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Small ceramic caps are nasty because their markings, such as ceramic monolithic leaded "104M"(yellow-brownish) and epoxy ceramic monolithic leaded "223", do not reveal max values. Since I do not know their manufacturers, I cannot google for their max voltages or max currents.

  1. What is a typical maximum I for the smallcap?
  2. What is a typical maximum V for the smallcap?
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3 Answers 3

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ceramic through-hole caps are usually rather high in voltage rating, i don't think i've seen one in person under 25V except maybe those with high capacitance, >=1uF and they are usually 16V although i know some with smaller voltage ratings are available.

A simple subjective measure is size. For a given capacitance and type of construction (ceramic in this case) the smaller the package the lower the voltage rating.

This rule also means that if you can find a comparable part on digikey to what you have in hand, the voltage rating is probably the same, there aren't too many manufacturers tricks left in the bag when it comes to through-hole ceramics. Of course the only way to be sure is to try it.

As for current. Ceramic capacitors are rarely, if ever, specified with a maximum current. If the current flowing through the cap is large enough to matter your problem will most likely be the impact of the series resistance of the cap on your circuit or it generating enough heat to push the cap outside its thermal limits.

If you need assorted capacitors for your lab i'd look at the cap kits on digikey, there are a bunch of them and they usually come in little "fishing box" like containers that keep them all sorted for you. You also gain the advantage of knowing who made the caps and get actual specs which isn't true of the assortment packs at places like radioshack. You could also get one of those slide bin storage things from a hardware store and make your own capacitor assortment.

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This is actually completely based on manufacturer. I hope someone corrects me if I am wrong, but just for the parts store I help keep stocked at my school we have very similar devices with maximum of 5, 15, and 50V. There is no way to know, but you will probably be fine under 5V.

Sorry, but I do not believe there is a simple answer.

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    \$\begingroup\$ I think the only way you could test the voltage rating of a capacitor is by destroying it. \$\endgroup\$
    – endolith
    Jun 10, 2010 at 4:45
  • \$\begingroup\$ If you set a low current limit and slowly step the voltage up you might be able to figure it out without damaging it. But there is still a 95% chance you will with nice equipment. \$\endgroup\$
    – Kortuk
    Jun 10, 2010 at 15:23
  • \$\begingroup\$ This is not a case of not buying assorted sets, it is a case that you need to keep things organized and labeled. if you could tell everything by just looking at components there would not need to be nearly as strict of design flows as there are. \$\endgroup\$
    – Kortuk
    Jun 10, 2010 at 15:23
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    \$\begingroup\$ @Kortuk: even if you brought the voltage up slowly, the moment the dielectric failed, all the energy stored in the cap at the point of breakdown will dump through the defect. it seems like it will look fine right up to the nanosecond when it pops. \$\endgroup\$
    – JustJeff
    Jun 12, 2010 at 1:23
  • \$\begingroup\$ In my mind i was being hopeful he had a way, I did not think he did, and you confirmed it. \$\endgroup\$
    – Kortuk
    Jun 12, 2010 at 14:13
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All of my personal small caps in Futurlec's value packs are well-labelled between 50V-onwards, btw very price-worthy sets for beginners. The lowest is 1pF with 50V max. My scbool has unlabelled small caps. My teacher said that you can safely test the caps until 5V and even higher because, according to him, ceramic caps do not explode rather burn slowly.

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  • \$\begingroup\$ not trying to pitch digikey specifically, insert whatever distributer you want (mouser, newark, allied). Considering the nature of his question the last thing i would recommend is going and buying another freezer bag of unspecified parts. The bag of ceramic discs on the site you linked only specifies "at least 50v" and if the image is correct, provides no information as to the tolerance, temperature range, ESR or even what values are included in the kit. You get what you pay for. \$\endgroup\$
    – Mark
    Jun 10, 2010 at 20:56
  • \$\begingroup\$ This should have been a comment, and i agree with mark here, he was not pitching digikey. \$\endgroup\$
    – Kortuk
    Jun 11, 2010 at 13:02
  • \$\begingroup\$ checked them well-labelled. Corrected reply to more attacking the question. Thanks for critical feedback. \$\endgroup\$
    – hhh
    Jun 11, 2010 at 22:43
  • \$\begingroup\$ just use your schools caps and if they pop, so what, clearly they were free caps. \$\endgroup\$
    – Kortuk
    Jun 11, 2010 at 22:56

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