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Old 11-16-2009, 03:38 PM   #1
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DIY AC to DC power converter?


I'm not sure if this is the right place for this or not, but if not maybe someone could point me in the right direction.

I'm trying to design an AC to DC power converter, which I would then like to be able to use to power an LED circuit. Any help would be appreciated. Thanks.

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Old 11-16-2009, 04:04 PM   #2
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DIY AC to DC power converter?


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Originally Posted by hefty View Post
I'm trying to design an AC to DC power converter, which I would then like to be able to use to power an LED circuit. Any help would be appreciated. Thanks.
What LEDs you want to use, and how many?

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Old 11-16-2009, 04:09 PM   #3
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DIY AC to DC power converter?


A bunch of 1/2W's...maybe 100Watts altogether
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Old 11-16-2009, 04:47 PM   #4
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DIY AC to DC power converter?


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A bunch of 1/2W's...maybe 100Watts altogether
200 ea. of 3v LEDs = 600 vdc.
Peak 120vac value is 170v.
170v/3v = 56 LEDs in each string with no allowance for the LM317 set up as a constant current regulator.
0.5w/3v = 170 mA in each string.
So far, so good?
Do you need uniform brightness for the LEDs?
Do you mind if they flicker at 60 or 120 Hz?

Google
boncuk electro
and ask him about LED strings.
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Old 11-16-2009, 05:06 PM   #5
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DIY AC to DC power converter?


Nah...I've done some stuff with LED's before, I'll figure all of that out when I get to it, what I'm trying to do here is get some help with

AC to DC power conversion.
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Old 11-16-2009, 05:12 PM   #6
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DIY AC to DC power converter?


Quote:
Originally Posted by hefty View Post
Nah...I've done some stuff with LED's before, I'll figure all of that out when I get to it, what I'm trying to do here is get some help with

AC to DC power conversion.
Here...
http://cgi.ebay.com/MW-HD-VARIABLE-L...item2ea63c23e3
It's already designed for you.
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Old 11-16-2009, 05:34 PM   #7
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DIY AC to DC power converter?


Quote:
Originally Posted by hefty View Post
Nah...I've done some stuff with LED's before, I'll figure all of that out when I get to it, what I'm trying to do here is get some help with

AC to DC power conversion.
You probably want a constant-current-source/LED driver. With constant voltage sources the LED voltage varies so much that the current is unpredictable. You could use resistors to approximate constant current but that wastes a lot of power.
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Old 11-16-2009, 05:57 PM   #8
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DIY AC to DC power converter?


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Originally Posted by Yoyizit View Post
You probably want a constant-current-source/LED driver. With constant voltage sources the LED voltage varies so much that the current is unpredictable. You could use resistors to approximate constant current but that wastes a lot of power.
Yeah. I like the sound of that.
How does that work?

I saw one guy who was using I think a USB to power his circuit....That might be interesting.

I'm working on designing a PCB to place the diodes on and also to help with heat dissipation, and then from there I guess I'll need to find the right connectors & so on..

Last edited by hefty; 11-16-2009 at 06:12 PM.
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Old 11-16-2009, 07:17 PM   #9
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DIY AC to DC power converter?


Basically you need a step down transformer to the voltage you want, then a "bridge rectifier" which makes "bumpy" DC, then an electrolytic capacitor to "smooth out" the bumps.

This would be a simple "DC power supply".

Like this...



This explains it a bit...
http://www.hardwaresecrets.com/article/327

More...
http://www.google.com/search?hl=en&u...-8&sa=N&tab=iw
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Old 11-16-2009, 08:20 PM   #10
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DIY AC to DC power converter?


http://en.wikipedia.org/wiki/Current_source

I don't know how much power a USB interface can source but almost certainly it is a voltage source.

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