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470uF how many volts?
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470uF how many volts?

by tkuhrich on Thu Jul 30, 2020 10:20 pm

I am just starting out programming with an Arduino. I started with a servo and a few LEDs. Some times when my servo starts up, the LEDs will go out. I found the solution over in the Learning area, it says to place a 470uF capacitor between the 5 volt and ground on my breadboard. I have found several 470uFs on ebay but they come in several different flavors. What is the difference between 470uF 25v or 470uF 100v? Is that 50 volts vs 100 volts? If so, do I really need 25 volts?

Thanks,
Kent

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Re: 470uF how many volts?

by westfw on Fri Jul 31, 2020 1:37 am

The voltage rating is the maximum voltage that cap can withstand without being in danger of ... blowing up.
For this arduino purpose, where the voltage is 5V, a cap with at least a 10V rating will give you plenty of safety margin, so 25V is fine, and 100V is definitely overkill. A higher-voltage capacitor is likely to be larger and more expensive (but beware assumptions - 16V is a "standard" voltage, and you might find a wider variety of sizes and prices for 470uF @ 16V than at other voltages.)

Capacitors are one of the things that have a reputation for being counterfeited by dishonest vendors. It's probably not an issue for the size you're looking at, but... http://www.1000uf.com/ipaware/fake-capacitor.html

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Re: 470uF how many volts?

by adafruit_support_mike on Fri Jul 31, 2020 1:59 am

A capacitor's voltage rating tells you the maximum voltage you can have between the plates. Any higher voltage can produce a short circuit between the plates, which can spoil your day:

https://www.youtube.com/watch?v=9jDsNe_bmtE

Dave hooked electrolytic caps up backwards to guarantee a quick failure, but capacitors connected to a voltage that's too high will fail the same way.

As a rule of thumb, you want a capacitor rated for at least twice the maximum voltage you expect it to see. If you're working at 5V, any capacitor rated for 10V or more would be fine. Using 6.3V caps would be risky though.. it's best to assume that any system will have voltage spikes once in a while, and you want the capacitor to handle those as well.

There's no harm in using capacitors rated for a higher voltage than you actually need. They'll be larger than caps with a lower voltage rating:

https://www.digikey.com/product-detail/ ... ND/2796897 - 470uF / 10V (6.3mm x 8mm)
https://www.digikey.com/product-detail/ ... ND/2652041 - 470uF / 25V (8mm x 10.5mm)
https://www.digikey.com/product-detail/ ... -ND/245044 - 470uF / 50V (10mm x 22mm)
https://www.digikey.com/product-detail/ ... -ND/589120 - 470uF / 100V (16mm x 27mm)
https://www.digikey.com/product-detail/ ... ND/2540172 - 470uF / 220V (25mm x 27mm)

but that usually isn't a problem in hobby electronics.

The reason you might want to buy a 100V capacitor for a 5V circuit is price. If there's a lot of demand for a certain combination of values, lots of companies will make them and there will be lots of price competition. Capacitors rated for higher voltages often cost less than caps of the same value rated for lower voltage, simply because the higher voltage is more popular.

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Re: 470uF how many volts?

by westfw on Fri Jul 31, 2020 9:15 pm

It's also an inventory thing. If you buy 6.3V capacitors, you'll only be able to use them on 5V and lower circuits. If you get 25V caps, you'll also be able to use them for filtering on 12V automotive applications, 18V op-amp circuits, etc..

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Re: 470uF how many volts?

by tkuhrich on Sat Aug 01, 2020 11:52 am

Thank you all for your prompt replies. All good information that I need, thank you!

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Please be positive and constructive with your questions and comments.