Any advantage to use DC to power LED strings?

[tbone321]

First off the AC frequency is 60 hz, in half wave strings the LED's are turning OFF and ON 60 times a second not 30. In Full wave they are turning OFF and ON at 120 times per second. Think about it?

For dimming differences Yes there is a slight difference, that's why I mentioned you test you LED strings using a Console hardware program to get a feel for your lights, even put a couple of strings on mini's or C7's to compare the dimming.

Mu display in 2010 I had a sequence that accidentally had a 1% value on all strings instead of 0% OFF. what surprised me was the nice soft glow the LED gave to the house. Could not see any flicker at 1% on either Full or Half Wave LED's. People like the effect it gave the song.

Now not all LED's light strings will turn on at 1% it has to do with many factors which would take to long to explain and understand, but the BLUE LED's along with the RED did barely come on, but Green and White did not. So with the accident of the 1% value my display had a background glow of BLUE and was dominant over the RED. I have a video of it but my camera is not really the best for showing how it really looked.

One other thing the controller design has a lot to do with how the LED's work. The Lynx by far has a better design for LED's than the LOR or Renard designs IMHO.  The Lynx V5 already has the needed snubbers included to prevent the inductive load of the LED strings form letting the misfire of the traics from happening during fades or anytime.

The best advice is test, test, test so you know how your display will operate before the season starts.

We can go around and around with this but it is really pointless to do so.  What I was trying to say with the 30Hz thing was that a 1/2 wave set blinks at half the speed of a full wave set or like a full wave set operating at 30Hz.  You made it sound like 60Hz is 60Hz and there is no difference between the half and full wave sets with dimming and that simply is not true.  Yes, they are doing the same thing but and oddities between the LED and Icans in dimming is going to be amplified by the halfwave set.  I am aware of how LED's work and I know that different colors have different turn on voltages and even the same color from different manufacturers can have slightly different turn on voltages and will not all turn on at 1% but that is not the issue.  The issue is that the dimming issues with LED's running on AC are amplified to some degree with half wave sets and the slower blink rate does effect some people.  If this were not true, why would full wave sets ever be created?  What would be the point spending more money adding unneeded parts to the strings and icreasing the number of points of failure for no benefit?  Many people in here have claimed that their half wave sets don't dim well and that was my point. 

[Dennis Cherry]

First off the AC frequency is 60 hz, in half wave strings the LED's are turning OFF and ON 60 times a second not 30. In Full wave they are turning OFF and ON at 120 times per second. Think about it?

For dimming differences Yes there is a slight difference, that's why I mentioned you test you LED strings using a Console hardware program to get a feel for your lights, even put a couple of strings on mini's or C7's to compare the dimming.

Mu display in 2010 I had a sequence that accidentally had a 1% value on all strings instead of 0% OFF. what surprised me was the nice soft glow the LED gave to the house. Could not see any flicker at 1% on either Full or Half Wave LED's. People like the effect it gave the song.

Now not all LED's light strings will turn on at 1% it has to do with many factors which would take to long to explain and understand, but the BLUE LED's along with the RED did barely come on, but Green and White did not. So with the accident of the 1% value my display had a background glow of BLUE and was dominant over the RED. I have a video of it but my camera is not really the best for showing how it really looked.

One other thing the controller design has a lot to do with how the LED's work. The Lynx by far has a better design for LED's than the LOR or Renard designs IMHO.  The Lynx V5 already has the needed snubbers included to prevent the inductive load of the LED strings form letting the misfire of the traics from happening during fades or anytime.

The best advice is test, test, test so you know how your display will operate before the season starts.

We can go around and around with this but it is really pointless to do so.  What I was trying to say with the 30Hz thing was that a 1/2 wave set blinks at half the speed of a full wave set or like a full wave set operating at 30Hz.  You made it sound like 60Hz is 60Hz and there is no difference between the half and full wave sets with dimming and that simply is not true.  Yes, they are doing the same thing but and oddities between the LED and Icans in dimming is going to be amplified by the halfwave set.  I am aware of how LED's work and I know that different colors have different turn on voltages and even the same color from different manufacturers can have slightly different turn on voltages and will not all turn on at 1% but that is not the issue.  The issue is that the dimming issues with LED's running on AC are amplified to some degree with half wave sets and the slower blink rate does effect some people.  If this were not true, why would full wave sets ever be created?  What would be the point spending more money adding unneeded parts to the strings and icreasing the number of points of failure for no benefit?  Many people in here have claimed that their half wave sets don't dim well and that was my point.

DELETED my response.

This will be my last post on this thread.

[sirloinofbeef001]

 

[Rogelio]

I do appreciate everyone's responses.   This will be my first build.  As with most everything I guess it really comes down to personal preference.
Thanks again.
Roy

[Zeph]

personally, when i look at half wave lights, they appear dimmer, and hurt my eyes if i look at them for more than a second.

I used an LED rope light under the kitchen cabinets, to light the counter.  It turned out to be half wave, and the light was definitely a little bit irritating to the eye, as they eye roams around.  Spouse was appreciative of the intent, but would only use them temporarily if something in a dark corner was needed.

