How can we identify which values are more desirable on a capacitor in a circuit?
Is it just bigger is better or is there more to it than that? All I can understand so far is that you want to be close but over the circuit voltage for better performance, but what about the uF?
>>1017576
It depends on what the capacitor is used for in the circuit.
>>1017576
You had better be shitposting
>>1017579
I'm an idiot, feel free to judge me.
>>1017578
I want to use it with an inductor to reduce ripple in my speaker system I'm building.
I have parts from dead PSUs I can use so I'm pretty lucky in that regard, but I don't want to fuck my circuit up. I want best results
>>1017645
if its just a tank then you want it to be big enough to smooth out spikes but not so big that it draws too much current on startup that destroys the feeding circuit
if its part of a tuned filter then you want a specific value for the frequency you want to filter
>>1017645
>I want to use it with an inductor to reduce ripple in my speaker system I'm building.
then this applies -V-
>>1017682
>if its just a tank then you want it to be big enough to smooth out spikes but not so big that it draws too much current on startup that destroys the feeding circuit
>>1017576
>close but over the circuit voltage for better performance, but what about the uF?
Use the suggested or more uF but don't go crazy more.
Must be rated at more than the peak voltage seen in the circuit you're filtering.
>>1017723
>My circuit will be 5v, I remember reading about how the higher voltage the capacitor is(compared to the circuit) the less effective it is. True?
Not 'less effective', just bigger. There needs to be more separation between the plates to handle the voltage. wider separation lowers the inherent capacitance, so the cap must be bigger for the same value if the construction is otherwise the same.
>How do I understand uF to know what values will be good for my circuit?
Oh Lordy. So we're doing your homework for you....
>>1017727
Could you maybe provide a noob easy link so I can figure it out then?
I don't want you to tell me what values I should go for, but rather to help me understand what they mean so I can do it myself in the future regardless what circuit I'll be working on.
>>1017735
google [power supply theory]
The more current you device draws from the power supply the larger effective capacitance you need.
>>1017735
>Could you maybe provide a noob easy link so I can figure it out then?
Could you tell us what you're actually doing? Is this in a crossover, a power supply, a filter, what? Got schematics?
"I'm building a car and I need a bolt. What kind of bolt should I get?"
>>1017750
"I heard bigger bolts are not as good. Is this true?"
>>1017750
I'm building a set of speakers, the amp I'm using is a cheap class d amp and I want to kill the buzzing sound by reducing ripple as much as possible
>>1017753
>I'm building a set of speakers, the amp I'm using is a cheap class d amp and I want to kill the buzzing sound by reducing ripple as much as possible
so you're using 'a capacitor'.
"My car makes a funny noise. I want to use a bolt to make it stop. What kind of bolt do I need?"
>>1017753
>I'm building a set of speakers, the amp I'm using is a cheap class d amp and I want to kill the buzzing sound by reducing ripple as much as possible
You realize that the audio is, itself, 'a kind of ripple', right?
>>1017755
Using a small capacitor and inductor I was able to almost fully neutralize the buzzing sound, but it's still there rather faintly when the speaker is running off a wall wart instead of batteries.
I assumed that means it was just ripple from cheap circuitry.
>>1017757
Yes but does it sound like "dzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz dzdzdzdzzzzzzzzzzzzzzz"?
>>1017576
>(for audio power input supply filtering)
>Is it just bigger is better or is there more to it than that?
I only know a bit about it,,,,, but there is more to it than that.
For one, to reach any value of capacitance you can use either one big capacitor or a bunch of little ones.
The difference is that the one big capacitor will have a higher ESR than a group of little ones that total the same value, and having a lower ESR is better in this instance.
Pic related: an audio power input capacitor filtering array on aliexpress that uses 100 little caps.
You can find other boards on there (from other sellers) that are similar but with less caps: 20, 40, 60 or whatever.
-------
This subject is typically called "audio PI filtering" in Google, the PI standing for Power Input. As you are trying to smooth the input power for the amp.
One forum post is here:
http://diyaudioprojects.com/Forum/viewtopic.php?f=5&t=3184
there are others.
>>1017782
>I assumed that means it was just ripple from cheap circuitry.
OK, self powered speakers. You could in fact be getting 60Hz noise if they're cheap. Are they grounded?
>>1017576
If you want to stabilize voltage then "the bigger is better" and "the faster the better" (https://en.wikipedia.org/wiki/Equivalent_series_resistance).
Your electrolytic caps are the slowest.
Also, it it important how close to other components the capacitor is located – wires/tracks have some impedance as well.
>>1017849
Woah there Tex. This guy knows that when you flip a light switch, the light comes on. And he can tell a capacitor from a bolt.
Let's figure out for sure what the problem is before designing a complex bridge snubber for him.
>>1017576
its highly dependent on the circuit in question
some are used for ripple filtering, some for dc normalization, these are normally electrolytic ones used in ac/dc to dc power supplies
some are used as sort of a current limiter, these a normally film capacitors used on low power ac input supplies
some are used in timing circuits where the (dis)charging time of the cap matters
some are used to offset the phase in ac supplies
the only way to really get it all it to check out different circuits with them in effect and try to figure out why those caps are used in there
here is a "for dummies" vid
>https://www.youtube.com/watch?v=QuBpHacowqo
>>1017792
That's a lot of capacitors.
I'm working on a similar project to op. Usually you pair a capacitor with an indictor for the filtering effect.
Would any old inductor be fine?
>>1021313
>Usually you pair a wheel with a tire for rolling effect. Would any old tire be fine?
>>1021319
T-t-thanks...
>>1021313
>I'm working on a similar project to op. Usually you pair a capacitor with an indictor for the filtering effect.
>Would any old inductor be fine?
No.
First off--the inductor would need to be wound with wire that could withstand the amount of current draw that the power supply would be supplying.
Secondly, you're thinking of an RCL-type circuit, and those aren't used for power supplies anymore. But they used to be....
Pic related--
Top image: this is one type of (simplified) power supply for a stereo tube amp. The goal was that each channel would be resistant to "stealing" power from the other channel's supply. Back then tubes were very expensive, so they used this sort of circuit because it only required using one rectifier tube and not two. The inductors L1 and L2 slowed down current between the two channels' capacitors. (I could not find a pic online so I drew this from ancient memory and it may not be 100% correct, but anyway...)
Middle image: this is a modern stereo power supply. Diodes are cheap now, so they just have two full-wave bridges charging up two sets of capacitors, and neither channel can draw power off the others'. There is no inductors required on the output side.
Bottom image: if you just want to smooth out a single DC power supply, you just use one (or more) capacitors for that.
