rated voltage at the rated current. if you are just measureing the voltage with an open circuit you can expect it to be much higher. i dont really see a reason to try to regulate it down.

Ya, I had a 7.5v adapter that would output 12v under no load.