How many LEDs to a dimmer

Discussion in 'C-Bus Wired Hardware' started by l60mcm, Mar 24, 2012.

  1. l60mcm

    tobex

    Joined:
    Nov 3, 2006
    Messages:
    728
    Likes Received:
    0
    Location:
    Sydney, Australia
    Since they are a GU10 then measuring the capacitance would pose a few challenges. If they are running a switch mode power supply the circuit wont even kick in unless there is some kind of power applied. I will try and do the same thing when my meter arrives and see what happens when I pump 30V across the terminals.
     
    tobex, Mar 27, 2012
    #21
  2. l60mcm

    l60mcm

    Joined:
    Oct 5, 2010
    Messages:
    87
    Likes Received:
    0
    Location:
    UK
    like this i am still getting 0
     

    Attached Files:

    • 3.jpg
      3.jpg
      File size:
      106.6 KB
      Views:
      336
    l60mcm, Mar 27, 2012
    #22
  3. l60mcm

    tobex

    Joined:
    Nov 3, 2006
    Messages:
    728
    Likes Received:
    0
    Location:
    Sydney, Australia
    I think that GU10 is generally a huge pain. I dont think it is your fault.
     
    tobex, Mar 27, 2012
    #23
  4. l60mcm

    Newman

    Joined:
    Aug 3, 2004
    Messages:
    2,203
    Likes Received:
    0
    Location:
    Adelaide, South Australia
    That particular meter you are using looks like it cannot measure capacitance on the multimeter probes. You have to physically insert the capacitor into the two slots on the face of the meter labelled "Cx" (just above the "COM" terminal). You won't be able to measure the capacitance of the GU10 lamp using that meter unfortunately (unless you can poke the wires from the GU10 connector into those two slots). You will also most likely need the 400nF scale.

    A short circuit is much more likely. The resistance of the filament when cold is very low, rising as the current in the filament increases. If you measured an open circuit on a conventional halogen bulb then the most likely reason was a bad/incorrect contact.

    The capacitor of importance usually sits right across the front-end of the circuit inside the lamp for reducing conducted emissions, so it is before the switch-mode stage or even the rectification stage inside the lamp, generally making it trivial to measure with a capacitance meter. There are some exceptions.
     
    Newman, Mar 27, 2012
    #24
  5. l60mcm

    DarylMc

    Joined:
    Mar 24, 2006
    Messages:
    1,308
    Likes Received:
    49
    Location:
    Cleveland, QLD, Australia
    In that case you have no easy option other than consult the manufacturer.
    If they won't provide data you can understand why other led's may cost more.
    You have the option to run the gauntlet with an unknown product or pay for something which is supposed to work.
    Din rail dimmers aren't cheap.
    Pierlite Starburst for example, while expensive can do 6 lamps per channel on the leading edge dimmer or 36 lamps per channel on the universal dimmer so you have to look closely at the total cost.
    I'm sure there is many others but thats just one example of a lamp which provides specifications.
    The led's you have aren't terribly powerful and are going to give less light than a 50w halogen without question.
    Thanks for doing that test with the socket.
     
    DarylMc, Mar 27, 2012
    #25
  6. l60mcm

    DarylMc

    Joined:
    Mar 24, 2006
    Messages:
    1,308
    Likes Received:
    49
    Location:
    Cleveland, QLD, Australia
    Hi Newman
    I looked at that closely at that meter but it seems I missed it.
    There seems to be a socket for capacitance.
     
    DarylMc, Mar 27, 2012
    #26
  7. l60mcm

    alexdski

    Joined:
    May 17, 2011
    Messages:
    17
    Likes Received:
    2
    Location:
    UK
    Small (20W) incandesant load on each circuit.

    Without getting a calculator or multimeter out I've eliminated all flickering and genreal bad behaviour with my dimmable GU10 LEDS, (all bought here) by having at least one incandesant bulb on each circuit.

    For example, I have an L5508D1A with one one circuit that has 9 outputs. Using 9 of the 4W leds above caused two problems, flickering and a residual current build up that would blow the breaker.

    By putting one 20W incandesant (halogen) bulb on the circuit, so having 8 x 4W LEDS and 1 20W halogen I've got no residual current bulding up and flicker free dimming.

