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Thread: Martha Stewart "Flicker Free" LED Strings

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    Havin fun ! kidcole's Avatar
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    Default Martha Stewart "Flicker Free" LED Strings

    For the past week or so I have been down a path with the Martha Stewart lights that "almost" turned into a bad thing. We have discussed these light strings a few times over the last year because they were the first commercial strings to finally advertise "flicker free." So as Paul Harvey used to say .. here's the "rest of the story."

    Home depot had a nice deal to trade in old light strings and get $4 off each set of Martha Stewart lights. So I bought 16 of the 50 bulb flicker free lights at $8 a string. I was planning to use them for my 12 channel Beth Star.

    I had hoped I would find a simply full wave rectifier inside one of the plugs. But when I pulled the strings out of the box, the wiring was very confusing. Each end of the strings had three wires coming out of the plug (and socket). This was not too surprising because obviously two of them were the passthru 120V AC lines. And they turned out to be that way. The Neutral was apparently a common return for the DC section.

    Then I noticed that every other bulb had an additional wire between them. Basically the string had three wires running all along .. but every other bulb had a 4th wire ! Al came by to help me with that one and with his help we quickly figured out the they wired every two bulbs in parallel so if one goes out the string stays lit. And that's how they describe the strings. But if you pull the second bulb also .. then the string goes out. This is a new twist on what the incandescent world call "Constant On" ..

    But now we still don't know where the rectifier is located. So I sacrificed one of my strings. << I had planned to cut 4 of the strings in half for segments of the Beth Star anyhow >>> This is where things got worrisome ! We pulled one end off and found a little circuit board. The board had only one diode, but it had two resistors and a dreaded Capacitor ! Holy crap .. certainly they could not be trying to use a smoothing cap to cut out the flicker? Some of the first companies to offer flicker free about 5 years ago did this and the caps blew up when you dimmed the bulbs .. OUCH ! Martha ! You're not taking us down this path again ?

    So we dug into the other end a peeled out another circuit board. But this one is laid out differently. There's a second diode, a couple more resistors, and holy shit another Capacitor. <Can I say holy shit here ?>

    At this point I now have my string totally dissected and it's starting to look like we can't dim these suckers with our LOR controllers. But there's a very nice set of technical specs and cautions on a sheet of paper in each set. And that included a phone number to the company that made these strings for Martha. By this time Al has us both convinced that we might be in trouble but he also left some room in the discussion for the possibility that someone came up with a better mousetrap. So I called them. The lady that answered was not an engineer but she was very nice and she wrote down that I wanted to run computer controlled DIMMing of the lights. About an hour ago she called me back and the design engineers said we should not have any trouble with dimming the Martha Stewart LED light strings. Whooooo Buddy .. we dodged that one !

    Although Al is not doing a show this year, he said if "Martha says those lights can be dimmed, then I would be very happy to draw out the circuits they are using, so we can analyze what they are doing." I am going to get the little circuit boards from Al and hopefully he'll find some time to post his findings here.

    Maybe they have found a better way to smooth the flicker and still be DIMMABLE. I would not say we are out of the woods yet. Because what happens if we dim them to 30% and leave them there for a few hours ? I know that the manufacturers don't like to just put in four diodes. And I am guessing that it's because they don't want to concentrate the current load at one point on the wire. Maybe this new <more elaborate> wiring accomplishes spreading the load and at the same time adds more time delay to the 30 cycle pulse ? It does not appear that they are using both sides of the wave. But we can discuss that once Al has drawn up the circuit boards for us.
    Thanks,

    Denny Cole
    https://www.facebook.com/groups/Cole...ristmasLights/

    Back to Work <unretired> so I went Static in 2017. Planning xLights when I retire <again>. Maybe 2019 ?

