230v ac phase dimmer and zero crossing circuit

Discussion in 'The Projects Forum' started by Veer Bhadra, Jul 31, 2018.

  1. Veer Bhadra

    Thread Starter New Member

    Jul 31, 2018
    3
    0
    Hi everyone!

    In my zero crossing circuit i have connected two 30k resistors each rated 2W . They are producing more than 60 degree centigrade heat .. I experimented with 1/2 watt and 1watt also same heat i'm observing.. How can i reduce the heat ?.
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    16,210
    4,755
    Use a small transformer.
    Max.
     
  3. ebp

    Well-Known Member

    Feb 8, 2018
    2,056
    726
    A 4N25 is a very bad choice for this application. It's current transfer ratio is low and it is characterized at 10 mA IRED current. The thing really should have disappeared from the market 20 years ago.

    Double or triple the pullup resistor on the output of the coupler and get a better coupler. Even a 4N35 is a big improvement and still very inexpensive. There are couplers that are well-specified with sub-milliampere drive for the IRED, though some are a bit more expensive.
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
    16,210
    4,755
    1/2 watt resistors is not high enough, see Fairchild AN-3006.
    Max.
     
  5. Veer Bhadra

    Thread Starter New Member

    Jul 31, 2018
    3
    0
    Thanks for reply
    Here I'm not using any transformer.. I'm directly connected two power resistors each of 33k rating 2W to phase and neutral lines before bridge diode. .. These two resistors are dissipating more than 60 degree centigrade of heat .... Do we have any solution so that we can reduce heat?
     
  6. Veer Bhadra

    Thread Starter New Member

    Jul 31, 2018
    3
    0
    Thanks for your reply
    I'm facing problem in resistor side they are dissipating too much heat.....I'm directly connected two power resistors each of 33k rating 2W to phase and neutral lines before bridge diode. .. These two resistors are dissipating more than 60 degree centigrade of heat .... Do we have any solution so that we can reduce heat?
     
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