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i need help with the Easy Adjustable Supply
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i need help with the Easy Adjustable Supply

by matt0514 on Wed Feb 25, 2009 8:23 pm

i thought this was gunna be easy, but im having some troubles with it. first of all, i can't figure out the polarity of the electrolytic caps. i was assuming that white was positive. second of all, the 5k trimpot that i am using, it seems to be going from 1.25V up to 7V quickly (about halfway) and then just staying there at 7V for the turn. also, why does the schematic show a 10uf and a 1uf electrolytic cap. but ladyada says to use 2 x 10uf ? im still an electronics noob . this just doesnt seem 100% clear to me.
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Re: i need help with the Easy Adjustable Supply

by magician13134 on Wed Feb 25, 2009 10:13 pm

The white side is negative. (Shorter leads will, for the most part, always be negative). The pot you are using is probably not linear, you'll just have to tune it very carefully or get a different pot.
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Re: i need help with the Easy Adjustable Supply

by mtbf0 on Wed Feb 25, 2009 10:15 pm

the stripe on the cap is the cathode. there's a little rectangle on it that is supposed to be a minus sign.

sounds like you're using an audio pot. the resistance changes logarithmically, not linearly.
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Re: i need help with the Easy Adjustable Supply

by matt0514 on Wed Feb 25, 2009 11:39 pm

i know how to read the polarity on the actual caps, but i meant on the schematic. there is no plus or minus sybmol. so you say white is negative?
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Re: i need help with the Easy Adjustable Supply

by zener on Wed Feb 25, 2009 11:55 pm

Basically, you have to put the plus end of the cap to the side of the circuit that is more positive. Hopefully that is easy to figure out. You could always check with a volt meter. As long as you don't reverse polarity a polarized cap then it is happy.

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Re: i need help with the Easy Adjustable Supply

by magician13134 on Wed Feb 25, 2009 11:58 pm

Where is the circuit you're looking at? Is it on this site?
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Re: i need help with the Easy Adjustable Supply

by matt0514 on Wed Feb 25, 2009 11:59 pm

http://www.ladyada.net/library/equipt/diypsupp.html

im just used to seeing the + on one side of the cap in the schematic.
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Re: i need help with the Easy Adjustable Supply

by zener on Thu Feb 26, 2009 1:32 am

Shortest answer is : Attach minus side to ground.

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Re: i need help with the Easy Adjustable Supply

by magician13134 on Thu Feb 26, 2009 11:31 am

Oh, sorry. I didn't understand your question until I saw the schematic.
Use this site:
http://www.best-microcontroller-project ... mbols.html
Image

Also, the specific value of the capacitor should not really make a difference, you should be fine with two 10s or one of each.
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