Putting safety issues aside for a minute, those LEDs are going to flicker like crazy @ 50/69 Hz.

No, they aren't.

Also, putting 100 LEDs in series is just nuts!

Not really. I replaced the fluorescent tubes in a basement light fixture with lotsa white LEDs in series just for fun. And commercial LED replacement tube lights are long series strings, granted with an actual power supply driving them.

 

Yes I did here and here.

If you read the two posts you linked, you will see they say that you are making the same mistake the TS did. They are correcting the TS for talking about a Whetstone bridge when he means diode bridge.

ak

 

All the one I see are 9VDC or 12VDC. How would they chase and do all sorts of patterns if what you say is true?

The animated ones tend to run off a 12V DC power supply, the simple ones (either all illuminated or a switch between "open" and "closed") are often straight off the mains.

 

You'll be far from the 240VDC he is expecting.

Who is "he"?
I think your attempted play-by-play commentary and really bad, I'll-informed "fact checking" is confusing the thread. Take a course on electronics and a class on forum etiquette (or general social skills). You must be a real charmer at a dinner party.

 

A small capacitor will solve that.

With a significant increase in harmonic content.

ak

 

That's not a problem since no authorities will get this approved anyways.

Why not? I have. LED's running directly off the mains are very common in night lights, room air fresheners, EXIT and other static signage, and some MIL-STD-704 system monitoring. Making such a device safe is neither difficult nor expensive. Certs can be expensive, but that's just a cost of doing business that also is required for low voltage systems.

ak

 

Didn't you read the thread before commenting?!? PLEASE read post #15 the TS informs us 240VAC once thru the rectifier will give him 240VDC. He follows by " What could go wrong ".

So you're saying your comment was about the wrong person? You keep replying to a person and pretend to address another person's comment. Please let me know which person you were talking about in your response to my older post.

 

That's not a problem since no authorities will get this approved anyways.

That's the dumbest comment I've ever heard - there are literally thousands of devices built around mains powered electronics, LEDs, and other BS. Are you trying to boost your post count or do you just enjoy seeing people react to your posts full of baseless claims of... everything?

 

The last time the TS was here was on post #26.
43 post later members are bickering among themselves as to who is right or wrong which is not constructive or helpful to the TS.

So knock it off fellas!

 

Never saw one straight off the mains in real life unless it was neon, must be regional. Most LED use 12VDC some 9VDC battery, none home made.

They are probably older ones. Once we got on to the flashing chasing ones, which needed a low voltage supply for the electronics, then manufacturers used the same supply for all of them; and realised that that had to be nowhere near as careful with the insulation!

 

http://imgur.com/a/11qHTO7

You probably can't see it from where you are, but your guide is leading you to danger and you're following in the footsteps of idiots. I have no doubt that's exactly how your your guide as well as some random people on the internet make LED signs, and I have no doubt that they work. But that is the electrical equivalent of strapping a propane tank to your bumper to power your car. And then selling the car to a family with 5 kids and two parents who don't know any better than to drive around with a gas bomb right in the place where it's most likely to get crushed and kill all of them. I'm sure you don't want to be responsible for the burning down of any of your clients homes and/or businesses, so please abandon this idea as literally every person on this is recommending or would recommend, and use a proper LED power supply.

So again, how many LEDs, what kind?

http://imgur.com/a/11qHTO7

 

They'll flicker at 100Hz, not 50Hz; which is a lot less noticeable. Plenty of those LEDs signs you see that say "open" or "closed" or "cold beer" (though we don't like cold beer over here) are all in series off straight off the mains. They are in a plastic box, behind an arcylic panel, so are perfectly safe.
True, if one LED fails, they all go off, but it's possible to find the faulty one quite quickly with a "binary search" technique; but LEDs don't tend to fail within the guarantee period of the sign.

this is exactly what I intend to do. but instead of acrylic, it's plywood, all wooden, with a plastic casing

 

Several things. Among other things, the output of your bridge rectifier will be 340 Volts peak. For another, the difference between the forward voltage drop (Vf) of a red LED compared to a white LED is only ***100%***.

But your biggest problem is that you are equating a flashlight with a Las Vegas light show. The hundreds of LEDs in the video you posted are *individually addressable*. They are *not* 100 LEDs in s single series circuit with one current limiting resistor. You are correct that that can work - if all you want is one big light. But the video shows hundreds of LEDs, each with its own individual driver and current limiting circuit, being turned on and off under computer control. All sign boards are variations of the same theme.

In your circuit with 100 LEDs in series with one bridge and one resistor, how would you turn on only the even numbered ones? Or only every 10th one? 105 LEDs is enough for three 5x7 dot character blocks. With only one string through everything, how would you get that string to display "abc"?

ak

this is it, wiresin the backside continue the series for 100 bulbs

 

hi dev,
For reference only.
E

 

btw I'm using 5mm LEDs

 

hi dev,
Note the range of 'light output' mcd for the various LED's of the same colour.
Choose the types that give a brighter light output per buck,, the display characters will look more evenly lit..
E
5mm's LED

 

The light output in lumens would be more useful than the brightness in candela, because the table doesn't specify the viewing angle. Not much use having a sign that is ten times brighter, but only visible over a 10° angle in front of it; unless, of course, it's at the side of the road facing oncoming traffic.
Bear in mind that the optical parameters (lumens, candela , lux) are based on the human eye response, so long and short wavelength colours will always appear less "efficient".
Also I wouldn't classify 402nm as "UV" as the visible spectrum is usually defined as starting at 400nm. UV, being invisible, is zero when measured in candela.

 

this is it, wiresin the backside continue the series for 100 bulbs

Up until now, I thought you were building a programmable sign. If the text is fixed, then you can indeed have many LEDs in series with a single current limiting resistor. You are correct that the vast majority of people will not notice the flicker. And as above, a small filter capacitor will reduce it to almost nothing.

Not to be picky, but the first apostrophe, before the N, is incorrect. It should be curved the same direction as the one after the N. Before-and-after quotation marks curve differently; apostrophes do not.

ak

 

A fellow grammar- and punctuation-pedant!

 

Up until now, I thought you were building a programmable sign. If the text is fixed, then you can indeed have many LEDs in series with a single current limiting resistor. You are correct that the vast majority of people will not notice the flicker. And as above, a small filter capacitor will reduce it to almost nothing.

Not to be picky, but the first apostrophe, before the N, is incorrect. It should be curved the same direction as the one after the N. Before-and-after quotation marks curve differently; apostrophes do not.

ak

And a "T" shouldn't look like little umbrellas - unless the client said they should. Maybe the single quote marks are also client-specified.