Timing Components ID

Discussion in 'The Projects Forum' started by JDR04, Dec 18, 2013.

  1. JDR04

    Thread Starter Active Member

    May 5, 2011
    339
    4
    Hi eveyone, bought this IR detector from EBAY and have tested it. So far it does the job I need it for.

    I would however like to reduce the "on time period" from 20 seconds to about 5 seconds but dont know which components I should change. At a guess I think it would be a resistor or capacitor, maybe both??

    Does anybody have a schematic for this device by any chance or, can you suggest how I would go about identifying the correct parts.

    Heres a link to it on EBAY.

    http://www.ebay.co.uk/itm/Mini-Port...Equipment_ET&hash=item35ccda96c2#ht_642wt_932

    Unfortunately the IC is unmarked so I'm not able to ID that either.

    I have attached photos of it hoping they help in some way.

    Thanks a lot - JDR04
     
    Last edited: Dec 18, 2013
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,986
    745
    All i can suggest is put a DVM across each capacitor in turn and see which one varies the voltage with the time.
     
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  3. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    It's not a 555 timer as pin 8 is +pwr and pin 5 is gnd. That also rules out most dual opamps whoich would have been my next guess.

    Re which is the timing cap, I would try C4 on the top of the PCB which seems to attach to pins 3 and 4.
     
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  4. JDR04

    Thread Starter Active Member

    May 5, 2011
    339
    4
    Thanks to THE RB. I'll give your suggestions a try and post the results here later.
     
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