Polarized Capacitor on schematic question

[silentblackhat]

I am making the voltage regulator schematic that is shown below. I see that the .1uF cap isnt polarized but the 1uf cap is. i wasnt able to find any polarized(well any cap that has a + and - shown on the cap casing). i did find a cap that was 1uF but doenst seen to be polarized like this schematic needs, will this work anyways with a nonpolarized 1uF cap?

I can, if needed, put some caps in series that are polarized that will have a total of 1uf(or close to it) but i dont really want to do that.



i am using this voltage reglator to step down my 13.4 volt supply of my cars system to step it down to 9v. i am using a heatsink that i took off my broken xbox motherboard...its plenty big enough, also has a fan on it

[myhrrhleine]

Yes,
non-polar caps will work

[silentblackhat]

alright thanks, i was hoping so, cuz i couldnt find anything below 4.7uf that was polarized.


I see on the LM317 packaget that the input voltage is 28 volts...is that what it will run at or will it run off of 14.4 for the voltage in?

[poobah]

It will run fine at 12 to 15 Volts in, with 9 Volts going out that is...

[silentblackhat]

well its built now, hope it works lol.

[poobah]

It should... don't expect it to cure your noise... it will knock down some.

[silentblackhat]

it works. yea i knew it wouldnt knock down the noise all the way, i just wanted a 9v power supply to it after realizing that:-).

[AndrewT]

Hi,
I'm a bit late but your comment

some caps in series that are polarized that will have a total of 1uf

will not work.

Resistors in series add up using ordinary arithmetic.
Capacitors in parallel add up, again using ordinary arithmetic.

Resistors in parallel use a formula to determine their effective resistance. It just happens that the same formula is used to calculate the effective capacitance for capacitors in series.

Here it is
Reffective=R1*R2/(R1+R2) for R1//R2
Ceffective =C1*C2/(C1+C2) for C1+C2 in series.

If more than two resistors in parallel or more than two capacitors in series are used then the formula becomes
Reffective=1/(1/R1+1/R2+1/R3+...)
Ceffective=1/(1/C1+1/C2+1/C3+...)
BTW. these last two formulae apply to pairs as well, but they take a little longer to calculate.

Finally you can use a higher voltage capacitor wherever a lower voltage is specified. Similarly you can use a non polarised capacitor wherever a polarised is specified. However there is a caveat:- the characteristics of the different types are very different. The designer may have selected a particular characteristic of the type specified to ensure correct operation of the circuit.

[Enzo]

So he puts two 2uf caps back to back in series to get 1uf. Why wouldn't that work?

That 1uf isn't critical, I see no reason the 4.7uf wouldn't work there.

[silentblackhat]

So he puts two 2uf caps back to back in series to get 1uf. Why wouldn't that work?

thats what i was thinking. i know the formulas for adding up the total measurement of a series of components. i was saying to put the 2 caps in series that will have the overall total of 1uF.

I have had to do this a LOT of times. Just as radio shack gave me a bad set of resistors(the 220ohm ones i got didnt even let any current flow through them) so i took my old alarm clock apart to get 2-100ohm resistors, and used 2-15ohm resistors all in series to get 230ohms, close enough to 240 from what i see. I am also a car audio installer so i deal with wiring subs and speakers in different ways to put different loads on an amp every day. on other projects i have had to put a few 100uF caps wired in parallel to have a total of 200uF. Anyways, its allready built and it works fine now; its perfect for what i need it for. I made it to power a LM386 based microphone amp.