EMI issue with LED DRIVER

Discussion in 'General Electronics Chat' started by kcbhojwani, Jun 11, 2016.

  1. kcbhojwani

    Thread Starter New Member

    Jun 11, 2016
    5
    0
    Hi All,

    I am having an issue which i have been struggling with for about a year. I am not very technical when it comes to EMI and LED and i have been searching everywhere and have even had long long phone conversations with tech support of different companies. Recently we pinpointed the problem and searches have led me to this forum, where i hope i can get some assistance.

    The problem i am having is with the following products:
    -LED panel 48w
    -LED Driver model JY-48W (Input 85-265AC 50/60, output 48W, DC38v -1.1a)
    -Checkpoint EAS system operating at 8.2Mhz.

    I have a retail outlet with over 100 LED panels, each using the above mentioned driver. We also have an anti-theft alarm system installed at the entrance. this alarm system does not function well, and not matter what setting we put it at, it will not detect an alamr tag that is more than 25cm away, while the range is supposed to be 1.5 meters (approx)

    After a lot of testing we finally figured out that even if an LED light at the other corner of the building is turned on, there is an interference with the alarm system. I read online that this may be caused by the switching of current from AC to DC, so we removed the LED DRIVERS that were close to the alarm system, but this did not fix the problem as the alarm antennas were still detecting interference. they told me that because this is a metal structure, the beams are 'carrying' this interference all throughout the building. Mind you that the antenna works perfectly outside the building or with all the lights turned off.

    Since a large investment has been made in both the alarm system and the LED panels, i was hoping there may be a solution to this problem, without having to replace either product.

    we even tested the LED DRIVER on its own, without plugging in the LED PANEL to it, but this did not give out as much EMI as when you DO plug the PANEL into the DRIVER. i am not sure if this is because there is no connection to the drive and thus the DRIVER does not convert the current or if the problem lies with the actual PANEL. i opened the LED PANEL to see if there was any circuitry inside, but only found 4 strips of LEDs along the sides. no boards or anything else.

    Does anyone know of any Large AC-DC converters that i can place outside the building for multiple LED PANELS and dismiss the individual DRIVERS that each LED PANEL has? will this solve the problem?

    Any help will be appriciated.
    Thank you in advance!

    Regards,
    Keshav
     
  2. andrewmm

    Active Member

    Feb 25, 2011
    30
    6
    A world of pain Ah..

    So the leds.
    normaly you can not just connect DC to them, they need a current limited supply.
    It could be the current limiting supply is in the led panel, or more likely in the external controler..

    so putting DC direct on to the leds is probably not a good idea.

    The current limit on the leds, is normally done by switching them on / off fast. Many KHz . That could also be whats causing the alarm problem, as it sounds like its a door alarm, one of those walk through an the tag sets off the alarm.
    Unfortunately, these alarms also work at a radio frequency in the same range.

    if you can find some links to the parts we might be able to help,
    but remotely sorry , don't hold out much hope
     
  3. RichardO

    Well-Known Member

    May 4, 2013
    1,235
    384
    I wonder if the interference is coming in on the power line. You could try powering the checkpoint system through a power line filter. Do a search on "power line filter" to see what is available.

    You might be able to find a unit that has a power cord and an outlet. Some outlet strips also have power line filtering built in. Either way, the test is quick and fairly inexpensive.
     
  4. dannyf

    Well-Known Member

    Sep 13, 2015
    1,782
    360
    those led drivers are essentially smps configured as constant current driver. without a load, they bare oscillate.

    You can get a better driver or do better shielding, particularly at the frequencies of the alarm / rf sensors.
     
  5. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,287
    1,252
    How far away from the panels are the drivers?
     
  6. Techno Tronix

    Member

    Jan 10, 2015
    140
    10
    LED lighting must be more aggressive to meet EMI, because driver circuits for the LED products operate at higher frequencies than the older incandescent bulbs (which operate directly off of the 50/60Hz line volt- age).
     
  7. kcbhojwani

    Thread Starter New Member

    Jun 11, 2016
    5
    0
    Hi Everyone. Sorry for the delay in responding. i am currently travelling and have limited access to this forum. I will try to answer some questions/ provide more info to everyone who is trying to help me. thanks again for that!

    Andrewmm: thanks for the post. i will discard the option of putting DC on the leds without the driver. unfortunately, i do not have links to the parts, but i have uploaded some images which may help.

    RichardO: The antenna actually has a filter in the powerline. it comes with one build in. it works on 220v while the led panels work on 110v

    DannyF: i was going to try wrapping foil tightly around each of the LED drivers. do you think that could work, or would i get a problem with the driver overheating or such?

    Ronv: the driver are placed right on top of the panels. should i try moving them away from the panels?
    driver.jpg
    panel.jpg
     
  8. crutschow

    Expert

    Mar 14, 2008
    13,003
    3,232
    It may be radiating from the power line feeding the LEDs.
    The power line can make a good antenna.
    I would try a good common-mode type power line filter for the LED power supply to see if that helps.
     
  9. kcbhojwani

    Thread Starter New Member

    Jun 11, 2016
    5
    0
    Hi crutshow, thanks for your post. I did a google search on common-mode power line filters and saw a whole bunch of technical data and images that went way above my head. i also did an amazon search to see look for a common-mode powerline filter. most of the results were like the following item:
    https://www.amazon.com/TDK-ACM2012-...&sr=8-6&keywords=common-mode+powerline+filter

    is this the correct filter you were talking about? and how and where would i install them if they were?

    thanks in advance!
     
  10. dannyf

    Well-Known Member

    Sep 13, 2015
    1,782
    360
    The PS seems to have a metal casing so wrapping it in metal foil provides marginal help. You may try grounding it - make sure there case is isolated.

    A common mode filer can be a little ferrit code and the power lines wrap around it a few loops.

    Or you can buy power cables wiithbthe filter built in, like laptop supply cables.
     
  11. dannyf

    Well-Known Member

    Sep 13, 2015
    1,782
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    It is easy to see if the PS is thee problem if you have a proper PS. Just power your LED. Panel with a proper PS and see if the interference persists.
     
  12. kcbhojwani

    Thread Starter New Member

    Jun 11, 2016
    5
    0
    Hi Danny,

    i assume by PS you mean the LED Driver, correct?
    I will try and get some ferite cores and see if i can wrap the electrical wires that BEFORE the Led driver. is that the right way?
    I am not sure about buying power cords, as i do not know how they are connected in the ceiling. there may be power outlets in the ceiling to which multiple drivers may be connected. if so, do we place the filter before each power outlet?

    the structure is basically a huge metal warehouse converted into a retail space and that is wht i am not sure what is going on in the ceiling between the drop ceiling and the metal structrure
     
  13. kcbhojwani

    Thread Starter New Member

    Jun 11, 2016
    5
    0
    Also, we have about 150 LED panels already installed!
     
  14. crutschow

    Expert

    Mar 14, 2008
    13,003
    3,232
    I would put CM filters both at the input and the output of each LED driver circuit.
    Wrappin a few turns of the wire pairs through a ferrite core should help, one core for the input and one for the output.
    Can you try it on just one panel to see if it helps?
     
  15. RichardO

    Well-Known Member

    May 4, 2013
    1,235
    384
    This is a good idea. To see if this helps it is best to turn off as many of the 150 panels as you can. Good luck!
     
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