Home     Contact     Forum     Projects     Experiments     Circuits     Theory     BLOG     PIC Tutorials     Time for Science     RSS     Terms of services     Privacy policy  
   
 Home     Forum     Projects     Experiments     Circuits     Theory     BLOG     PIC Tutorials     Time for Science   

Author Topic: Led s connected directly to 240V  (Read 5863 times)

0 Members and 1 Guest are viewing this topic.

Andre

  • Guest
Led s connected directly to 240V
« on: March 03, 2008, 12:50:01 PM »
Is it possible to connect leds to 240 v directly (of course with resistors)
Will this be a problem? Can i try it?

I have some hundreds high brightness leds that i want to make a wooden board for top of my house and put them inside random. Do i need transformer or can i connect them directly to 240?

kam

  • Administrator
  • Hero Member
  • *****
  • Posts: 1849
Re: Led s connected directly to 240V
« Reply #1 on: March 03, 2008, 13:56:46 PM »
I have not test it really but this i can tell you. You must for better results have a bridge rectifier that will rectify both negative and positive periods. Also, you will need a resistor to limit current. And then, you will need to make groups of leds in series. What i mean is that each led has a drop of approximately 3 volts (for the hight brightness or different for yours, please measure it). So divide 240 by 3 you get 80. This means that you must have at least 80 leds in series for safe connection to 240V. Then, if you need more leds, you must make another 80-series leds and all these connect in paralel.

The resistor must be connected to each 80-series of leds and must have a value to limit the current to whatever current needs one led. If your leds have enough brightness @ 150mA, your resistor must be

R=U/I => R=240/(150*10^-3) => R=1.6 K
Use dr Calculus for easier calculations

But is you use a good 240/24 transformer, you will need less leds for each group and it will be muvh muvh safer and controlable as you will be able to switch on and off different led groups.
You decide.

Andre

  • Guest
Re: Led s connected directly to 240V
« Reply #2 on: March 04, 2008, 19:19:31 PM »
I get what you mean. I will need to have a transformer after all and for safety reasons.

ScubaCap

  • Guest
Re: Led s connected directly to 240V
« Reply #3 on: March 04, 2008, 22:14:33 PM »
Safety first  ;D

Mosquito

  • Guest
Re: Led s connected directly to 240V
« Reply #4 on: March 15, 2008, 00:14:02 AM »
Also a 1/1 transformer (eg. 110 in 110 out) is for safety because even if you touch one side of the 110 output you gen no electrocution as you close no circuit with earth.

manley_V

  • Guest
Re: Led s connected directly to 240V
« Reply #5 on: March 17, 2008, 23:52:59 PM »
Yes but ONLY if you touch one side  :)
Just for those who do not know

and kids, do not try this at home  ;)