    I'm paying 16W for smoother operation but it's worth it with LEDS at this price.
     
    alexdski, Mar 27, 2012
    #27
  8. l60mcm

    tobex

    Joined:
    Nov 3, 2006
    Messages:
    728
    Likes Received:
    0
    Location:
    Sydney, Australia
    When you can no longer purchase MR16 halogens ...you might travel down this path all the same. However I wish to indicate that not all LED systems have this problem. This is largely associated with some of the first products on the market. As the LED market matures .... the designs will eliminate this problem. By using the appropriate driver from ACTEC I didnt have this issue. I personally dont have any issue with flickering with 7 GU10 x 10W in one channel on a dimmer.

    Other people have been really clever and used a relay channel with a dimmer channel. When it is switched off nothing is glowing.

    I personally will go down the X2 Capacitor road. For me that is a viable and custom solution for clients using the current technology. It demands a little more work but it is certain to satisfy the needs of many situations.

    Ok that is good to know. I saw that the lamp had capacitance on the output side and assumed that was part of the problem - but for the logical reasons your answer is more indicative.
     
    Last edited by a moderator: Mar 27, 2012
    tobex, Mar 27, 2012
    #28
  9. l60mcm

    DarylMc

    Joined:
    Mar 24, 2006
    Messages:
    1,308
    Likes Received:
    49
    Location:
    Cleveland, QLD, Australia
    Hi Alexdi
    I did notice the link to the particular lamp was saying "NOT to be used on the same Dimmer circuit with a non LED bulb."
    Don't know why.
     
    DarylMc, Mar 27, 2012
    #29
  10. l60mcm

    l60mcm

    Joined:
    Oct 5, 2010
    Messages:
    87
    Likes Received:
    0
    Location:
    UK
    I was just testing it in that slot as you posted your response. I have tried 2 different bulbs the picture with the lower number is the one I want to use do you reckon it is a reliable reading because it is so low
     

    Attached Files:

    • 4.JPG
      4.JPG
      File size:
      114.3 KB
      Views:
      344
    • 5.JPG
      5.JPG
      File size:
      106.7 KB
      Views:
      330
    l60mcm, Mar 27, 2012
    #30
  11. l60mcm

    Newman

    Joined:
    Aug 3, 2004
    Messages:
    2,203
    Likes Received:
    0
    Location:
    Adelaide, South Australia
    It is quite possible that there is no front-end capacitor fitted, and that is why the reading is so low. It's also unlikely that such a lamp would be EMC compliant so, illegality aside, you risk having interference with your TV and radio reception. I say this not to scare you, but to warn you of the possibility. It is possible to make EMC compliant LED downlights without EMC filter capacitors on the front-end but they are very rare. Generally speaking they can be minimised but not eliminated. With a reading that low, I would be sceptical.

    This is generally a feasible technique for removing flicker in the off-state and increasing dimmer stability. There are a few things to watch out for however:

    • Just because the light output is stable does not mean that the power delivery to the lamp is stable. It's quite possible that the light output looks OK but the dimmer channel is not stable in it's operation, and this can be destructive to the dimmer in the long-term.
    • Fitting a small incandescent load to the same circuit does not mean that you can ignore the capacitance limit for the leading edge dimmer channel. You still must abide by the 300nF limit, regardless of any additional incandescent loading. Ignoring this, even if the dimmer appears to be working fine, places a lot of stress on the leading edge dimmer.
    Crikey. That would make me nervous!
     
    Newman, Mar 27, 2012
    #31
  12. l60mcm

    l60mcm

    Joined:
    Oct 5, 2010
    Messages:
    87
    Likes Received:
    0
    Location:
    UK
    Thanks for you help how can I test if they comply. Is says on their site here ROHS and CE Approved I know this is not the same thing.
     
    Last edited by a moderator: Mar 28, 2012
    l60mcm, Mar 27, 2012
    #32
  13. l60mcm

    tobex

    Joined:
    Nov 3, 2006
    Messages:
    728
    Likes Received:
    0
    Location:
    Sydney, Australia
    ROHS means without lead or toxic metals.
     
    tobex, Mar 27, 2012
    #33
  14. l60mcm

    Newman

    Joined:
    Aug 3, 2004
    Messages:
    2,203
    Likes Received:
    0
    Location:
    Adelaide, South Australia
    There is no practical way a typical person can test EMC performance. It requires access to an electronics laboratory with the necessary test equipment.
     
    Newman, Mar 28, 2012
    #34
  15. l60mcm

    alexdski

    Joined:
    May 17, 2011
    Messages:
    17
    Likes Received:
    2
    Location:
    UK
    Or an old AM tranny??
     
    alexdski, Mar 28, 2012
    #35
Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.