What does capacitance/voltage mean on this circuit?

Go To Last Post
29 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0


Hi there,

 

I'm designing a circuit to test a device and I ran into something that I haven't seen before - some of the capacitance values are divided by a voltage as shown in the picture.

 

 

It this just trying to tell me the voltage design value of the capacitor? Why do some capacitors have these values while some do not? 

 

[attachment embedded]

Attachment(s): 

This topic has a solution.

1010001010111101110111

Last Edited: Thu. Oct 28, 2021 - 08:42 AM
This reply has been marked as the solution. 
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

It means the capacitor is designed to work at voltages up to 25V.

 

Above that, the capacitor may be damaged; it might even explode.

 

Look at some capacitor datasheets for further details & examples.

 

Please see Tip #1 in my signature, below, for how to put the picture in the post - where we can see it (an admin has done it for you here - but you can do it yourself):

Top Tips:

  1. How to properly post source code - see: https://www.avrfreaks.net/comment... - also how to properly include images/pictures
  2. "Garbage" characters on a serial terminal are (almost?) invariably due to wrong baud rate - see: https://learn.sparkfun.com/tutorials/serial-communication
  3. Wrong baud rate is usually due to not running at the speed you thought; check by blinking a LED to see if you get the speed you expected
  4. Difference between a crystal, and a crystal oscillatorhttps://www.avrfreaks.net/comment...
  5. When your question is resolved, mark the solution: https://www.avrfreaks.net/comment...
  6. Beginner's "Getting Started" tips: https://www.avrfreaks.net/comment...
Last Edited: Thu. Oct 21, 2021 - 10:10 AM
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Hi awneal,

 

Thanks for clarifying. That is what I suspected. It's strange that they chose to include it in the circuit, isn't it? Usually when I add capacitors to a circuit I give them a decent safety factor anyway - I've never seen a circuit where it's explicitly stated. Any idea why they chose to include it for some capacitors and not for others?

 

I tried to add the image but I ran into the not authorized to view this page error. I'll try copy-pasting next time but I am on a Mac/Linux system, I don't have paint.

1010001010111101110111

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0


 

Mithrandir_ wrote:
It's strange that they chose to include it in the circuit, isn't it?

Not really - some do it; some don't.

 

You haven't said who "they" are, or what the context was.

 

I tried to add the image but I ran into the not authorized to view this page error.

Tip #1 covers that.

 

ADDENDUM

 

Here's an example that does both:

From: https://www.hobby-hour.com/elect...

 

They've put voltages on the ones where it's a key consideration, and not on ones where it's unlikely to be an issue.

 

ADDENDUM 2

 

Similarly for resistors:  generally, people don't tend to put the wattage on resistors in a schematic - except for ones where it's specifically important

 

Example:

https://www.circuitlib.com/index...

Top Tips:

  1. How to properly post source code - see: https://www.avrfreaks.net/comment... - also how to properly include images/pictures
  2. "Garbage" characters on a serial terminal are (almost?) invariably due to wrong baud rate - see: https://learn.sparkfun.com/tutorials/serial-communication
  3. Wrong baud rate is usually due to not running at the speed you thought; check by blinking a LED to see if you get the speed you expected
  4. Difference between a crystal, and a crystal oscillatorhttps://www.avrfreaks.net/comment...
  5. When your question is resolved, mark the solution: https://www.avrfreaks.net/comment...
  6. Beginner's "Getting Started" tips: https://www.avrfreaks.net/comment...
Last Edited: Thu. Oct 21, 2021 - 11:01 AM
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Mithrandir_ wrote:

It's strange that they chose to include it in the circuit, isn't it?

 

Not really. Any decent schematic CAD package will bring all that information, even down to part numbers, into the schematic so that the BOM (Bill Of Materials aka Parts List) can be automatically generated.

#1 Hardware Problem? https://www.avrfreaks.net/forum/...

#2 Hardware Problem? Read AVR042.

#3 All grounds are not created equal

#4 Have you proved your chip is running at xxMHz?

#5 "If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand."

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

That’s OK,the Elco polarized capacitor for main Vdc decoupling.Meanwhile the 0.1uF for IC decoupling.If that Vdc(5 Vdc) not the main reel then 22uF/25V didn’t needed(incase that only one IC).

www.tokopedia.com/madagang .Buy and Donated cheap electronics and manuscripts.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

 

Mithrandir_ wrote:
I tried to add the image but I ran into the not authorized to view this page error. I'll try copy-pasting next time but I am on a Mac/Linux system, I don't have paint.
I'm the one who edited #1 and made the picture visible in the post. My technique for doing that is as follows (using Chrome - no need for a Pain program).

 

So I [ Edit ]  the message:

 

 

then select "Add Attachments" to access the pictures that have already been attached:

 

then I right click the picture of interest and "Open link in new tab":

 

 

Then I right click the image and "Copy Image"

 

 

Then I go back to the message editor, position the cursor and simply Ctrl-V to paste it in the message:

 

 

Simple as that. cheeky

 

EDIT well I was going to edit "Pain" to be "Paint" but I think I'll leave it for now!

