how to operate an l.e.d.from 230 volts 5mA 50 cycles per second a.c. power source

Circuit in posted in 17 working several years for me, I didnt notice any changes on used LED, circuit is 24h on.

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As I said, I can swear. Unfortunately, reliable operation can't be concluded from the specification.

An approvals body, such as BSI, would want a circuit that can safely survive a single component failure in a mains-powered circuit (they call low voltage as under 42V). Appliances around you marked with approvals will be designed to like that. They would reject the 1-diode/1-resistor instantly, I'm afraid.

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Safety exactly in which regard? A "safety analysis" without an explicite safety objective is pointless as well. I can imagine a lot of cases where redundancy regarding either voltage or current limiting (or both of it) function is required, as well as any kind of reliable circuit function. Some applications will e.g. demand three diodes in parallel, using fail-safe mounting technology etc.

The low voltage diode point matters e.g. for the bridge rectifier, where a smaller (SOT-143) case can be used.

tpetar said:

Circuit in posted in 17 working several years for me, I didnt notice any changes on used LED, circuit is 24h on.

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I'm sure it does and that's good. But like I said above, you'd never get it approved and I think it's much more valuable on a forum to give an example and explanation of a circuit that will, that you can make hundreds of thousands of. That way we can show the reasoning and method behind designing for all requirements here: glowing, safety, approvable. Unfortunately we're getting stuck on 'glowing' as the only requirement.

I'm sure there's houses with an exposed live wire in a room that no-one's touched for 17 years and got a shock off of

I have sat and watched BSI come in for a morning to check out power supplies and ac motors in our new machines. They study the circuit then solder a short circuit across a single component or cut a leg, then switch it on to watch what it does. They keep doing this. If they're not happy, no approval and we couldn't sell the machine so no money. We had to meet UL, VDE, later for CE...it is a very real thing when designing for mains, I'm afraid.

What do you mean by "safety"? In the circuits that have been proposed, a component failure won't result in anything worse than the LED being damaged, or just not lighting. There is no risk to life or property.

The commonly used alternative is a single resistor in series with a neon lamp. I don't see how that is in any way "safer" but there is no problem with certification.

TonyM approval or certification is not goal for main question. We just go far from starting question :

Hello sir

I simply want to operate a single blue or green l.e.d. by means of 230v a.c. source without using any condenser so get me a simple circuit diagram without complications & easy to implant within a small pin plug.I made one with a single green l.e.d. in series with 100k resistor but the l.e.d. was damaged in two days so please help me
Thanks

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One more thought about the parallel diode circuit. The resistor is providing reliable current limiting. I don't see, why anyone would require a higher current or reverse voltage rating for diode D1 than for the LED D2 itself. Both numbers are higher by a factor of 10 or so for 1N4148.

From Starting Question, design points are:

led
no condenser
230 ac source

...and all that goes with running off 230V ac - electrical safety is inherent, I'm afraid

I've explained my approach several times in previous messages so I'll leave it there, all written already and this is only a discussion, on a forum.

But an led, 2-4 resistors and two diodes will make a circuit that meets the requirements for electrical safety. If our friend who asked has to do this in his job, or anyone else reading this, then the description I posted yay back will hopefully show what goes into such a design.

If anyone else is really determined to use 100V diodes in mains applications instead of cheap 400V ones, then it's a free world

Signing off this one...

If anyone else is really determined to use 100V diodes in mains applications instead of cheap 400V ones, then it's a free world.

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The consideration ignores the diode circuit function, which is not asking for the reverse voltage rating at all. Otherwise a LED, which is essentially a "5V diode" must not be used in "mains applications" at all.

The other relevant consideration is that 400V diodes are not available to the OP.

I'm sure he can get a few diodes like 1N4004-5-6-7

At last - thank you alexan_e

TonyM said:

At last - thank you alexan_e

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I thought you were "Signing off this one..."
I guess you can't resist...;-)

alexan_e said:

I'm sure he can get a few diodes like 1N4004-5-6-7

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Maybe, but he did say:

rajaram04 said:

...i didn't find any 400 v range IN4007 diode now what to do sir ?

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Hence the suggested circuits that don't require high voltage diodes.

Maybe we are over-complicating the issue, if he can't find diodes maybe a mains bulb indicator will be easier for him to find and use.

alexan_e said:

I thought you were "Signing off this one..."
I guess you can't resist...;-)

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Had to exit with a grateful nod to your constructive comment Best wishes, everyone...