Announcement

Collapse
No announcement yet.

Eiko t8 led typeB

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    #31
    Originally posted by gar View Post
    180423-1627 EDT

    Mparn:

    The probable reason the T12s never flashed was need for greater energy, and possibly less coupling of transient energy.

    .
    Thank you for all your help today. Could this lead to bigger problems down the road?

    Comment


      #32
      I suggest you look at IEEE 1789-2015 paper.

      I suspect your problems have nothing to do with wiring, loads, or shared neutrals. Might prove interesting to see how many others notice this problem. Some are much more sensitive. I am....probably borderline epileptic!

      This isn’t an unknown problem and why I advised trusted name. Also mentioned a driver would do better. Problem is most won’t work on 277.

      Really hoping problem is some simple/stupid wiring issue. But do be aware some are suggesting there is a health risk. That is not a place you want to be with children involved.

      Not trying to worry you. Just saying it might be time to slow down and evaluate things.

      Comment


        #33
        Gotcha thanks, I have tried 2 different brands (one being phillips) with the same results. This is a one time flicker on a lamp or few lamps when others are powered on. We've been monitoring the lamps daily for any flickering or strobing. No one seems to find evidence of either.
        Last edited by Mparn; 04-23-18, 07:08 PM.

        Comment


          #34
          180423-1946 EDT

          [COLOR=#000000]Russs57:

          The [/COLOR][COLOR=#000000]IEEE 1789-2015 has nothing to do with the problem that Mparn was questioning. Mparn described a single shot transient event. [/COLOR][COLOR=#000000]IEEE 1789-2015 is concerned with a continuous steady state modulation of light intensity. Should this be of concern? Yes. But it is not what the original post was about.

          . [/COLOR]

          Comment


            #35
            180423-1958 EDT

            Mparn:

            If the single shot flicker does not bother anyone, then I would do nothing about it. I doubt that it is a resistive leakage problem.

            The [COLOR=#000000]IEEE 1789-2015 brings up a much bigger and different concern. LEDs designed to provide some approximation of visible white or other color light generally are a blue or UV LED used to excite a phosphor(s) in the visible spectrum. These phosphors generally have moderate time constants of intensity decay. Thus, a square wave drive of the LED emitter that produces a square wave of blue or UV light may have a much more averaged visible light output. The time constants of the different colors from the LED phosphors may not and probably are not the same. Thus, the percentage of flicker from each color may differ.

            For other reasons it would be good to drive LED chips from DC.

            . [/COLOR]
            .
            Last edited by gar; 04-23-18, 08:19 PM.

            Comment


              #36
              I noticed a weak switch today in one of the classrooms. If i held the switch in the middle, the other series would get more of a random flicker. Could it be several of the switches are going bad? It even happened if I would just push in on the switch

              Comment


                #37
                190426-2032 EDT

                Mparn:

                With inductance in a circuit and current flowing the opening of the circuit can easily produce thousands of volts to initiate a spark or arc across the opening element. This how an old automotive ignition coil works.

                To test the sensitivity of electronic circuits to transient noise I have simply rapidly oscillated a plug to a two bulb 8 ft Slimline fixture.

                Will arcing of a set of switch contacts in some fashion couple enough energy into a turned off LED circuit to momentarily flicker the LED? I don't know. But you may have demonstrated that it does.

                .

                Comment


                  #38
                  Originally posted by gar View Post
                  190426-2032 EDT

                  Mparn:

                  With inductance in a circuit and current flowing the opening of the circuit can easily produce thousands of volts to initiate a spark or arc across the opening element. This how an old automotive ignition coil works.

                  To test the sensitivity of electronic circuits to transient noise I have simply rapidly oscillated a plug to a two bulb 8 ft Slimline fixture.

                  Will arcing of a set of switch contacts in some fashion couple enough energy into a turned off LED circuit to momentarily flicker the LED? I don't know. But you may have demonstrated that it does.

                  .
                  Thanks, the flicker happens in the circuit that is already on, when the other is turned on.

                  Comment


                    #39
                    180427-1005 EDT

                    Mparn:

                    At this point you need to define some words and run some independent experiments.

                    Flicker could means a number of different things. Is it a single shot event? Does it means 120 Hz ripple on light intensity? Not in your case, but it did in [COLOR=#000000]Russs57's comment. Does it mean an increase in intensity, or a decrease? Is it a short duration oscillation in intensity? Or etc.

                    [/COLOR]Consider two 120 V switched 100 W bulbs fed from the same phase and sharing a common neutral of 10 ohms. A cold 100 W 120 V incandescent bulb is about 10 ohms, and hot about 144 ohms. With one bulb on its voltage is about 120*144/154 = 112 V. You would see a brightness difference in the bulb compared to a circuit with a much lower neutral resistance.

                    I have selected the bulb size and neutral resistance such that you can easily experiment. 100 W incandescent bulbs are still around, and a moderately stable resistance at 1 or 2 A and somewhat near 10 ohms is the resistance of a 1500 W space heater.

                    At the instant the second bulb turns on the voltage across the two bulbs is about 120*10/10 = 60 V. Actually a little less because you have 144 ohms shunting 10 ohms, or 9.35 ohms. So you will see a short time flicker in the dimming direction of the initially on bulb.

                    Now suppose the two bulbs are supplied from opposite phases. The 10 ohm neutral initially has a voltage drop of 120*10/154 = 7.8 V with one bulb on. At the instant that the second bulb is turned on two opposing currents exist in the neutral. Doing the math just after the second bulb is turned on I get a voltage drop across the 10 ohm resistor of about 54 V. This is in a direction to add voltage to the initially on bulb so that the already on bulb sees about 120 + 54 = 174 V. Thus, the already on bulb brightness momentarily increases a lot, bright flash.

