LED Questions

[Lights4Tikes]

Simple question but very confused?

1/2 wave or full wave, what is the difference?

[HowardShank]

Check out this diagram. It explains the difference. The comopany that created the image used a fancy term "Richwave" that they've trademarked... it's the same thing as the boring term Full-Wave.

http://www.inirgee.com/images/RichWave%20LED%20Technical%2072.gif

[Max-Paul]

Not picking on you Howard, but that diagram really stunk. Although it does not really matter, but as I was going through Tech School, the humps or half waves were always drawn on the top side of the zero reference. But what was really bad about that diagram is that we are talking about the rectification of an A.C. signal to a raw D.C. current. Thus both half waves should have been on the same side of the zero reference line. And maybe my eyes are going bad real fast, but I could hardly make out the text. I can only presume that on the second box, the half wave part of the diagram that the word "off" was above the reference line and "on" was below the reference line. Thus only half of the sine wave was "on". And the third box showing what was suppose to be the full wave (rectified sine). That for each half of the signal that it was "on". Thus we have full wave, meaning that there is no lose of any of the wave like in the second box were half of the wave there is no current flow.

So, to answer the OP's question. And I personally have not been exposed to enough LED light strings to make a call, but only repeating what I have read in the forums. It is somes opinion that Full wave LEDs are brighter due to it always receiving current, unlike the half wave LEDs only receiving current for half of the wave. Some have also made the comment that they can detect a flickering of the half wave LEDs, where there is no detectable flickering of the full wave LEDs.

Thats all that I know on this subject.

Max

[Dale J]

Max, i agree nice explanation, i think the blinking of the led's is the main difference. i always hated the movies theaters that have the half wave led's along the stairs they really blink.

[Dennis Cherry]

Been using LED's since being introduced many years ago.

Our term for Half Wave and Full Wave is using it on a AC line. Also LED's run well on Filtered DC, but not for our use in animation. Even on the DC boards the voltage is a variable Pulse Width.

What I see on that web site is not new to LED strings. I see them confusing the issue showing the input current used on a Full wave string. Even if the string of lights has two independent strings of lights ie. 50 Led string will have 2 twenty five LED light string. There are exceptions, some colors like RED, Orange, Yellow may only have one continuous string of lights.

As for the flicker on LED's both Full and Half wave LED's do flicker. Try it yourself.

Take a Half wave string, plug it in and them take about a 3-4 foot length of the string between your hands then move it like a jump rope. What you will see is dashes of Light. Now take a string of Full wave LED's and do the same thing. Again you will see dashes of light but twice as many. Half wave LED's turn on and of 60 times a second, Full wave turn on and off 120 times a second. The normal human eye has a hard time seeing any flicker above 10 times a second. That is if you are just looking at the LED's. Move your head side to side and you might start seeing the flicker, just like the test above. Some people can see flicker higher than others.

If the LED's are operating on filtered DC, you will see a continuous line of light.

I explain it this way because most Full Wave LED strings may have modules in line with the light strings. There can be 1, 2, or 3 modules on the string. Some full wave strings are now coming without the modules, they are putting the steering diodes in the plug and receptacle housings.

Also some modules on the LED strings may not make the LED's full wave, cheaper strings will have one or two modules but what is inside the module is not steering diodes, but just a current limiting resistor. The test above will help you determine is this is the case.

It sounds confusing, and you are correct. LED Christmas lights are a fairly new product and still the manufacturers and designers have a learning curve. We have experienced good and bad designs the past couple of years. What is being made now is far better than say 3-4 years ago. Everyone is learning as technology changes.

There is more but that's enough for this post

[HowardShank]

I'm sorry the image sucks. It's just one that I found on the Internet.

Regardless of the technical validity of it, it expresses the idea of what happens for half and full wave LED's. Full wave are on nearly 100% of the time and half-wave led's are on only half of the time.

[Steven]

Dennis Cherry wrote:

The normal human eye has a hard time seeing any flicker above 10 times a second. That is if you are just looking at the LED's. Move your head side to side and you might start seeing the flicker, just like the test above. Some people can see flicker higher than others.

The human eye, like the eye of many animals, has evolved to see detail at the focus point (straight ahead), and to be very good at detecting motion at the periphery. This lets us detect a potential threat (such as a predator in prehistoric times or an automobile in modern times) before we're looking directly at it. In the peripheral vision, where there is no detail, motion is detected as rapid variation in the intensity of light. The center of vision can't detect this rapid variation as much.

We tend to look straight at something to learn more about it, but when we're trying to learn how much it flickers, it is better to look to the side. Wikipedia says flicker can be sensed in peripheral vision at higher frequencies than in foveal vision. A half-wave LED flickers at 60 Hz, which is higher than the flicker fusion threshold for central vision, but not in some people's peripheral vision. It depends on several factors.