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    Space rented from Al SWood's Avatar
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    Default Re: Martha Stewart "Flicker Free" LED Strings

    Well I'll be S**t!! Lol. Hopefully that's a good sign because I bought 20 boxes of red and 20 boxes of green on that same deal. I mainly wanted to get rid of all my old incandescent strings. I don't know if you seen my post last week when I bought them, but I quoted you saying they were dimmable, that's why I jumped on them lol. I would be glad at the first of the year to run a string through some sequences for a few weeks if you think that might be necessary.

    Thanks for the info in these!

  3. #3
    This space for rent. Al in Raleigh's Avatar
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    Default Re: Martha Stewart "Flicker Free" LED Strings

    Without doing a circuit analysis and having empirical data, I would guess you could dim the strings if you reduced the amplitude using something like a variac. However, we don't using transformer amplitude reduction to dim them. Without examining the circuit, I would venture to say that PWM switching, triac switching in other words, doesn't like ripple filtration capacitors. PWM switching might work at certain "voltage levels" but by virtue of PWM switching into a non-inductive but capacitive circuit makes stuff go boom. The last part was for drama. I hope you were impressed.
    Al

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    Havin fun ! kidcole's Avatar
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    Default Re: Martha Stewart "Flicker Free" LED Strings

    I just plugged one in and started dimming it..
    .
    .
    .
    BOOM !!!
    .
    .
    .
    hahahahahaha !
    .
    Al, I'll bring the boards to you. Maybe they have created something new .. I hope ! We'll see who gets the right answer first. Either you (Al) by analysis, or us (those running the lights) by blowing one up ! I will not be bashful about returning them if I blow one up with dimming. But I have decided not to put them on my Beth Star, simply because it will be a lot of work to tear it back apart later ...
    Thanks,

    Denny Cole
    https://www.facebook.com/groups/Cole...ristmasLights/

    Back to Work <unretired> so I went Static in 2017. Planning xLights when I retire <again>. Maybe 2019 ?

    Falcon - 3 F16V3 & 1 PiCap, Sandevices - 2 E681 & 4 E6804, 288 Channels Lynx Express, 108 Channels DC DMX,
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    This space for rent. Al in Raleigh's Avatar
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    Default Re: Martha Stewart "Flicker Free" LED Strings

    Now that is drama. Nice job.

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    Registered User mschell's Avatar
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    Default Re: Martha Stewart "Flicker Free" LED Strings

    So are you saying they did dim OK, or did they actually blow up?

    I meant to try to get some of those strings with the trade-in, but other things got in the way...
    Mark

    New location - new display. Looking forward to 2015 season!

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    Space rented from Al SWood's Avatar
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    Default Re: Martha Stewart "Flicker Free" LED Strings

    Yeah, I wanna know too before i bring them in the house! LOL
    Shannon Wood
    XLights 4 User with 40,000 channels and 60,000 lights.
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    Default Re: Martha Stewart "Flicker Free" LED Strings

    If you don't know whether or not your strings are dimmable how long would a set typically last before you notice a problem?
    Shannon Wood
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    Havin fun ! kidcole's Avatar
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    Default Re: Martha Stewart "Flicker Free" LED Strings

    Ha ! I was kidding ... I have not tried yet. Looks like I need a test sequence to ramp them up and down.

    Al, any suggestions for what kind of patterns I might use to stress the crap out of them ?
    Thanks,

    Denny Cole
    https://www.facebook.com/groups/Cole...ristmasLights/

    Back to Work <unretired> so I went Static in 2017. Planning xLights when I retire <again>. Maybe 2019 ?

    Falcon - 3 F16V3 & 1 PiCap, Sandevices - 2 E681 & 4 E6804, 288 Channels Lynx Express, 108 Channels DC DMX,
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    This space for rent. Al in Raleigh's Avatar
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    Default Re: Martha Stewart "Flicker Free" LED Strings

    It may work okay if voltage is slow to transition such as a very slow fade. I wouldn't try it unless the string was outside laying on concrete so it wouldn't set something on fire. The capacitors (surprisingly I saw 2) are small enough that they shouldn't be a real boom. I would venture it would make a sppfffflllllttttt. Boom is melodramatic. Fire is a real possibility. It might even fry a triac channel since the di/dt is great enough to cause a momentary substantial inrush. I am speculating. I had a very brief look a the circuit board. It actually had 2 circuit boards, one on each end. Each contained a diode, resistor (or two), and a mylar cap. The resistors were 1/8 watt too to which I surmised to mean the power is being dropped in several areas to hinder an area of the string getting really hot and Bubba getting all bent out of shape because his Christmas LEDs got hot when Daddy's Christmas Lights never got hot and calling them "Chinese crap that Martha sells".

