Elko voltage - Page 1
Forum section: electronics / beginners

author: JanJansen
author_rank: Frequent Contributor
timestamp: June 04, 2017, 04:44:51 pm
content: Hi, what is the best voltage rating on elkos to use ?Here i read normally used around 80% for best life expectancy :http://www.eetimes.com/author.asp?doc_id=1279791Somewhere else i readed that elko lifetime is calculated with 100% voltage at max temprature,they say its best to use a higher voltage rating for best life expectancy.What is realy best ?thanks in advance

author: Rolo
author_rank: Regular Contributor
timestamp: June 04, 2017, 04:55:13 pm
content: For non dutch readers : elko = elco = electrolitic capacitor 😀Verstuurd vanaf mijn ONEPLUS A3003 met Tapatalk

author: MagicSmoker
author_rank: Super Contributor
timestamp: June 04, 2017, 05:04:16 pm
content: While it is generally accepted that derating the voltage applied to an elko will extend its life, there is considerable debate as to how much benefit you get vs. the amount of derating. Lowering temperature (or, somewhat equivalently - reducing ripple current) has a much more dramatic effect, following the Arrhenius equation (approx. x2 change in life for a 10C change in temp).Lifespan flattens out somewhere around 100k hours for most elkos regardless of how much you baby them, so if you need guaranteed performance over a longer span than about 10-15 years then you either need to use a different type of capacitor or make it easy to replace the elkos at prescribed maintenance intervals.

author: tooki
author_rank: Super Contributor
timestamp: June 05, 2017, 03:58:44 am
content: Quote from: Rolo on June 04, 2017, 04:55:13 pmIn German it's Elko, too! (Of course, a hypothetical English "elco" would be short for "electrolyticcondenser". No idea why English switched away from the word "condenser" while every other language kept it...)

author: tooki
author_rank: Super Contributor
timestamp: June 05, 2017, 04:05:52 am
content: Quote from: JanJansen on June 04, 2017, 04:44:51 pmFrom what I've seen, you wanna go higher than the expected voltages. Though apparently for some usage scenarios that rely on the ESR of the cap, you don't want to go insane, either, with either the value or voltage rating. (In many applications, higher value is not a bad thing, but it depends.) Of course, the smallest value electrolytics often don't come in less than 50V. So if you see a schematic specify a 50V electrolytic on a 12V rail, then there's no need to go higher voltage. But for a 12V rail, for example, I wouldn't go below 16V, and 25V would probably be better, especially if the device will get hot.

author: JanJansen
author_rank: Frequent Contributor
timestamp: June 05, 2017, 04:14:05 pm
content: Thank you Tooki,if low value caps are not available in less then 50v it dont matters much i think, else they still made those with a lower voltage rating.I use low ESR elko`s used for general purpose, 5000 - 10000 hours, no special low ESR needed, i just want the longer lifetime.I was planning to make a -15 & +15 volt supply from a 15v AC wall-adapter, something like this :I,m new to this AC adapter stuff, i need the symmetrical power to build a TR808 drummachine clone ( without sequencer with MIDI ) :http://www.dinsync.info/2010/02/roland-tr-808-service-manual.htmlI have a 1A AC wall adapter, i hope its enough for all sounds.I was shopping for C1 and C2, in big values,25v is not enough i think, since the voltage will be 21v coming from those diodes, so i went searching online for some info.( i added 2700 uF at 35v to my cart now to be safe ).For C3 & C4 i plan using 1500uF.

author: Kjelt
author_rank: Super Contributor
timestamp: June 05, 2017, 05:33:55 pm
content: Dont forget the 100nF ceramic capacitors directly (very close) to the input and output of the voltage regulators.

author: rdl
author_rank: Super Contributor
timestamp: June 06, 2017, 12:00:04 am
content: C3, C4, C5, and C6 are probably supposed to be decoupling capacitors 10- to 100 nF ceramic or film type are fine. As said, put them as close as possible to the regulator in and out pins. C7 and C8 are maybe a bit too large, but it depends. You also might want diodes on the output for reverse polarity protection. Electrolytic capacitors with 35 wvdc on the in side will be fine.

author: JanJansen
author_rank: Frequent Contributor
timestamp: June 06, 2017, 01:12:02 pm
content: I,m planning polyester or polypropylene 330n at regulator in, 100n at regulator out, about 5mm distance from the regulator,also a small heatsink on those regulators.Is it is better to place the 5volt regulator on the 15 volt regulator output so it wont heat up to much ?, or would you do the same as those 15v regulators ?

author: Zero999
author_rank: Super Contributor
timestamp: June 06, 2017, 01:46:15 pm
content: How much current does the 5V circuit use?By the way, with this sort of circuit, there's a chance of overheating the transformer if there is a significant imbalance between the current taken from the +V and -V rails. If the 5V load as huge, compared to the +/-15V load, then using this circuit is a bad idea in general.

author: JanJansen
author_rank: Frequent Contributor
timestamp: June 06, 2017, 02:41:48 pm
content: Ok thanks,the +V is always more used then the -V i think.The 5v is for a PIC16 @ 32MHz with a 20mAh LED attatched to chip, also optocoupler and hexinverter for MIDI + R2R opamp & 2x 4051 for velocity.Does the regulator ( = transformer ? ) overheat at what balance ?I care most about noise on the output, if no sound plays, it need to be 100% silent.Aint there a part that uses -15 volt to 5v ?