[Ponddude]

Steven wrote:

Dennis Cherry wrote:

The normal human eye has a hard time seeing any flicker above 10 times a second. That is if you are just looking at the LED's. Move your head side to side and you might start seeing the flicker, just like the test above. Some people can see flicker higher than others.

The human eye, like the eye of many animals, has evolved to see detail at the focus point (straight ahead), and to be very good at detecting motion at the periphery.  This lets us detect a potential threat (such as a predator in prehistoric times or an automobile in modern times) before we're looking directly at it.  In the peripheral vision, where there is no detail, motion is detected as rapid variation in the intensity of light.  The center of vision can't detect this rapid variation as much.

We tend to look straight at something to learn more about it, but when we're trying to learn how much it flickers, it is better to look to the side.  Wikipedia says flicker can be sensed in peripheral vision at higher frequencies than in foveal vision.  A half-wave LED flickers at 60 Hz, which is higher than the flicker fusion threshold for central vision, but not in some people's peripheral vision.  It depends on several factors.

Are you an eye doctor?LOL

[lightzilla]

I cannot give you a better answer than what was already said, but not all full wave or half wave light strings are the same.

I have a number of LEDs from Walmart here in Canada that are 1/2 wave but look great and the flicker does not seem to be all that bad plus after 4 years none have burnt out as of yet.

I bought some 1/2 wave from Home Depot here in Canada and they stink big time, they flicker, and they burn out, plus they are a bit duller as well.

I bought some 1/2 wave from Canada's Rona store and they too are fairly decent and have some plastic coating that covers the socket area for added water proof protection.

I also picked up some LEDs from a store here called Real Canadian superstore in January 2008 for the tree in the house for $0.75 a box of 70 count 1/2 wave and when December came buy I put something like6 boxes of these on the tree and they were actually bright for 1/2 wave and I was impressed.......so I bought about 40 boxes of those LEDs in January (but outdoor LEDs) at $5.00 per box of 70 count.......blue, 1/2 price.....could not wait as they were beginning to go fast.

Now I bought a brand called Forever Bright (Full Wave) and they are very bright but they do burn out, even though there is very little flicker. Good to use on mini trees with 420 LEDs on it of 1 colour.

You do not get to see those few burnt out LEDs.

Now Costco Canada sold LEDs, in Red, blue, multi, and pure white last fall with prices between $7.99 for red to $10.00 for pure white in early October......so I thought, heck for Canada that is not a bad price for 1/2 wave 70 count strings......so I bought 16 boxes of Red, 16 boxes of Blue, and 16 boxes of pure white....for my mini mega tree.

Now all the boxes were sealed in plastic and the store was getting busier by the minute so I did not check them out until I got home, and when I opened 1 box of each colour I noticed 3 rectifiers on each string and was very happy, and when I plugged them in I was very happy at such a brilliant, radiant, glow of each string.

They were all full wave C6 light strings....with a top price of $10.00 per box for white , blue, multi coloured and $7.00 for the reds. There LED net lights were $9.00 per box for a 100 count net.

Anyhow I was so impressed that I bought in total 90 boxes of LEDs lights from them.
Just to let you know I had no issue with their lights even though some were buried in 12 inches of snow for a few day, and very, very cold temps of -35F weather for all of December last year...even colder on about 6 days in that month. None burnt out.

I hope and pray they sell the same brand again this year. I have enough money saved up for another 90 boxes....but all I need is 83 boxes to hit 24,000 lights (doubled my light count from last year).....but 21,000 is what I really need.

[Max-Paul]

Dennis,

Is this "Steering Diode" a new name for diodes that rectify A.C. into D.C. either half wave or full wave? When I went through technical school about 33 yrs ago, we called them Rectifiers, or diodes.

While writing this reply, I did a quick google and found this

http://www.protekdevices.com/applicationNotes00.htm

Scroll down to note #3. Is this what you are talking about?

I like to try to keep up with all of the new technical terms and this one has got me baffled.

Thanks
Max

[Dennis Cherry]

Max-Paul wrote:

Dennis,

Is this "Steering Diode" a new name for diodes that rectify A.C. into D.C. either half wave or full wave? When I went through technical school about 33 yrs ago, we called them Rectifiers, or diodes.

While writing this reply, I did a quick google and found this

http://www.protekdevices.com/applicationNotes00.htm

Scroll down to note #3. Is this what you are talking about?

I like to try to keep up with all of the new technical terms and this one has got me baffled.

Thanks
Max

I was trying to use a term that would explain how the negative swing of the AC sine wave was converted to the positive side. Maybe not the best use of the word "steering" in electronic terms.

Thought "steering" would be understandable.

HWR Led's actually do not need any diodes added to the string, LED's are diodes and work like diodes in only conducting in one direction. Going Full Wave you will need 4 diodes to make a bridge rectifier circuit. This can be done having 2 diodes (1/2 the bridge diode circuit) in the first part of the string and the other 2 diodes in the last part of the string.

