Capacitors in series

[DioniaMuscipula]

I'm working on a Arduino project and I need to place a 111nf capacitor in when I only have ceramic .1mf caps but loads of them.

What I would like to know is how many I would need. I have plenty of breadboard space :]

Andrue

Sent from my F8331 using Tapatalk

Sent from my SM-G903F using Tapatalk

[TimFox]

What tolerance do you need for the 111 nF capacitance, and what is the tolerance of your  100 nF capacitors?
If the 100 nF capacitors are X7R or Z5U (typical dielectrics for bypass use), they will also have large uncertainties due to the voltage co-efficient of capacitance.  100 nF C0G/NP0 capacitors exist, but are somewhat pricey.  Even then, with 5% tolerance, you would need to measure individual units to obtain, say, 1% tolerance on the 111 nF total (+/- 1.1 nF).

[capt bullshot]

Is this capacitor part of a R/C circuit?
Usually one adjusts the value of the resistor to match the capacitor value that is available.

Otherwise, nine 100nF in series give 11nF, place these in parallel to one 100nF results in your desired 111nF 

[Benta]

100 nF in parallel with 10 nF in parallel with 1 nF.

Noone I know would ever do this...

[Zero999]

I'm working on a Arduino project and I need to place a 111nf capacitor in when I only have ceramic .1mf caps but loads of them.

What I would like to know is how many I would need. I have plenty of breadboard space :]

Andrue

Sent from my F8331 using Tapatalk

Sent from my SM-G903F using Tapatalk

Strictly speaking 1mF is 1000µF, so 0.1mF is 100µF.

In reality, the lower case "m" used to be used, as short hand for micro, so .1mF is an archaic way of writing 100nF, 100 000pF or 0.1µF.

To get 111nF from 100nF capacitors is not practical, because, as mentioned above, it would require ten capacitors: one 100nF capacitor, in parallel with nine 100nF capacitors connected in series. In reality it's likely the tolerance of a single capacitor would be around 10%, meaning its actual value could range from 100nF - 10% = 90nF, to 100nF + 10% = 110nF, so aiming for 111nF is pointless.

[Brumby]

That is a rather curious value to aim for and with tolerances, it will be a fluke if you got within +/- 1 of your 111 target.  If you had a capacitance meter, you might be able to close in on that value by trying the above combinations from your pool of capacitors.

It is not common for someone to aim for such unusual values, especially to the implied accuracy (you want 111nF - not 110nF or 112nF, yes?) - and the question arises: Why do you need to?  In general use, capacitors are rarely expected to be that accurate and designs most often treat their specification as "nominal".

This makes us curious as to why you are seeking this value, as there may be better ways to achieve what you are trying to do.  If you can show us a circuit diagram, or at least describe your circuit and objective, we could make more informed comment.

[DioniaMuscipula]

Hello everyone and thanks for the feedback

Here is a link to the project.

https://www.arduino.cc/en/Tutorial/SimpleAudioFrequencyMeter

I'm not fussed about the libraries as all I need is the analogue input so that I can translate the frequency range to MIDI. I am using a signal frequency generator.

I notice that 100nf is what is needed. I have a big collection of capacitors; electrolytic, green, red, ceramic but I don't know how to figure the ratings.

Also in the diagram it seems to me that both sides of the capacitor are positive so which way round does it go?

TIA

Andrue

Sent from my F8331 using Tapatalk

[Brumby]

That's a DC blocking capacitor.  It's value isn't all that critical and its voltage rating won't need to be much at all.  Any ceramic cap will be more than enough.

The 100nF capacitors I've seen are not polarised - which means it doesn't matter which way you put them into the circuit.

[capt bullshot]

I notice that 100nf is what is needed. I have a big collection of capacitors; electrolytic, green, red, ceramic but I don't know how to figure the ratings.

The ceramic ones often are marked with a 3 digit sequence of numbers: 104 would be 100nF
(first two digits: value in pF, last digit: add so many zeros, so 10 and 0000 (four zeros) makes 100000pF which equals 100nF)
Electrolytics usually are > 1uF and polarized, the ceramic are not polarized, so doesn't matter which way you put them in.

[DioniaMuscipula]

I'm working on a Arduino project and I need to place a 111nf capacitor in when I only have ceramic .1mf caps but loads of them.

What I would like to know is how many I would need. I have plenty of breadboard space :]

Andrue

Sent from my F8331 using Tapatalk

Sent from my SM-G903F using Tapatalk

Strictly speaking 1mF is 1000µF, so 0.1mF is 100µF.

In reality, the lower case "m" used to be used, as short hand for micro, so .1mF is an archaic way of writing 100nF, 100 000pF or 0.1µF.

To get 111nF from 100nF capacitors is not practical, because, as mentioned above, it would require ten capacitors: one 100nF capacitor, in parallel with nine 100nF capacitors connected in series. In reality it's likely the tolerance of a single capacitor would be around 10%, meaning its actual value could range from 100nF - 10% = 90nF, to 100nF + 10% = 110nF, so aiming for 111nF is pointless.

Thank you, that does make sense. I have point 1mf caps so that is fine. The results I get from the analogue pin are not very diverse. In fact there is not much of a range from say 100hz to 60000hz. The values I get although not random generally stick to a three figure value from about 300 to 600.

Nevertheless if the offset of the tone generator is set below a point the pin returns 0 which can only mean something is working.

It would be nice to have a wider input range.

Andrue

Sent from my F8331 using Tapatalk

[DioniaMuscipula]

I notice that 100nf is what is needed. I have a big collection of capacitors; electrolytic, green, red, ceramic but I don't know how to figure the ratings.

The ceramic ones often are marked with a 3 digit sequence of numbers: 104 would be 100nF
(first two digits: value in pF, last digit: add so many zeros, so 10 and 0000 (four zeros) makes 100000pF which equals 100nF)
Electrolytics usually are > 1uF and polarized, the ceramic are not polarized, so doesn't matter which way you put them in.

That makes sense thank you.

Andrue

Sent from my F8331 using Tapatalk

[DioniaMuscipula]

OK I have a brown set of caps that are not polarised. One says 104j which is I assume 10pf padded left with 4 zeros. But what does the j mean? It also says 400v, what kind of application would high voltage caps be used?

Now another cache of resistors are large and white and have 10W10ohmJ I think Amazon referred to them as super capacitors. Hey I can post images.

The green film caps aren't distinct enough to photograph but I can read them 2A104J. Again don't know what the J is but I'm assuming 2A is amps yes?

Then these purple variable caps that have no marks on them.

I await in anticipation.

Andrue

Sent from my F8331 using Tapatalk

[capt bullshot]

You can look up the meaning of these codes e.g. here:

http://www.robotoid.com/appnotes/electronics-capacitor-markings.html

This states "J" is the code for 5% tolerance (deviation of the actual capacitor value from the nominal).
Your bag states 100pF, thats not 100nF. For a 100pF you'll often find quite high voltage rating, that's just because they can, not because the application requires this.
The "A" in "2A104J" has nothing to do with current or Ampere, but I don't know either what's the meaning. You may try to google this.
The resistors are 10 Ohm, and 10W power dissipation, not super capacitors at all.
For the variable caps the body color often indicates the nomimal value, try to look up at mouser.com or similar.

[ArdWar]

Polyester caps usually marked using EIA code. XXYYYZ where XX is voltage code, YYY is capacitance code, and Z is tolerance code.

2A is code for 100V rating.