                    When the turning on bulb reaches its high resistance the 10 ohm resistance has a voltage drop of about 0 volts, canceling currents thru the neutral, and the initially on bulb is slightly brighter than when it was the only load. You may not detect this.

                    The above is a suggested experiment that I have not played with but may illustrate how neutral impedance can affect components in a circuit.

                    LEDs have ballasts (power supplies) that may be pretty much like an uncharged capacitor at their input before turn on. Connecting an electronically ballasted LED at a voltage peak and large peak currents may flow.

                    .

                    Comment


                      #40
                      Originally posted by gar View Post
                      180427-1005 EDT

                      Mparn:

                      At this point you need to define some words and run some independent experiments.

                      Flicker could means a number of different things. Is it a single shot event? Does it means 120 Hz ripple on light intensity? Not in your case, but it did in [COLOR=#000000]Russs57's comment. Does it mean an increase in intensity, or a decrease? Is it a short duration oscillation in intensity? Or etc.

                      [/COLOR]Consider two 120 V switched 100 W bulbs fed from the same phase and sharing a common neutral of 10 ohms. A cold 100 W 120 V incandescent bulb is about 10 ohms, and hot about 144 ohms. With one bulb on its voltage is about 120*144/154 = 112 V. You would see a brightness difference in the bulb compared to a circuit with a much lower neutral resistance.

                      I have selected the bulb size and neutral resistance such that you can easily experiment. 100 W incandescent bulbs are still around, and a moderately stable resistance at 1 or 2 A and somewhat near 10 ohms is the resistance of a 1500 W space heater.

                      At the instant the second bulb turns on the voltage across the two bulbs is about 120*10/10 = 60 V. Actually a little less because you have 144 ohms shunting 10 ohms, or 9.35 ohms. So you will see a short time flicker in the dimming direction of the initially on bulb.

                      Now suppose the two bulbs are supplied from opposite phases. The 10 ohm neutral initially has a voltage drop of 120*10/154 = 7.8 V with one bulb on. At the instant that the second bulb is turned on two opposing currents exist in the neutral. Doing the math just after the second bulb is turned on I get a voltage drop across the 10 ohm resistor of about 54 V. This is in a direction to add voltage to the initially on bulb so that the already on bulb sees about 120 + 54 = 174 V. Thus, the already on bulb brightness momentarily increases a lot, bright flash.

                      When the turning on bulb reaches its high resistance the 10 ohm resistance has a voltage drop of about 0 volts, canceling currents thru the neutral, and the initially on bulb is slightly brighter than when it was the only load. You may not detect this.

                      The above is a suggested experiment that I have not played with but may illustrate how neutral impedance can affect components in a circuit.

                      LEDs have ballasts (power supplies) that may be pretty much like an uncharged capacitor at their input before turn on. Connecting an electronically ballasted LED at a voltage peak and large peak currents may flow.
                      Gar,

                      Thank you for all your help. Although you are way over my head, you have explained it to where I am able to understand. By "flicker" I mean, a single shot, one time, where the light dims or goes out. It happens really fast but you are still able to see it. You have to actually study it to see that it's dimming and not getting brighter.
                      Last edited by GoldDigger; 04-27-18, 06:32 PM. Reason: fix /QUOTE tag

                      Comment


                        #41
                        180427-2131 EDT

                        Mparn:

                        My two bulb experiment is not as good as I would like. The high current pulse generated by randomly turning on an incandescent (I used 75 W for convenience) does not have an adequately high probability of having its maximum value and longest duration as compared with a controlled turn on at the voltage peak. I could barely detect the transient pulse compared to the steady state change.

                        For an illustration of incandescent turn on current see my photos P1 thru P4 at http://beta-a2.com/EE-photos.html .

                        In doing this experiment the bulb being turned on should be totally out of view. Do not look directly at the always on bulb. Shine it on a wall or use something to greatly attenuate the brightness.

                        Do not view what I am describing as over your head. Think about it and ask any questions. You seem to have a great interest for looking into why things you see occur.

                        .

                        Comment


                          #42
                          180428-1146 EDT

                          Mparn:

                          I would like you to run an experimebt if you can.

                          I took my only LED fixture, a 4 ft twin tube Costco shop light, and with a Powerstat (variac) adjusted the input voltage from 70 to 140 V with a GE light meter monitoring the light intrnsity and saw virtually no intenity variation.

                          Do you have any way to change the AC sine wave voltage to one of your fixtures? If so, then even a visual observation may tell us whether the light output is particularly sensitive to voltage.

                          In contrast I can take a Cree screw-in 9.5 W bulb and get good dimming control with a variable sine wave voltage source.

                          .

                          Comment


                            #43
                            i recommend trying the new led's in various parts of the building's for a period of time (honestly i would test for a year before replacing that many) before replacing everything with LED, there has recently been an article series in EC&M magazine about ground planes for LED drivers that talks about some of the issues coming up with LED's especially in older facilities. i would think you would have decent bonding throughout the buildings but i would test before committing to all LED. i have seen several facilities that have kept replacing LED's and i suspect it may be related to the issue discussed in the articles in EC&M, they were older facilities and not very well wired to begin with.

                            Comment


                              #44
                              i'm not finding anyone else addressing it in this forum, but there was discussion over concern of 277v at the tombstones, don't most fixtures like the op currently has have lamp start voltages of several hundred volts at the tombstones? when you install or remove a lamp on an energized fixture you are exposed to that voltage, your exposed when you remove because you can easily disconnect and accidentally reconnect. or is the secondary of most ballasts not grounded?

                              Comment


                                #45
                                Our building were built in 1988 and 1999. Thanks for the info on the magazine, I'll look into that.

                                Kinexis, are you concerned with 277 at the sockets?

                                Comment

                                Working...
                                X