Handling SCR's outputs

Discussion in 'The Projects Forum' started by jj_alukkas, Jun 25, 2011.

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  1. jj_alukkas

    Thread Starter Distinguished Member

    Jan 8, 2009
    Hi all,

    Looking in my old stuffs, I found a Chinese rice light(serial set) circuit board in working condition. I found 2 PCR406 devices and expected it to be transistors and when I googled for datasheet, came to find that they were SCR's.. They control the pattern on the 2 lines of tiny bulbs. These 2 SCR's are controlled by a chip which has no id as its the usual Chinese black drop type covered custom chip. I checked out the datasheet and found the SCR's to handle 400v max and 800mA rating.. I'm new with SCR's, so could somebody help me how its different from transistors? I read abt it on Wikipedia and all, but what makes it more powerful over transistors? Also can I run a couple of led's on the output lines instead of those bulbs? I read its output is current limited. What voltage and current should I expect? I have made a sketch of details of all what I could find on the board.

    Thanks You.

  2. SgtWookie


    Jul 17, 2007
    SCR's are pretty well covered on this page in our E-book:
    Back up to the Schockley diode to get more of an intro.

    Unfortunately, the circuit that you have shown does not use a transformer to isolate from mains power; therefore it is not safe and we cannot discuss it on the forum.

    There is no way to make it safe without using a transformer to isolate it from mains power.
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    I'm afraid we can't help with this particular circuit, as it runs off the line with no isolation, making it very dangerous to use -
    We can give you a link to learn about SCR's - http://www.allaboutcircuits.com/vol_3/chpt_7/5.html
  4. jj_alukkas

    Thread Starter Distinguished Member

    Jan 8, 2009
    Hmm.. ok.. Anyway Thanks for the link.. gotta fix it myself!
  5. bertus


    Apr 5, 2008

    Please use an isolation transformer for safety.

    These pages from the EDUCYPEDIA will give you information on thyristors (SCR):

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