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    Space rented from Al SWood's Avatar
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    Default Re: Martha Stewart "Flicker Free" LED Strings

    Y'all got me scared now. I guess I'll sit out in a lawn chair until the shows over lol
    Shannon Wood
    XLights 4 User with 40,000 channels and 60,000 lights.
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    Senior Member mpurser's Avatar
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    Default Re: Martha Stewart "Flicker Free" LED Strings

    well glad i work at lowes no martha s. here

  13. #13
    This space for rent. Al in Raleigh's Avatar
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    Default Re: Martha Stewart "Flicker Free" LED Strings

    We looked at the circuit tonight. It has a ripple cap actually 2 ripple caps with 2 bleed resistors for the ripple caps. It is a very interesting circuit. I calculated a fairly short time constant for the ripple caps but how short. There are many variables namely the voltage of the LEDs etc that we don't have. All in all, it is my outhouse opinion that the ripple caps will not like fast transitions from a high voltage to a low voltage or in other words fading. It might do it just fine. Denny is going to run a couple tests. I told him to put the string on concrete for the test. If he blows up a controller I'll loan him a replacement until he can fix it.
    Al

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    Trying to behave here-NOT John's Avatar
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    Default Re: Martha Stewart "Flicker Free" LED Strings

    I would really like to know how well these will hold up on a "stress test" before failure.

    In 2008, this was real world. Strings would suddenly catch on fire.

    CDI switched mfg, and between the protype samples, and production run, some engineer changed the design without letting Paul know. Included a capacitor in a voltage doubling circuit, all circuit boards were built in the plugs on each end.

    I had ordered 132 strings, various colors of C6 and M5, $1229.80. The only way that many of us could use them, was to cut off the ends, build FWR circuits and attach back to the strings. (I built mine in empty plastic 35 mm roll film canistors)

    Paul was livid when he heard about the problem, and immediately offered to replace every string. Told us to go ahead and use them for 2008 and send them back in Jan 2009 for replacement. With the ends cut off!

    Paul bought some LOR controllers and flew to China in the fall 0f 2008, to show the engineers what their strings were doing.

    The factory made a new design, produced some prototypes to distribute, and I was one of the ones he chose to beta test the new design. All of us beta testers experienced problems, made voltage measurements etc at before and after failure.

    We went through 3 different sets of prototype strings before they finally designed something that would work with the LOR controllers.

    The replacement strings I received in 2009 are still working great. Paul did tell me that the new design added about 20% to their mfg cost, and the factory only made enough to replace Paul's order and then went back to their old design.

    Of course Paul never bought from them again, and returned to the ol' tried and true factory he had previously used.

    And that children, is todays history lesson regarding LED strings that use capacitors.
    John (The Mascot)
    www.tennholidays.com

    480 LOR Channels + 2 CCR + 8 Mighty Minis + 10 Rainbow Floods+ 1 vdrive and vflood, Lynx Express and over 40,000 LEDs

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    Space rented from Al SWood's Avatar
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    Default Re: Martha Stewart "Flicker Free" LED Strings

    I hear ya John, I already have my list made up for the CDI pre-sale of red and green strings I need for next year. The only reason I bought these was because of the light trade in deal and HD seems to be the only big box store to have red and green LEDs. I just hope the lights I have now don't give me any trouble this year. I don't have any Martha's out mostly the GE LEDs from Lowes.
    Shannon Wood
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