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-   -   DIY AC to DC power converter? (http://www.diychatroom.com/f18/diy-ac-dc-power-converter-57322/)

hefty 11-16-2009 03:38 PM

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.

Yoyizit 11-16-2009 04:04 PM

Quote:

Originally Posted by hefty (Post 353879)
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?

hefty 11-16-2009 04:09 PM

A bunch of 1/2W's...maybe 100Watts altogether

Yoyizit 11-16-2009 04:47 PM

Quote:

Originally Posted by hefty (Post 353896)
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.

hefty 11-16-2009 05:06 PM

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.

jerryh3 11-16-2009 05:12 PM

Quote:

Originally Posted by hefty (Post 353932)
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.

Yoyizit 11-16-2009 05:34 PM

Quote:

Originally Posted by hefty (Post 353932)
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.

hefty 11-16-2009 05:57 PM

Quote:

Originally Posted by Yoyizit (Post 353944)
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. :yes:
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..

Billy_Bob 11-16-2009 07:17 PM

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...

http://www.cnccookbook.com/img/Lathe...ySchematic.jpg

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

Yoyizit 11-16-2009 08:20 PM

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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