# Question regarding capacitor size



## Skeletor (Mar 27, 2022)

Hello!

When populating a board, how do you determine if a capacitor is too big?

I've got a 100uf 50v capacitor that will kind of  fit, but some of the other components around it have to be slightly tilted to make it work.  Is this acceptable or is the capacitor too big?

Also, do the capacitors have to sit flush with the pcb or can then "float" over resistors?

Sorry for the dumb questions, but I was having a little trouble searching the forum to find an answer.

Thank you I'm advance.


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## Barry (Mar 27, 2022)

What board are you working on? It should be fine


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## fig (Mar 27, 2022)

+1 to Barry (always). 

Good question!

They can float or even bend. They can go on the back of the board if room permits (mind the polarity).


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## Skeletor (Mar 27, 2022)

Barry said:


> What board are you working on? It should be fine



I'm populating the muzzle board, and I got the resistors all in. I was moving on to the capacitors and wanted to test fit them to make sure they'd work.  I started with the 100uf and wasn't sure if they were too big or not.  My second concern with them is if they will be too big to put the two inputs jacks on the sides.

I also discovered I got the wrong 1uf capacitors too. I got the round polarized ones, and I guess I needed the box film ones.  Lol there is 100% a learning curve to all this.

Thank you!


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## Skeletor (Mar 27, 2022)

fig said:


> +1 to Barry (always).
> 
> Good question!
> 
> They can float or even bend. They can go on the back of the board if room permits (mind the polarity).


Ahh. Nice. I tried looking for some pictures and everyone's boards look perfect, so then I tried searching for an answer and couldn't find one.  I'm glad to know it doesn't have to be perfect because mine look like I was trying to solder on the back of a flatbed driving 50 mph down an unpaved road. Lol

Thabk you!


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## Steve973 (Mar 27, 2022)

I built the muzzle board, and I was wondering about capacitor size, too.  The three electrolytics on my board are a bit bigger than the PCB footprint allows, so I had to lift mine up a bit to clear the resistors.  

I also wonder if it is ever preferrable to use smaller (or larger) electrolytic caps in a particular situation, excluding voltage-specific situations.


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## fig (Mar 27, 2022)

Steve973 said:


> I built the muzzle board, and I was wondering about capacitor size, too.  The three electrolytics on my board are a bit bigger than the PCB footprint allows, so I had to lift mine up a bit to clear the resistors.
> 
> I also wonder if it is ever preferrable to use smaller (or larger) electrolytic caps in a particular situation, excluding voltage-specific situations.


It's all about the voltage and package size. Voltage should be at least 1.5 x _applied voltage_. Bear in mind, even if you are powering a board with 9VDC, many circuits utilize a charge pump to increase that, so any components receiving that voltage should be rated as such.  Most of the ECs will have pads around 3mm pitch (or lead spacing) so use that when shopping. Also check the diameter of the silkscreen or the space provided for the cap.
If you are uncertain about a particular cap, just ask and someone will chime in.


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## Skeletor (Mar 27, 2022)

fig said:


> It's all about the voltage and package size. Voltage should be at least 1.5 x _applied voltage_. Bear in mind, even if you are powering a board with 9VDC, many circuits utilize a charge pump to increase that, so any components receiving that voltage should be rated as such.  Most of the ECs will have pads around 3mm pitch (or lead spacing) so use that when shopping. Also check the diameter of the silkscreen or the space provided for the cap.
> If you are uncertain about a particular cap, just ask and someone will chime in.



I apologize if this is a basic question, but how do you determine the voltage you need.  I've just been getting 50 or 100v ones because I figure those had to be big enough.  Now I see that they can be TOO big.

I understand these use 9v connections but how do figure out how that is modified by charge pumps?


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## fig (Mar 27, 2022)

These are great questions. It was helpful for me to get a fundamental understanding of a schematic and the components needed to build a circuit. Also, it's most often noted on the build doc if anything above a nominal 16VDC rating is required. I'd suggest that builders who are not confident with component selection not opt to build a release that does not have supporting documentation until they have become more familiar with components in general.


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## Barry (Mar 27, 2022)

I typically try to buy electrolytics at 35V then 50V if 35 isn't available, I do have some 16V I picked up years ago when I was doing pedal mods that didn't require anything more


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## fig (Mar 27, 2022)

Barry said:


> I typically try to buy electrolytics at 35V then 50V if 35 isn't available, I do have some 16V I picked up years ago when I was doing pedal mods that didn't require anything more


_Years ago, _I couldn't have pointed out a capacitor  
You and the others have been a tremendous resource and just plain fun to _be_ _around_.


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## TravisM (Mar 27, 2022)

Also, you can bend the leads with pliers or tweezers if the pitch is off on the particular component you have. For capacitors, I try my best to find a non-electrolytic and non-multilayer ceramic just because I don't want to have to potentially replace a failed cap if I can keep from it. If you can't find a film cap I'll try to get tantalum or silver mica, just remember to mind the polarity with tantalum.

Humidity can cause electrolytic caps to go bad a bit faster than normal. I had a few go bad on the airbag controller in a miata years ago that I had to swap out. The airbag light would come on when the humidity got high and when I got the board out, the caps had started leaking, so in short, always wear a seatbelt.


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## fig (Mar 27, 2022)

Here's a sampling from the stash..cans omitted.


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## mybud (Mar 28, 2022)

fig said:


> Here's a sampling from the stash..cans omitted.


Tropical fish, boy oh boy!


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## Feral Feline (Mar 28, 2022)

fig said:


> Here's a sampling from the stash..cans omitted.


The really nice thing is, Fig always brings enough candy to share with the whole class!


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## andare (Mar 28, 2022)

Silver mica and tantalum caps are very expensive locally. Does anybody have a cheaper source?
I tried doing a search on Mouser and as always I got lost in the options


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## fig (Mar 28, 2022)

andare said:


> Silver mica and tantalum caps are very expensive locally. Does anybody have a cheaper source?
> I tried doing a search on Mouser and as always I got lost in the options


Electronic Goldmine runs daily sales that often include various types of capacitors. They wont magically have that one value you need to finish a project (unless you have more luck than I), but if you check regularly, you can piece together a nice stash. The mini-SM cap in the pic above came from one of those specials. Always mind the package size with SM, as many are too large to be practical.






						Electronic Goldmine
					






					www.goldmine-elec-products.com
				








						Electronic Goldmine
					






					www.goldmine-elec-products.com
				




Now I don't need everyone buying up all my deals so save me some  (j/k)

As @Feral Feline mentioned I'm more than happy to share my inventory with a friend in need. Hi, I'm Tim. 👋


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