You can also just use a small 1-1.5 amp bridge rectifier in the first part of the string. If your LED light string has two strings of LED's then the single bridge rectifier will not work unless you reverse the wiring on the second string. This is dangerous unless you know how to properly re-wire and protect the connections against shock hazard.

[toddmoon]

While shopping online for LED light special I ran across a site that claims that using fades on LED's will cut there life in half because they are designed for on and off not for fading.

Does anyone have any experience with this. I like the effects of the LED's and the traditional lights have there place as well. I have been trying to replace my existing lights with LEDs as they burn out or break.

If fading shortens the life of the LEDs I may need to rethink my use of LEDs.

[Dennis Cherry]

toddmoon wrote:

While shopping online for LED light special I ran across a site that claims that using fades on LED's will cut there life in half because they are designed for on and off not for fading.

Does anyone have any experience with this. I like the effects of the LED's and the traditional lights have there place as well. I have been trying to replace my existing lights with LEDs as they burn out or break.

If fading shortens the life of the LEDs I may need to rethink my use of LEDs.

Initially LED's where made as indicator lights on electronic equipment operating on filtered DC voltage, then the designers of circuits started using pulsed DC on the LED's to reduce the average power of the equipment and make the LED's do other functions beside just on and off.

LED's do fade but not exactly like a incandescent lamp. If fading was a problem we would not be using them in our displays. Some brands of LED strings may not be using good quality LED's or design practices as per previous post have indicated. but if you buy from known good suppliers your should not have issues with LED's going bad.

[Max-Paul]

I agree that fading and just turning LEDs on and off will make them fail sooner. Just like a regular filiment light bulb will fail sooner. Even though LEDs do not draw nearly as much wattage as a filiment lamp does. It still causes some local heating up of the componets of the LED. Heat causes things to expand and the removel of heat causes things to contract. Eventually the die will seperate from the lead or the little lead contacting the die will break off. But due to much lower wattage, the thermo expantion and contraction will be less. And the life of the LED will still in most cases be much longer than a filiment bulb. Plus every year you put up LEDs the color will not change or so little you wont notice. Say that is so of your filiment bulbs? Also the chances of an LED string going bad versus a filiment string going black because a bulb burnt out (ya actually I think it takes 2 or more).

It might take me longer to build up my display, but I am going 100% LED. Also, I dont have to have a nuke power plant in my back yard to power up my display. More cash in my wallet and not in the utilities.

[Steven]

Do you ever wonder what's inside those "bumps" on LED strings? One wasn't working, so I took it apart. The colors don't show up well in the picture, but that's a 620Ω, 1W resistor. There appears to be another at the other end of this series-parallel group in series.


Attached files

[Max-Paul]

Hi Steven,

Just got some of my LEDs from Travis. And that is the same construction as mine. And yes, I was wondering if that was just a splice point or what. I dont have a desire to destroy a string to find out just how the string is wired so I have no idea. Are both wires from the LEDs on one side of resistor? So, this leaves me with the question, what is the large wire wart near the male plug? Is that just a choke, and these strings are not true FW?

Thanks for sharing the above info.

[Steven]

This is one of the strings from Travis. It happened to be the first out of the box, and it was defective. The last half of the string flickered weakly. I was worried, but the other 18 strings seem to be working. I needed a 50-bulb string anyway, so I just removed the defective half of the string and used the first half for my star.

The wire from the nearest LED is connected to one side of the resistor, and the other side is soldered to the other wire that passes entirely through the bump. It's actually one piece of wire with enough insulation removed so it can be soldered to the resistor.

The bump on the male end is a full wave bridge rectifier. I didn't destroy that part since it's still working, but I was able to deduce what it is by putting a voltmeter on the female end, which reads about 140 VDC when the string is plugged in. The other bumps seem to all be the same 620Ω resistor, deduced by the fact that each one reaches about the same temperature when plugged in.

The lights themselves are connected as 25 pairs in series. Each pair is connected in parallel. You can see this as each pair of LEDs has two wires connecting the pair. This configuration is patented. It allows one light to fail open while keeping the other lights lit by having twice the current flow through the working LED in the pair.

[Max-Paul]

Thanks Steven,

I was wondering how they were going to get 120VAC out at the female socket. It just was not adding up. And I just had not taken the time to put my DVM at the socket. Well that tells me that I do not want to plug in anything that is rated for 120VAC at the end of the string. And thanks for analyzing the circuit path through the string.

[Steven]

Max-Paul wrote:

Well that tells me that I do not want to plug in anything that is rated for 120VAC at the end of the string.

If you plug a half-wave LED string into that socket, it will be brighter and become a full-wave string. I did that last year with no problems.

[Max-Paul]

Ok, got me Steven, I was thinking along the lines of say something motorized like say a deer with the motor that makes the head/neck move.