Last Edited: Thu. Oct 21, 2021 - 10:45 AM
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Mithrandir_ wrote:
Why do some capacitors have these values while some do not?

 

Without Voltage specification it means: take whichever cap you have- it is presumed to work on 5V.

This is true for 0.1uF, and almost all SMD-caps will work on 5V, up to 10V.

Some really large SMD-caps (22uF or more) may have just 10V max, or less.

 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

You generally see that on electrolytic, or tantalum caps, as it's more critical on these types, but seldom on ceramic caps, although all caps have a voltage spec.

So, no, it's not unusual at all.

 

Jim

 

FF = PI > S.E.T

 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

awneil wrote:

Example:

https://www.circuitlib.com/index...

 

Look at C2,C12 and C14.That similiar with your Elco cap.function.Expecially C2... 

www.tokopedia.com/madagang .Buy and Donated cheap electronics and manuscripts.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Meanwhile the C11 and C13 had similiar function with your 0.1uF IC decoupling.

www.tokopedia.com/madagang .Buy and Donated cheap electronics and manuscripts.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

in that one, none of the capacitors has its voltage shown in the schematic; my point in posting it was to illustrate that some (not all) of the resistors have their power rating - but only in the cases where that is "special".

Top Tips:

  1. How to properly post source code - see: https://www.avrfreaks.net/comment... - also how to properly include images/pictures
  2. "Garbage" characters on a serial terminal are (almost?) invariably due to wrong baud rate - see: https://learn.sparkfun.com/tutorials/serial-communication
  3. Wrong baud rate is usually due to not running at the speed you thought; check by blinking a LED to see if you get the speed you expected
  4. Difference between a crystal, and a crystal oscillatorhttps://www.avrfreaks.net/comment...
  5. When your question is resolved, mark the solution: https://www.avrfreaks.net/comment...
  6. Beginner's "Getting Started" tips: https://www.avrfreaks.net/comment...
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Thank you all for your answers. It is very much appreciated.

 

On a related note, why would you plug two capacitors in parallel with ground such as they have done here? Why wouldn't you just pick a capacitor with whatever capacitance you want, or is there a specific reason for why they suggest this?

1010001010111101110111

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

 

Mithrandir_ wrote:
why would you plug two capacitors in parallel with ground such as they have done here? 

This is standard practice: the electrolytic protects against slower transients; the other one protects against higher frequencies.

 

See: https://techweb.rohm.com/knowled...

 

By adding a capacitor with a small capacitance, the impedance at high frequencies can be lowered. The frequency characteristics of 0.1 μF and 0.01 μF capacitors are combined with the characteristic of a lone 22μF capacitor, resulting in the characteristic shown (broken red line).

 

 

 

Top Tips:

  1. How to properly post source code - see: https://www.avrfreaks.net/comment... - also how to properly include images/pictures
  2. "Garbage" characters on a serial terminal are (almost?) invariably due to wrong baud rate - see: https://learn.sparkfun.com/tutorials/serial-communication
  3. Wrong baud rate is usually due to not running at the speed you thought; check by blinking a LED to see if you get the speed you expected
  4. Difference between a crystal, and a crystal oscillatorhttps://www.avrfreaks.net/comment...
  5. When your question is resolved, mark the solution: https://www.avrfreaks.net/comment...
  6. Beginner's "Getting Started" tips: https://www.avrfreaks.net/comment...
Last Edited: Thu. Oct 21, 2021 - 02:30 PM
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Mithrandir_ wrote:
It's strange that they chose to include it in the circuit, isn't it?

You could argue that it is strange that they specify a voltage for the electrolytic (and 25V is way overkill for a 5V circuit), but they don't specify a voltage for the 0.1.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 1

One important note: keep both caps close together, quality grounding is essential, as always.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 1

You will see on a lot of schematics some notes like:

 

All Resistors are 1/4W,  5% tolerance, unless shown otherwise

All Capacitors are Ceramic 50V, X7R types, unless shown otherwise

Keep your fingers in your nose, away from High Voltages

 

(remember the days when 1% resistors were relatively premium parts?)

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

Last Edited: Fri. Oct 22, 2021 - 07:09 AM
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 1

This. Most generic circuits can/will use generic parts, which should be specified in the drawing as above; specific parts which may be different should be marked on the drawing by the component itself.

 

As an example: my RFID stuff (modified from designs by my ex boss) required some very special capacitors in the RF resonator stage; and in one or two places even a specification was insufficient - to meet radiated noise limits we were in some cases down to a specific manufacturer/package/rating capacitor. But most of the board was 1% 1/8W resistors and 50V ceramic XR7, so nothing on the circuit diagram except a number and a value.

