What is the difference between an electrolytic...

So I am trying to do a project with some capacitors. It isn't that hard of a project but I've never worked with caps before so I thought it would be a nice introduction.

In my region it is fairly hard to get parts for a project. I have a trip to the nearest store (30km) with my parents planned for next weekends to buy parts for this project.

the question: what do I look for when buying caps and does it matter if I buy electrolytic or the brown sort of caps?

This could be a really dumb question... but if I learn something about caps I got all the basic parts of electronics down :)

Yikes, where to begin?

The most important numbers are capacitance and voltage rating. Those are the first things to look for. If a capacitor is going to experience voltages of V volts, you want to pick one with a voltage rating greater than V.

The dielectric choice (electrolytic vs. "brown" which is probably ceramic) determines energy storage density (capacitance vs. volume) as well as how the capacitor behaves with temperature, what its internal resistance is, etc. While electrolytics have the highest energy storage density (most capacitance for a given size) they are the worst type of capacitor in the other respects: their capacitance changes a lot with temperature, they will "dry out" and fail when operated at >85C for long periods of time, they have higher internal resistance, etc.

Wikipedia has a lot more detail on this:

http://en.wikipedia.org/wiki/Capacitor#Capacitor_types

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so basically if I needed a specific electrolytic capacitor for a project I could exchange it for a ceramic one?

Yes, if you needed a 10uF electrolytic you could exchange it for a 10uF ceramic (but watch the voltage rating!) There are a very few situations when the series resistance of electrolytics is actually expected by a circuit (e.g., low-drop-out voltage regulators) but unless you know this to be the case you needn't worry about it.

Another popular choice is tantalum: not as energy-dense as electrolytic but more than ceramic, and better quality than electrolytic. Between those three types they will meet 99.9% of your capacitor needs.

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Normally you can't get high values in ceramic capacitors, all the high values are electrolytic.

There is a cross over region from 1uF to 10uF where you can get both but electrolytics are cheaper.

the shop I am planning to take a trip to has 2 sets of capacitors. One ceramic and one electrolytic. They both are 15 dollars and contain the following:

Ceramic set: 21 x: 10pF, 100pF, 1nF, 10nF, 100nF 14 x: 22pF, 47pF, 220pF, 470pF, 2.2nF, 4.7nF, 22nF, 47nF 7 x: 220nF

Electrolytic set: 15 x - 1µF/50V, - 2.2µF/50V - 4.7µF/50V - 10µF/50V - 22µF/50V - 47µF/25V - 100µF/25V

5 x - 220µF/25V - 470µF/25V - 1000µF/25V

I usually make small things... servos and the like. None of my projects ever exceeded the size of 2 altoids tins. Wich set should I get for simple things like 555 circuits and everything arduino related?

Frankly, I'd get both sets. Have you considered buying online? You can get many more caps for $15 than what your store is offering:

http://elexp.com/cmp_erkt.htm http://elexp.com/cmp_drkt.htm

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Ok, so you would get both sets and then gave me an awesome link about more, cheap caps.

Could you explain to me why I should buy both?

The smaller caps will be useful for filtering, timing, audio work, etc. while the larger caps will be useful for bulk decoupling (smoothing out voltage supplies) also audio work, etc.

And because paying $15 now is going to feel a lot better than travelling 60km later :)

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Okay thank you for your help! May I ask you something as a new member of this forum? Why am I a ‘yaBB newb’ and are you a ‘god member’?

And what does YaBB mean…? :-/

yaBB is (a cheesy) forum software, the titles mean nothing they just go up with the amount of posts you make

I’d bet a lot of money that yaBB stands for “Yet Another Bulletin Board”…

Andrew

I definitely shall not comment on capacitor types - would need too many lines...

15 dollars... I think this a reasonable price, as there are 150 pieces if I have counted correctly, this is 10 cents a piece.... It should be less expensive when you buy exactly what you need, but as most will not be used shortly this is a useless calculation. There had been times when the ratio of used pieces : cheap bought pieces was so bad that I came upto 1$/used piece :-)

The sortiment is well organized, you will rarely need anything outside the E3 values (1, 2.2. 4.7). You will most likely use only a small part of the electrolytes, but I second RuggedCircuit's argument...

it seems that the collections cover most common values, I bought a few “kits” of different values, you will soon find which you use most of and replenish in bigger quantities!

Electrolytics in the range of 1uf = 1000uf are good to go with 555 for flashing circuits, lower values work for sound on 555’s!

depending on what you want I have been using ebay to buy most components from Hong Kong as it works out cheaper, i often end up with 10x as many for the same price as I can buy in the UK!

One thing that hasn't been mentioned is that electrolytics have polarity. You need to get them the right way round. Both your schematic and the caps themselves should be marked.