80 Leds For Led Light. Can I Run To 230v Mains - Electrical - DIY Chatroom Home Improvement Forum

 DIY Chatroom Home Improvement Forum 80 leds for led light. can i run to 230v mains
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12-25-2007, 08:14 PM   #1
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## 80 leds for led light. can i run to 230v mains

Hi, Im trying to make my own lighting for a small room in my house..
I have 100 led's 18,000mcd, 3.o-3.8 vf,10mm.

Im not sure on how I should calcualte what resistor i need.
I was thinking as they are 3v forwards current, If I use 80 in sequence that would allow me to run it strain off mains current as 3*80 = 240.

I have the leds all mounted and wired on a board with no plug, in seequence but just wanted some help before I plug it in as i dont want to blow them all out..

Can anyone help. thanks

12-25-2007, 09:40 PM   #2
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I have good luck with this site calculating LED resistors.
Scroll down to the calculator.

 12-25-2007, 09:41 PM #3 Newbie   Join Date: Mar 2005 Posts: 12 Rewards Points: 10 oops--forgot the link http://www.bcae1.com/led.htm

 12-26-2007, 01:24 PM #5 Member   Join Date: Aug 2006 Posts: 190 Rewards Points: 150 Don't you need DC voltage for the LEDs? Last I checked, AC didn't work.
12-26-2007, 01:56 PM   #6
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Quote:
 Originally Posted by scorrpio Don't you need DC voltage for the LEDs? Last I checked, AC didn't work.
LED = light emitting Diode

The diode will glow when the AC voltage causes the appropriate forward voltage drop across the diode.

A problem with using AC is that the diode will glow brighter as the AC voltage rises and essentially won't glow at all until the voltage rises above the point that significant current flows through the diode. Of course the LED also won't glow when it is reverse biased.

Last edited by davefoc; 12-26-2007 at 02:22 PM.

 12-27-2007, 05:28 PM #7 Newbie   Join Date: Dec 2007 Posts: 3 Rewards Points: 10 Wouldnt the OP be better off rectifing the AC for more efficient and higher light output? A simple full wave bridge and properly sized capacitor and resistor? http://hyperphysics.phy-astr.gsu.edu...ic/rectbr.html Last edited by AdamVocks; 12-27-2007 at 05:30 PM. Reason: Screwed up the link...
 12-27-2007, 06:05 PM #8 Member   Join Date: Dec 2007 Location: Orange County, California Posts: 34 Rewards Points: 25 The diodes themselves can be used as rectifiers so it might be reasonable to run this off of AC. A capacitor could be added that would extend the time when current was flowing thereby increasing brightness without increasing peak current. Whatever scheme is used that involves a current limiting resistor will have similar losses that will limit efficiency. In looking around on the web a bit I saw a scheme that involved using a series capacitor to limit current. That would probably be more efficient but there are issues that need to be considered before a scheme like that is used.
12-27-2007, 06:23 PM   #9
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Quote:
 Originally Posted by donnol1983 Hi, Im trying to make my own lighting for a small room in my house.. I have 100 led's 18,000mcd, 3.o-3.8 vf,10mm. Im not sure on how I should calcualte what resistor i need. I was thinking as they are 3v forwards current, If I use 80 in sequence that would allow me to run it strain off mains current as 3*80 = 240. I have the leds all mounted and wired on a board with no plug, in seequence but just wanted some help before I plug it in as i dont want to blow them all out.. Can anyone help. thanks

Okay, thanks for all the help.
I think Im going to try to use DC current if the same rules apply then I'll be using around 70led's I'll have to buy a resistor and power convertor but at least I didnt wire the Plug up yet so should have no problem fitting all the things I need in the circuit..
I'll post some pics when I have the light up and running, ma take a few weeks. thanks again guys.

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