Timing Components ID

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

  1. JDR04

    Thread Starter Active Member

    May 5, 2011
    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.


    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

    AAC Fanatic!

    Jun 22, 2012
    All i can suggest is put a DVM across each capacitor in turn and see which one varies the voltage with the time.
    JDR04 and Bernard like this.
  3. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    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.
    JDR04 likes this.
  4. JDR04

    Thread Starter Active Member

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