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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
Newbie Component Question
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TronTron



Joined: Aug 27, 2013
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PostPosted: Tue Aug 27, 2013 9:38 am    Post subject: Newbie Component Question
Subject description: Synth-DIY Experimenter Board Component Question
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I have built several kits, but I am a newbie at buying my own components. I am currently working on the Synth-DIY Experimenter Board. My question is:

Does voltage matter when purchasing either capacitors or potentiometers?


thanks,
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PHOBoS



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PostPosted: Tue Aug 27, 2013 1:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

welcome party!

for capacitors yes. They need to be rated for at least the voltage it's used for. I myself usually make sure they can withstand the supply voltage,
but this isn't always necessary because the voltage across the capacitor might be a lot smaller. I also make sure there is some 'reserve', so don't
use 16V capacitors on a 15V supply, but use at least 25V instead. (for +/- 15v dual supply I use at least 35V, just in case)

I do remember reading somewhere that using a capacitor rated for a voltage that is much higher then what it's used for isn't ideal. But I'm
not sure why and haven't had any problems with it. maybe someone else can elaborate on that.


potentiometers usually don't have a voltage rating but a maximum power (wattage) rating. This is dependent on the voltage across the potentiometer
and it's resistance. Standard pots should be fine unless it is mentioned. The same goes for resistors: 1/4 watt is standard unless mentioned.

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analog_backlash



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PostPosted: Tue Aug 27, 2013 3:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi TronTron and welcome.

PHOBoS wrote:
I do remember reading somewhere that using a capacitor rated for a voltage that is much higher then what it's used for isn't ideal. But I'm not sure why and haven't had any problems with it. maybe someone else can elaborate on that.

I too have read this and I have a vague recollection that it said that for electrolytics at least, once you have underrated a capacitor for some length of time, then it will no longer work at its marked working voltage. This is only going to cause a problem if you are going to re-use the capacitor - unlikely once soldered into a PCB, but it might lead to problems if you've breadboarded it.

Gary
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Blue Hell
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PostPosted: Tue Aug 27, 2013 4:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

PHOBoS wrote:
potentiometers usually don't have a voltage rating but a maximum power (wattage) rating. This is dependent on the voltage across the potentiometer and it's resistance. Standard pots should be fine unless it is mentioned. The same goes for resistors: 1/4 watt is standard unless mentioned.


In the complete specs you'll actually find a voltage limit as well, but it's of no consequence practically. The levels usually are a couple of hundreds of Volts, and it's got more to do with electron creep and sparking than with thermal overload ... apart from that with 'normal' valued components you'd usually run into the max dissipation limit before running into the max. voltage limit.

Something to keep in mind tho for your tube projects, just like you should spend some thought then on trace distance, for instance.

I did not know BTW that electrolytes should not be used with too high a working voltage spec .. but indeed they do get 'lazy' (as in they get leaky and their capacitance drops) ... but they can be reconditioned by applying more voltage .. or so I always thought.

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TronTron



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PostPosted: Tue Aug 27, 2013 7:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

thanks everyone!

I did some more reading and now understand about the +/- 12V supply in this project. So in this case, at minimum a ~30V+ capacitor should be used.


As per the potentiometers, if 1/4 Watt is standard, is it OK to use a 1/2 Watt instead? Is going higher an issue?
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elmegil



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PostPosted: Tue Aug 27, 2013 9:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

I would imagine that a 1/2W pot would be much larger than it's 1/4W cousin, and therefore could cause you panel population problems.
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TronTron



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PostPosted: Wed Aug 28, 2013 8:15 pm    Post subject: Re: Newbie Component Question
Subject description: Synth-DIY Experimenter Board Component Question
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Thanks everyone.

What tolerance of capacitors should I look for?
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