timing circuit

Discussion in 'General Electronics Chat' started by simf14, Dec 3, 2010.

  1. simf14

    Thread Starter Active Member

    Jul 27, 2007
    43
    0
    Hello and thank you!

    I have a simple timing circuit for a heater element that is adjustable from 1-7 seconds by a 250K pot. (the less resistance on the pot the shorter the time.) I would like to change the timing range to around .25-2 seconds or so.

    Could someone look at the manufacture's circuit drawing .jpg and help me with which resistor(s) would be the proper one to change? Would it be the 47K ohm resistor? I can experiment with the correct ohms just don't want to wreck anything. Thank you so much!
     
    Last edited: Dec 3, 2010
  2. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
    90
    The 47k sets the minimum time along with the 10uF timing capacitor. Lowering the value of the capacitor will shorten the time. 2.2uF should get you close. This should be a better quality low leakage capacitor.
     
  3. simf14

    Thread Starter Active Member

    Jul 27, 2007
    43
    0
    thank you....should i keep the 47k the same?
     
  4. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
    90
    See how it is with it in there. You can't go too low, you'll make the C458 transistor angry.
     
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