Picking the right Capacitors for my voltage regulator

[Sulla]

I want to build a voltage regulator to power my think geek sound system off the 12v batteries I am using for the rest of the systems. This will be used to give my 1:1 R2 a voice. (see link to blog in my signature.)

Here's the drawing I put together of the circuit.

I am shopping for the electrolytic capacitors now and had a question: If I want a .1uF 12v and a .33uF 24v would that be the same as 3uF and 33uF?

 

[exoray]

If I want a .1uF 12v and a .33uF 24v would that be the same as 3uF and 33uF?

No...

.1uf and .33uf are the values...

Voltage rating isn't important as long as it's in excess of the maximum it will encounter...

Get the .1uf at whatever voltage in excess of 6 volts
Get the .33uf at whatever voltage in excess of 12 volts

You will probably find in those low values that most are well in excess of the voltage you need...

But one thing to note the caps are filtering off the noise on the line and smoothing the current, different values still filter and smooth so even with different values you can get decent results... The .1uf and .33uf have pretty much become the standard though in that application...

 

[Sulla]

Thanks. Now to find the darned things. I can't seem to find .1uf and .33uf in any voltage...

 

[exoray]

Thanks. Now to find the darned things. I can't seem to find .1uf and .33uf in any voltage...

Where are you shopping? They are common values found just about everywhere except Radio Shack...

 

[exoray]

Mouser has tons of different brands and what not, this is just a link to two... There are of course a dozen different brands and prices I just grabbed two that were on the same page and on the lower end of the price scale...

SEA0R1M1HBK-0407P Lelon Aluminum Electrolytic Capacitors - Leaded

SEA0R33M1HBK-0407P Lelon Aluminum Electrolytic Capacitors - Leaded

http://www.mouser.com/catalog/catalogUSD/642/766.pdf

If you want to get fancy you can explore the higher priced low leak capacitors, as well but they are likely not necessary...

 

[Sulla]

I am blind. Thank you exoray, for you have shewn me the light!

 

[Sulla]

Looks like I have a radioshack 7805 in my tool box. I'd like to go ahead and order a 7806. What's the big difference between these?

7806 regulator

 

[exoray]

The 7805 is 5 volts the 7806 is 6 volts... Also take note of polarity when you order the 7806, some manufacture have been known to rotate the legs vs the traditional center ground found on 7805s... Just something to pay attention to, also a heat sink wouldn't be a bad idea, you can get a cheap clip on one like this...

http://www.mouser.com/ProductDetail...=sGAEpiMZZMttgyDkZ5WiuipPLxMG8spXNed4tot/944=

 

[Sulla]

So long as I know which leg is ground and white it up properly, just about any 7806 will get me the 6 volts I need?

 

[exoray]

So long as I know which leg is ground and white it up properly, just about any 7806 will get me the 6 volts I need?

Yeah, just verify with the data sheet before you wire it up, most are center ground but every so often some manufacture tosses in a wild card...

 

[jwrjr]

Normally, for a "78xx" series regulator :
a. the middle leg and the mounting tab are both connected to ground. But check the data sheet to be sure.
b. The 0.1 and 0.33uf capacitors are noise filters. The exact values are not critical. Just make sure that they are rated for higher voltages than what you are going to connect to them.
Higher value capacitos are also desirable in addition to the 0.1uf and 0.33 uf capacitors (sort of like "shock absorbers" on a car). Higher values like 470 or 1000 uf would be good since this is for an audio circuit.