 

Neil

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

avrcandies wrote:

You will see on a lot of schematics some notes like:

 

Keep your fingers in your nose, away from High Voltages

 

 

Never actually seen that on a schematic, but now I'm highly tempted to put it in...  wink  S.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

grohote wrote:

Some really large SMD-caps (22uF or more) may have just 10V max, or less.

the elco cap in 5 Vdc operate only need 10V and in the schematic with 15V,that’s sufficient..

www.tokopedia.com/madagang .Buy and Donated cheap electronics and manuscripts.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

awneil wrote:
This is standard practice: the electrolytic protects against slower transients; the other one protects against higher frequencies.

Only if using through hole capacitors.

 

But if we are using smd components there is no reason to use three different values for decoupling capacitors. Due to their smaller size which means low inductance is same for all small SMD capacitors, then we must use high value capacitors like 22uF or more in smaller size, if more charge is needed put multiple same value SMD capacitors in parallel. 

 

awneil and other members here, I recently found this out. If you watch this 10 minute part of this Eric Bogatin video from altium, your perception might change about the decoupling capacitors. And the myth about using 3 different values for decoupling capacitors.

“Everyone knows that debugging is twice as hard as writing a program in the first place. So if you're as clever as you can be when you write it, how will you ever debug it?” - Brian W. Kernighan
“Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away.” - Antoine de Saint-Exupery

Last Edited: Sun. Oct 24, 2021 - 01:56 PM
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

awneil wrote:

 

Mithrandir_ wrote:
why would you plug two capacitors in parallel with ground such as they have done here? 

This is standard practice: the electrolytic protects against slower transients; the other one protects against higher frequencies.

 

See: https://techweb.rohm.com/knowled...

 

By adding a capacitor with a small capacitance, the impedance at high frequencies can be lowered. The frequency characteristics of 0.1 μF and 0.01 μF capacitors are combined with the characteristic of a lone 22μF capacitor, resulting in the characteristic shown (broken red line).

 

 

 

Fair enough, thank you yet again!

1010001010111101110111

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

awneil and other members here, I recently found this out. If you watch this 10 minute part of this Eric Bogatin video from altium, your perception might change about the decoupling capacitors. And the myth about using 3 different values for decoupling capacitors.

That was a great video, I've seen one of his books before & it was quite informative.  Multilayer ceramic SMD caps are so available these days, its hard to appreciate all the issues with old caps and their inductive leads.   A big drawback for the compact high uf ceramics today, is still their very lousy voltage performance vs uf derating.  But MLCC's just keep improving.  https://blog.knowlescapacitors.c...

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

avrcandies wrote:
A big drawback for the compact high uf ceramics today, is still their very lousy voltage performance vs uf derating.  

Which is, again, where it becomes important to put the voltage spec on the schematic.

Top Tips:

  1. How to properly post source code - see: https://www.avrfreaks.net/comment... - also how to properly include images/pictures
  2. "Garbage" characters on a serial terminal are (almost?) invariably due to wrong baud rate - see: https://learn.sparkfun.com/tutorials/serial-communication
  3. Wrong baud rate is usually due to not running at the speed you thought; check by blinking a LED to see if you get the speed you expected
  4. Difference between a crystal, and a crystal oscillatorhttps://www.avrfreaks.net/comment...
  5. When your question is resolved, mark the solution: https://www.avrfreaks.net/comment...
  6. Beginner's "Getting Started" tips: https://www.avrfreaks.net/comment...
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

awneil wrote:
voltage spec

On smd caps? Do they put any marking? There is no place, and color-coding body is not standardized.

 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

grohote wrote:
Do they put any marking? There is no place

That's a common problem with all SMD components - nothing to do with what you put on the schematic!

Top Tips:

  1. How to properly post source code - see: https://www.avrfreaks.net/comment... - also how to properly include images/pictures
  2. "Garbage" characters on a serial terminal are (almost?) invariably due to wrong baud rate - see: https://learn.sparkfun.com/tutorials/serial-communication
  3. Wrong baud rate is usually due to not running at the speed you thought; check by blinking a LED to see if you get the speed you expected
  4. Difference between a crystal, and a crystal oscillatorhttps://www.avrfreaks.net/comment...
  5. When your question is resolved, mark the solution: https://www.avrfreaks.net/comment...
  6. Beginner's "Getting Started" tips: https://www.avrfreaks.net/comment...
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Yeah, it's bugged me for years that they can mark resistors - at least down to 0603 - but there's *never* a mark on a cap that size. Occasional oddball caps like an 0805 tantalum might have a mark, but that's about it.

 

You want your caps labelled, you better drill some holes!

 

Neil

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

but there's *never* a mark on a cap that size.

Maybe it's hard to fast-mark ceramic (compared to whatever the resistor pkg is)? Or they figure everyone is just using 0.1uF??!!!

Some LEDs are very hard to manually orient (look for the microscopic dot).

I like parts, like SOT-23, that you can't install backwards....not that reversed zeners ever happened crying

 

  

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Heisen wrote:
Only if using through hole capacitors.
Convert your CAD to .brd file.

www.tokopedia.com/madagang .Buy and Donated cheap electronics and manuscripts.