Current limiting resistors limit current draw, not voltage. You will need the resistors.
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Current limiting resistors limit current draw, not voltage. You will need the resistors.
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The datasheet can be found here. They use 50mA so the whole string should only use 50mA.
I keep hearing all the time that things only take as much current as they need. So a 50mA string of LEDs will be fine on a 13A mains circuit. I read that they will only take too much current if i put too many volts into them.
The power in our house can be a bit strange. We are supposed to be getting only 230V but ive never seen it drop below 240 and quite often its as high as 250. Dips wont be a problem and spikes should be fine as i could put over 300V into the string and still be within the max voltage
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Don't do it.
As an experiment, put a string of LED's across your Car Battery without any form of Current Limiting - that's a reasonably constant voltage - then go rev your car engine up...
> Could i use 4 diodes to make a rectifier?
Yes
> The diodes are only meant for about 50V 1A.
Well that's kinda stupid to use them on 240v then!
> I found one thats 470N 250V. Would 470N be enough?
Depends on how much current you're pulling... but the 250v bit is totally inadequate, because by the time you full-wave rectify mains you'll have close to 340vDC.
Back to my first line... DON'T DO IT. You are running the risk of harming yourself, your property and putting at serious risk those around you.
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I double the Melanies post.
But if you insist on doing it, PLEASE promiss to have a camera on and with direct link to internet, so we can all see what happens the moment you turn the power ON!
Direct link is needed as you may not be able to send the video file later!
Anyway, some notes on he LED.
1. 50mA is the Absolute Maximum. So according o D.S., 30mA is the working conditions.
2. Each LED is different so a range of 3-4 volts is logiacal. BUT, if you have a source of 10 volts, then you calculate the 3.5 Volts/.03A to find the resistor that each led should have in order to balance its current.
3. A slight increase in Voltage will dramatically increase the current through LED as its characteristics are not Linear. It is NOT a resistor! It is a diode.
Now if you still want to do it, I would suggest:
WARNING All voltages are lethal!
1. Have a 4x1N4004 or 4007 diodes as a rectifier, or even better a bridge rectifier (4 pins) for 500Volts/2-5Amps.
2. On the AC line, fuse and a small resistor for the in-rush currents, say 2-5 ohms.
3. After rectification a capacitor of 220uF/500 Volts.
4. Calculate maximum voltage as 250 Vac x 1,41=353 Volts DC on te capacitor.
5. Calculate the total drop of LEDs say 332.5 Volts. Calculate the number of LEDs 332.5/3,5= 95 LEDs.
6. Calculate the resistor to be in series as (353 - 332.5)/.03 = 680 Ohms
7. Calculate the power of the resistor .03 x .03 x 680= 620mW. I would go x4 to set it at 2,5Watts
OK. We finished.
Hope you wear safety glasses and gloves because:
1. LEDS may explode if they get high voltage by accident
2 Every where on the circuit are very lethal voltages!
If you still want to do it, don't forget the Video Camera!
Ioannis
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Thanks for the info. I know the diodes are rated at 50V but my thinking was that the LEDs are rated at 3V and the diodes would be in series with them. Thats why i asked this seemingly silly question. I will make sure to use diodes suitable for mains.
It seems i give the impression that im willing to plug things into the mains without caring if it will explode or not. I do actually think about these things. I usually check here even if i know what im doing but i have a few doubts. I wont be plugging these LEDs right into the mains. I will start with lower voltages and step it up gradually. I wont be touching random parts of this circuit while its turned on. I have been working with mains voltages for many years and i know how painfull it can be. I will be as careful as i always am when dealing with high voltage
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Multiply this by 95 LED's and a lot more vicious...
OK... let's be helpful... look at this and follow instructions...
I absolutely trust this guy... here's a great tip from him on how to make your workplace smell nice...
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Don't forget that with all these LEDs in series that if one blows or goes high impedance (and they do change with time and temperature) they will all go off. Just like christmas tree lights.
Put say 10 of them in series and use a boost driver like the Sipex SP6691 or similar with current regulation.
8 banks of 10 will work much better than 1 bank of 80.
Your'e gonna have to be more careful than that!Originally Posted by The Master
Rectified mains is not forgiving at all. -Ask any qualified TV engineer.
Mains thats passed through a bridge rectifier will cause the resultant -v output to be at a half mains potential, and not ground as you would expect / hope.
Good luck.
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We are just concerned about your safety..
I will now sound like the old gezzer I am and say that I have been "playing" with high voltage/amps for I will bet more years than you have been alive.
I see NO reason to risk your health and safety doing something like this. I would not try it. To many things that can and probably will go wrong. Yes it can be done, but why? Just to say you did it?
Do like timmers suggested and run multiple strings from a lower voltage.
Dave
Always wear safety glasses while programming.
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Thanks for the links. I just need 4KV now... :P
I am considering running multiple smaller strings already but using 1 long string seems to be more efficient.
Im planning a few projects that will involve having hundreds of LEDs lighting up together. These LEDs use 50mA which adds up to quite a lot and i would probably need multiple transformers to run them all. Running them from the mains would mean theres no need for any transformers so it would be a lot cheaper
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