Properties of Capacitors of differing types.
Martin_H
Posts: 4,051
In circuits and electronics they told us that a capacitors are defined by capacitance in farads and breakdown voltage. But in the real world there are many different types of capacitors: ceramic disk, Tantulum, polarized electrolytic, non-polarized electrolytic. I originally thought that the capacitance required dictated the technology used, but I've noticed there is significant overlap between different types.
What I want to know is are capacitors of different types with equivalent measurements electrically identical or not? If they are not, then how do I know what type is needed from a schematic? The reason I am asking is I am fixing a board that looks like it has some bad 1uF 50 volt polarized electrolytic, my local Radio Shack only has Tantulum and non-polarized electrolytic with those specs. Can I substitute?
What I want to know is are capacitors of different types with equivalent measurements electrically identical or not? If they are not, then how do I know what type is needed from a schematic? The reason I am asking is I am fixing a board that looks like it has some bad 1uF 50 volt polarized electrolytic, my local Radio Shack only has Tantulum and non-polarized electrolytic with those specs. Can I substitute?
Comments
You can't directly substitute a polarized electrolytic for a non-polarized one. You can take two polarized ones with double the capacitance and put them back-to-back (positive to positive) in series to substitute for a non-polarized electrolytic.
I don't think it's wise to ever substitute for a non-polarized type, as those are meant for certain specialized applications, such as audio speakers. Keep with polarized if that's what the circuit had or calls for.
You can often replace an aluminum electrolytic with a tantalum cap. Most times people try to avoid it, if possible, as tantalum is generally more expensive. I wouldn't say the reverse is recommended. If a circuit uses a tantalum type, best keep with it.
-- Gordon
Edit: I see Mike beat me to the punch by a few minutes. Go with what he says.
The ESR definitely sounds like one of those things they didn't bother to tell us about in C & E. I guess the EE department shops in the same store where physicists buy massless ropes and pulleys.
Tantalum have much better service life, many aluminium electrolytics are rated at only 2000 hours (3 months!).
The differences between capacitor types are many, and sometimes its really important. There is series resistance, series inductance, aging, ripple-current rating, microphony, non-linearity, dielectric absorption, Q-value, leakage current and temperature coefficient to consider. Many properties depend on frequency too. The only "perfect" dielectric is a vacuum! For high accuracy/stability at low frequencies certain polymer dielectrics like polystyrene do well, for low ESR and ESI ceramics win (but they have poor temperature performance, poor linearity, poor Q, are often microphonic and can age a lot - however this is fine for decoupling.)
The ST232 uses 0u1 and has the same MAX232 pin-out.
http://www.analog.com/library/analogDialogue/Anniversary/21.html
http://en.wikipedia.org/wiki/Types_of_capacitor
http://en.wikipedia.org/wiki/Capacitor
http://www.radio-electronics.com/info/data/capacitor/capacitor_types.php
And here is an excellent test tool for caps and a document that explains how they fail:
http://www.teknetelectronics.com/DataSheet/SENCORE/SENCOLC103.pdf
Sencore also had some awesome PDF's on capacitors and testing but I can't seem to find those at the moment.
http://www.mouser.com/ProductDetail/Yageo/CC1206KKX5R7BB106/?qs=IbgLjqUpHQC9zGzN8Ws9cA%3d%3d
from 11uf-50uF Tantalum Capacitors
http://www.mouser.com/Passive-Components/Capacitors/Tantalum-Capacitors/_/N-75hqvZscv7?P=1z0wq3kZ1z0wqrxZ1z0wkd4Z1z0wq33Z1z0wrjjZ1z0wqqfZ1z0wqsmZ1z0wpztZ1z0wqrdZ1z0wrkiZ1z0wpyeZ1z0wqt0Z1z0wrjiZ1z0wiygZ1z0wqruZ1z0wrkgZ1z0wpzsZ1z0wqr8Z1z0wqslZ1z0wqroZ1z0wjbjZ1z0wq4iZ1z0wrk9Z1z0wrj4&Ns=Pricing|0
50uF+ Aluminum Electrolytic Capacitors:
http://www.mouser.com/Passive-Components/Capacitors/Aluminum-Electrolytic-Capacitors/_/N-75hqtZscv7?P=1z0wqtfZ1z0wl3aZ1z0wqufZ1z0wqqeZ1z0wqdrZ1z0wm3cZ1z0wrjxZ1z0wm2pZ1z0wqspZ1z0wrjuZ1z0wqrrZ1z0wka4Z1z0whjrZ1z0wiyvZ1z0wli4Z1z0wljbZ1z0wrkmZ1z0wmfaZ1z0wrjeZ1z0wrkpZ1z0wmf7Z1z0wqrfZ1z0wqs5Z1z0wrjaZ1z0wm2fZ1z0wrkbZ1z0wqe9Z1z0wm47Z1z0wm4qZ1z0wrk3Z1z0whpvZ1z0wlf6Z1z0wqt2Z1z0wrivZ1z0wmgiZ1z0wrjq&Ns=Pricing|0
http://www.intersil.com/data/an/an1325.pdf
and here:
http://www.electronics-tutorials.ws/capacitor/cap_1.html
A take away from both of these is understanding the effective frequency ranges of different capacitor's types/values.
This is why a parallel combination of a large-ish value electrolytic with a small-ish value ceramic is commonly seen (the the electrolytic deals with signal pertubations below 1MHz, and the ceramic handles the pertubations above 1MHz).
:cool:
I think that is why you'll often see both a larger 10-100uf electrolytic cap and a smaller .1uf cap in Parallel on supply lines in many places.
Robert
I've cleaned it up; the original was too wordy...
The BS2e OEM was damaged, so I will get a BS2SX OEM as an upgrade and my project can continue.
Right On.