LED on 220 VDC

[Sinisa]

Hi!
I am new on this forum, and I think is great. I have a little problem, and I need a some solution, if is possible.
How to connect LED to 220 VDC supply without any transformer. I want to use only resistor because place is very restricted. I belive that is possible, but I don't know value of resistor. Please help me.

 

[Spark123]

220v DC? You don't really want to connect a transformer to DC as it will blow it!! You need to know what voltage and current the LED needs to operate first and then calculate the volt drop at that current for a resistor in series R=V/I, i.e. if the LED is 20mA 2v you need to drop 218v @ 20mA which is 218/0.020=10900ohms. So I would go for a 12K ohm resistor in this instance.

 

[Sinisa]

I am sorry, I make a mistake. I want to connect on 220 VAC.

 

[Spark123]

Will the LED operate on AC? Some LEDs will burn up if connected backwards (or on the negative part of the cycle).

 

[Sinisa]

So, you think that I have to fit rectifier before LED and resistor? I think I can fit that. Thank you for your advise

 

[simon_d]

Will the LED operate on AC? Some LEDs will burn up if connected backwards (or on the negative part of the cycle).

1 diode will protect the LED. but you need 4 (as a rectifier) for better results

basically, you can do it with a diode and resistor and thats it

 

[Sinisa]

OK!!!!
So, rectifire, resistor of cca 12K, and LED.
Thank you all!

 

[simon_d]

OK!!!!
So, rectifire, resistor of cca 12K, and LED.
Thank you all!

but just remember this is NOT isolated from the mains, is not low voltage and must be fully insulated

 

[Adam_151]

I'd advise against a resister in this situation, it'll be sweating off nearly 4w, which as well as requireing a part capable of dispating such a power without burning up, will be terribly inefficent, 99% of the energy is going into warming the resister. A capacitor would probably be a better choice, you are looking at around 220nF at 60hz and 250nF at 50hz

 

[Sinisa]

I'd advise against a resister in this situation, it'll be sweating off nearly 4w, which as well as requireing a part capable of dispating such a power without burning up, will be terribly inefficent, 99% of the energy is going into warming the resister. A capacitor would probably be a better choice, you are looking at around 220nF at 60hz and 250nF at 50hz

Adam, in what way I have to connect this capacitor. in this case I don't need a resistor?

 

[Adam_151]

Adam, in what way I have to connect this capacitor. in this case I don't need a resistor?

In series with the LED, in the same way as the resister was, and yes you are correct the capacitor replaces the resister as the voltage dropping element, but it is adviseable to put something like a 220 ohm half watt resister in series with it as well to limit transisant currents

Ideally you are looking at something along the lines of this (but with the cap values I gave, or rather a *tad* smaller than the ones I gave):

(from here: http://www.emanator.demon.co.uk/bigclive/fibre.htm) but its possible some of the components can be eliminated[/quote]

 

[baldelectrician]

buy a switch with a neon in it, strip out and you have it all ready made.

Make life easier

 

[Spark123]

Cool website adam, I would treat this experiment with a bit cautiously at first looking at the other things on there, http://www.emanator.demon.co.uk/bigclive/makendo.htm

USB turd

 

[Adam_151]

Lol, some of the things on there were of questionable safety, but I can't see anything wrong with this supply circuit (other than the fact that its not electrically separateated from the supply)

from: http://www.emanator.demon.co.uk/bigclive/halogen.htm :-

Being an electrician to trade, I've got absolutely no sense of electrical safety at all and decided to make a bare chandelier that operates at 240V

 

[Spark123]

Think I might try exploding smarties, now where did I put that gunpowder