I'm not going to splice in extra diodes in the rope light, so I inserted a full wave bridge between the AC power and the rope light - instant full wave.  Noticeably brighter (in a useful way), and much less flickery.  Spouse happy to use them. 

(I actually made the bridge rectifier as a box which inserts inline, so I can insert and remove it - and I've used it to test other LED lights; has a DPDT switch to reverse the polarity).

HOWEVER - in the process of testing and comparing I learned that the flickery irritation diminished with distance.  From the far end of the dining room (say, almost 30'), it wasn't much of any issue.  From immedidately in front of the counter (reflected light from 3' away), it was an issue.  Most outdoor Christmas light displays are seen from afar, so I wouldn't think there would be much problem in that case.  And the doubling of brightness from full wave would be less important, too, I would think (there is an optimal level of counter lighting, but our eyes have no standard for how bright christmas lights should be).

[rm357]

Most people either don't see or don't notice the flicker. Some of us are quite sensitive to it and find it horribly annoying - to the point that I cannot look at it long. Most half wave strings are pretty obvious to me unless they have included a decent size capacitor in the circuit to stretch the on cycle.

When we dim 60 Hz AC, you are actually dimming at 120 Hz - the triac is triggered on both the positive and negative going parts of the waveform and turns off at the zero crossing.

At 120 Hz, that puts the theoretical minimum dimming interval at 8.33ms with a resolution of 8.33 ms. 20ms updates will jitter between ~16.7ms and ~25ms - assuming the firmware can keep up with the updates...

BTW the wireless DMX module only updates at 50ms. If you are sending updates faster than that, some are being lost...

RM

[rm357]

Cool idea on the inline plug. Unless the LED plug is polarized, you could just reverse the plug rather than include a relay.
RM

[pk]

For my 2010 show I purchased some strings of 200 Multi-colored LED's from Sam's Club.  The string of 200 is made up of 4 individual strings of 33 and 2 strings of 34.  However, they are wired such that strings 1,3,and 5 are on during the positive 1/2 cycle and strings 2, 4, and 6 are on during the negative 1/2 cycle.

Last month I converted one of the strings to full wave to see what difference it would make.  I added a full wave bridge rectifier, and do to the way the string was wired, I had to reverse the connections to each section.  I got the string of 200 converted and did some testing.

My empirical observation was the full wave string was brighter.  This makes sense since each LED is ON during both half-cycles. 

When a LED of the 1/2 wave string is moved rapidly, I observed a period of time when the LED was on and a period of time when it was off, a - - - type of look.  I observed the same on the full wave string but the OFF time was reduced,  It appeared as a ---- .  The off portion of the full wave string is due to the fact that there is a minimum voltage required to turn the string of 33 LED's on. The rectified AC voltage does drop below this value thus the off time for the LEDs.

I connected both strings to the same channel of an express to see how they dimmed.  In my opinion, the full wave string dimmed better but keep in mind it is also brighter.  DLA member mms was present when the testing was done and perhaps me would like to add his 2 cents worth.

I also connected the full wave string to a 120 VDC supply that I have.  When the LEDs were moved rapidly, the LEDs were on continuously - no off time period was observed.  This makes sense since the voltage is constant and never drops below the minimum value needed to turn the string on. 

[mms]

For my 2010 show I purchased some strings of 200 Multi-colored LED's from Sam's Club.  The string of 200 is made up of 4 individual strings of 33 and 2 strings of 34.  However, they are wired such that strings 1,3,and 5 are on during the positive 1/2 cycle and strings 2, 4, and 6 are on during the negative 1/2 cycle.

Last month I converted one of the strings to full wave to see what difference it would make.  I added a full wave bridge rectifier, and do to the way the string was wired, I had to reverse the connections to each section.  I got the string of 200 converted and did some testing.

My empirical observation was the full wave string was brighter.  This makes sense since each LED is ON during both half-cycles. 

When a LED of the 1/2 wave string is moved rapidly, I observed a period of time when the LED was on and a period of time when it was off, a - - - type of look.  I observed the same on the full wave string but the OFF time was reduced,  It appeared as a ---- .  The off portion of the full wave string is due to the fact that there is a minimum voltage required to turn the string of 33 LED's on. The rectified AC voltage does drop below this value thus the off time for the LEDs.

I connected both strings to the same channel of an express to see how they dimmed.  In my opinion, the full wave string dimmed better but keep in mind it is also brighter.  DLA member mms was present when the testing was done and perhaps me would like to add his 2 cents worth.

I also connected the full wave string to a 120 VDC supply that I have.  When the LEDs were moved rapidly, the LEDs were on continuously - no off time period was observed.  This makes sense since the voltage is constant and never drops below the minimum value needed to turn the string on.

IMHO, the full wave LEDs were not only brighter but also seemed to have a greater range from off to full brightness.  Half wave LEDs "step" on.  For instance, on a variety of the curves in the Lynx config utility when you move the slider to "1" the LEDs are say 1/4 full brightness.  At 35 there's another step, etc.  The full wave LEDs were barely on at 1 and performed closer to how an incandescent string performs in a ramp up/fade down scenario.

I have some C7 LED strings that I bought a few years ago.  The "steps" are very noticeable.  So much so, that watching them in my show this year was a distraction to me.  I'm hoping we can convert these and post a video so that you can see for yourselves.