Doubt it, I have not had one of those 1N914 diodes fail in nearly 17 years on metering led potential circuits.

The resistors take care of the voltage drop.

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Electricity, Electric clocks, Meters and Trains are great.

 

fever

Basically put 2 strings of 10 LED's in anti parrallel. for a 20 LED lamp.

For white LED's that is about 30 Volts drop, You need to get rid of ( 220-30 ) = 190 Volts in the series resistors. Run these at 5.75 mA than a 33 k ohm resistor would suffice. From U=I*R 190 / 33000 = 5.75 mA.
Power rating P=I²R then 0.00575² * 33000 = 1.1 Watts dissipated in the series R's.

I would go for 2 * 15 or 18 k. ohm 1 or 2 Watt series resistors to spread the heat a little.

For your 5 Led lamp I would put 2 Led's in forward mode and 3 Leds in reverse. Then use a 39 k ohm series resistor. or make it up from 2 * 22 k Ohms.

It is good practise to check the actual LED current in your circuit with your multi meter.

I find that most high efficiency LED's give excellent brightness at 5 to 8 mA's.
and i only have used 3000 to 5000 MCAD Led's.

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More to the point, the LED's mean there's only a small voltage across the diodes - the resistors simply limit the current.

No problem using those diodes!.

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A blocking diode is put in series to block off the voltage. This need to be rated higher than the applied voltage.

A by-passing diode, which is connected in anti-parallel with the LED, would reduce the reversed voltage across the LED because of its forward voltage drop of 0.6V.

I was referring to the first case.

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@RODALCO

i made a simple circuit diagram.pls have a look and let me know abt the mistakes.
http://img20.imageshack.us/img20/7014/wena9.jpg

and for application i will run this setup for 12 to 15 Hrs.so is it safe.

 

It won't work.

Attached Images

LED strings.PNG (91.7 KB, 27 views)

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Uncle $crooge

 

Thanks Audioguru for your quick reply to fevers question.

Correct! it won't work.

Just in words now.

[Phase] - [18 kOhm 1 Watt R] - [LED LED LED LED LED ....... LED biassed one way in parrallel with LED LED LED ....LED reversed way] - [18 kOhm 1 Watt] - [Neutral].

I haven't got a drawing programme so i will take a photo and add it later.

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thanks.even a rough paintbrush image is sufficient for me.i'll make good one with eagle.
(make a rough sketch for both 20,5 led application)

 

See if these GIF images come out.

Downloaded some drawing programme

Regards, Raymond

Attached Images

	5 Led lamp 1.GIF (16.9 KB, 28 views)
	20 Led lamp.GIF (20.3 KB, 22 views)

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There are more ways to get to Rome.

Electricity, Electric clocks, Meters and Trains are great.

 

thanks for the circuit diagram.
but the 4148 and 4007 diodes are missing.4007 is in series with the phase side resistor but what abt the 4148.how shld i connect it.

and is the resistor the only thing which decides the life of the whole circuit?
bcz till now i used ur circuit for only 1 LED(since 1year with continuous usage of at least 10Hrs)
20 LED circuit will draw pretty amount of current.so is this circuit suitable for 10-12Hrs operation?

 

They aren't needed because half the LEDs limit the reverse voltage for the other half of the LEDs in this AC circuit.

Calculate how low is the LED current. The peak current is only 7mA and 8mA. The average current is less than 3mA. LEDs are rated for continuous operation at 20mA and their max allowed continuous current is 30mA.

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Uncle $crooge

 

Hi Rodalco,

I would feel a lot more confortable if the leds were connected
antiparallel, it's the only way to be make sure that the reverse
voltage is evenly divided amongst all leds.
Or is it just me being paranoid ?

on1aag.

Attached Images

20 led circuit.GIF (4.9 KB, 24 views)

 

Thanks audioguru for your quick reply,

In between posts here on this forum we had a 10 MVA, 33 kV / 11 kV substation blow up in my area and lost power for 3 hours.
I was called out to do power restoration HV switching and fault assesment of the transformer. cause, overload and old cable

on1aag

You can do it the way you suggested as well, each pair of LED's in antiparrallel and make up a series string with 10 of those LED pairs.

It is interesting how a DC LED lamp topic turns out into an AC LED lamp topic. Still good to keep all bits together.

Regards, Ray

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Electricity, Electric clocks, Meters and Trains are great.

 

120 VAC to LEDs
Look up On Semiconductor NUD4011.
Figure 8 of the data sheet shows:
Full wave bridge
IC
Resistor ¼ watt
LEDs