ac coupling

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Analog_Fan

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project 213 VCA Ac coupling.jpeg

for the first time, after months i got a error message, capacitor reverse voltage ..., witch seems logical, as it's coupled to a active voltage divider, charging from the negative side.
I need a non polarized.

At first i went mouser to check for Wima 10uF, but the thing is 16 mm high and 11 mm width (MKS), it doesn't fit between stacked PCB's, max 10 mm, unless i paste it on the back, looks a bit unfinished.

i turned on the my scope and synthesizer, my VCO is Make Noise STO, i just found out my VCO can output 25.5 kHz.
I did several test, using Wima's: 47nF, 100nF, 330nF, 1uF and 2 electrolytic 4uF and 10uF.
(a 3.5 m socket for the patch cable with wires soldered on the breadboard).

they are all pretty much suitable so far i could see, the vco (Buchla 259 based) in the high end seems to loose a bit of amplitude.

the line audio input module i made (some years ago), i toke from Befaco inamp uses a 56pF, now they use 47nF.

Most of the time, in many schematics they use either electrolytic 10uF or 4uF7.

I think, i will opt for Wima 1uF.
Now i have been buying all these values, 220nF, 470nF, but looks like unnecessary and could settle for just one (1uF).

What's your thoughts?
 

Analog_Fan

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You can use bipolar or nonpolarized electrolytics, something like the green Nichicon Muse series.
nonpolarized electrolytics, i heard of it, but not giving a though about it.

https://www.nichicon.co.jp › english › index.html

Nichicon Corporation | Home

NICHICON Develops UBH Series of Aluminum Electrolytic Capacitors Guaranteed for 2,000 Hours at 150℃ Oct.19.2020 NICHICON Expands the SLB Series of Small Li-Ion Rechargeable Batteries (High-Rate Charge/Discharge Performance, Long Life, Low-Temperature Capabilities, and Safety) to Include φ8 and φ12.5 Size Versions Oct.15.2020

japan sounds good and mouser has them.


Series: UVP
datasheet

but tolerance 20%

this one could replace the wima's for ac coupling in all situations?
then i skipp the 470n'sF and 220nF's from the order?

that's even cheaper than wima.
 
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Dualflip

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nonpolarized electrolytics, i heard of it, but not giving a though about it.

https://www.nichicon.co.jp › english › index.html

Nichicon Corporation | Home

NICHICON Develops UBH Series of Aluminum Electrolytic Capacitors Guaranteed for 2,000 Hours at 150℃ Oct.19.2020 NICHICON Expands the SLB Series of Small Li-Ion Rechargeable Batteries (High-Rate Charge/Discharge Performance, Long Life, Low-Temperature Capabilities, and Safety) to Include φ8 and φ12.5 Size Versions Oct.15.2020

japan sounds good and mouser has them.


Series: UVP
datasheet

but tolerance 20%

this one could replace the wima's for ac coupling in all situations?
then i skipp the 470n'sF and 220nF's from the order?

that's even cheaper than wima.
Why do you care about the tolerance, as long as it has enough capacitance who cares? you are not using it as a filter or something which needs precision.

Also, you must be doing something wrong, a regular capacitor should be ok, the 100k -100k voltage divider provides 2.5 DC volts at the positive side of the cap, lower because of the reflected resistor of the transistor to te base, but then you have a 1 to 0.01 voltage divider at the input, the label says that the input should be 1V RMS, which means that you have a peak voltage of around 14.14mV at the negative side of the cap, this is far from reversing the polarity. You are doing something wrong, or your simulator is faulty.
 
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abbey road d enfer

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What's your thoughts?
You can't compare a 47nF with a 10 uF.
I have the feeling you don't understand the priorities in selecting a capacitor.
The dominant parameter is capacitance. The value of a capacitor is determined by its position within the surrounding elements, mainly the resistors in coupling and bypass positions.
If you need 10nF, you can't choose an electrolytic (doesn't exist), if you need stability, you can't choose ceramic (except COG/NP0).
If you need 100uF, you must use an electrolytic, then the option polarized/non polar will be oriented by other considerations.
 
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Analog_Fan

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Why do you care about the tolerance, as long as it has enough capacitance who cares? you are not using it as a filter or something which needs precision.

Also, you must be doing something wrong, a regular capacitor should be ok, the 100k -100k voltage divider provides 2.5 DC volts at the positive side of the cap, lower because of the reflected resistor of the transistor to te base, but then you have a 1 to 0.01 voltage divider at the input, the label says that the input should be 1V RMS, which means that you have a peak voltage of around 14.14mV at the negative side of the cap, this is far from reversing the polarity. You are doing something wrong, or your simulator is faulty.
well i have the capacitor in reverse in contrary to this schematic, i consider the "audio" input as the positive side, like i always do.

i use 100K to 504R, instead of 100k to 1k.
 

Dualflip

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well i have the capacitor in reverse in contrary to this schematic, i consider the "audio" input as the positive side, like i always do.

i use 100K to 504R, instead of 100k to 1k.
That is wrong, the positive side should be towards the more positive voltage, the correct orientation is like it is shown in the schematic.
 
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Analog_Fan

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You can't compare a 47nF with a 10 uF.
I have the feeling you don't understand the priorities in selecting a capacitor.
The dominant parameter is capacitance. The value of a capacitor is determined by its position within the surrounding elements, mainly the resistors in coupling and bypass positions.
If you need 10nF, you can't choose an electrolytic (doesn't exist), if you need stability, you can't choose ceramic (except COG/NP0).
If you need 100uF, you must use an electrolytic, then the option polarized/non polar will be oriented by other considerations.
well, using the scope i don't see any or much difference, the signal stayed the same, pretty much.

the VCO on one side of the capacitor and the scope on the other.
i played with lowest frequencies as well the highest.

i used to cursor of the scope, what came in also came out, not drop in amplitude. ... using a sine wave.
but when i changed the shape of the sine wave (a option of the Make Noise STO), i noticed that after the wave has been sliced, it did loose a bit when it return to it's max amplitude.

I'm aware that capacitors used in other situations serve other purposes and needs.
 
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abbey road d enfer

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well, using the scope i don't see any or much difference, the signal stayed the same, pretty much.
That's because the load offered by the oscilloscope is very high, but you must read about RC circuits and impedance. That's the basics of electronics. If you don't understand that, you can't make progress.
 

Analog_Fan

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i wish, i knew how he got that sub oscillator at 0.50 minutes and the overall shape of it.
shifting the "gnd" level.
: )
 
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Analog_Fan

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Didn't you say you were an EE? In any case, check out the book recommendation thread at the top of the Drawing Board forum
that was the origin, but the labor live was different.
it's a replace the broken thing and proceed society o need to investigate why and/or fix it.
 

Analog_Fan

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If they are electrolytic capacitors, they will probably work with reverse voltage for some amount of time, but the oxide will eventually dissolve back into the electrolyte and the device will act as a resistor instead of a capacitor.
i'll opt for the bi-polar electrolytic capacitors mentioned by John12AX7 in this case.
Just to be sure.
 
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