Need to use 74HC14 IC, not 40106B

Discussion in 'The Projects Forum' started by doug08, May 21, 2012.

  1. doug08

    Thread Starter Member

    Jan 30, 2011
    153
    2
    In the circuit below. I already made a voltage divider to supply 6V to pin 14, instead of the 12-13.8V supply. All other 12v connections remain the same as the schematic. I also replaced the 1k resistor from the collector of Q2 with a 2.2K. I left the 680K as is, but thinking I should raise that to 1.2M. Any ideas? It works, but not right because the resistor values are not correct. I do have 6V at pin 14 when the circuit is connected and running. I used a 2n3904 for Q2, a 2n5961 for Q1, and a TIP 120 for Q3

    Thanks.

    [​IMG]
     
  2. mcasale

    Member

    Jul 18, 2011
    210
    12
    So, exactly what are you trying to do here? It looks like you are trying to amplify SOMETHING from the pickup and have it turn on a bunch of LEDs.
     
  3. MrChips

    Moderator

    Oct 2, 2009
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    I presume that this is a timing strobe light.

    Why bother use a 7414 or 40106. This is simply two inverter stages with an integrator in between?

    I would replace this with two transistors.
     
  4. doug08

    Thread Starter Member

    Jan 30, 2011
    153
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    Yes, it is a timing light circuit, and I already made it. So I would like to use the 7414 IC. If you were going to use the 7414 instead, what would YOU do besides adjusting the Vcc to 6v?

    Thanks
     
  5. MrChips

    Moderator

    Oct 2, 2009
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    Why did you switch from 40106 to 74HC14?
     
  6. wayneh

    Expert

    Sep 9, 2010
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    Why? Why not use the circuit offered in the diagram?
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    Use 5v for the Vcc instead of 6v. You can get a 5.1 Zener at a Radio Shack store.
     
  8. MrChips

    Moderator

    Oct 2, 2009
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    You could also use a 4049 at 12V.
     
  9. doug08

    Thread Starter Member

    Jan 30, 2011
    153
    2
    All I had was a 74hc14, otherwise I would have used the 40106B. So all I should worry about is just the Vcc? leave everything else as shown in the schematic? Put back the 1K resistor?
     
  10. MrChips

    Moderator

    Oct 2, 2009
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    This might be a silly question, but how difficult is it to lay your hands on a 4049, 4069, 40106, 4584?
     
  11. MrChips

    Moderator

    Oct 2, 2009
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    Oops... 4049 has wrong pinouts.
     
  12. doug08

    Thread Starter Member

    Jan 30, 2011
    153
    2
    VERY hard to get things where I am located. I "May" have a 4069 ic. That is a drop in replacement? Pinout the same as the 40106B?

    Thanks.
     
  13. MrChips

    Moderator

    Oct 2, 2009
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    The 40106 and 4584 are inverters with Schmitt triggers.
    4069 is a plain inverter. In your circuit it should make no difference. Pinouts are the same.
    They will all run at 12V.
     
  14. doug08

    Thread Starter Member

    Jan 30, 2011
    153
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    I do have 4069's. I will de-solder the 74hc14, and install the 4069, and put back the 1K resistor instead of the 2.2K.

    Thanks
     
  15. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    If I had to use 74HC14, I would do it like this.
    You may have to play with the value of the 680k to get the desired pulse width.
    You said the PNP is 2N3904. That is an NPN. Use 2N3906.
     
  16. doug08

    Thread Starter Member

    Jan 30, 2011
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    2
    I did use a 2n3906, not a 3904.
     
  17. doug08

    Thread Starter Member

    Jan 30, 2011
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    Works, but the light does not show the timing marks. I tried replacing the 680K with a 1M pot. No difference. How do I adjust it?
     
  18. MrChips

    Moderator

    Oct 2, 2009
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    Are the LEDs bright enough? Can you see the LEDs flash with fairly good intensity.
    Are you doing this in bright sunshine or in the shade?
    Try doing this in the garage/shade/dark/cloak over your head and engine.
    Mark the timing marks with white chalk.
    You should see the flywheel stationary (synchronized with the ignition timing).
     
  19. doug08

    Thread Starter Member

    Jan 30, 2011
    153
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    Nice bright led strobe. Does not show the timing mark. I made other types before which worked fine. If I add to the 6.8nF cap, it makes the led brighter.
     
  20. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    The 680k and 6.8nF cap are part of a pulse stretcher. Make the time constant (R*C) larger, and the pulse will get wider, i.e., your LEDs will stay on longer. If you make it too long, the timing mark will appear smeared, getting worse as the RPMs increase.

    What is the inductive pickup sensing? Are you sure it's mechanically aligned properly?
     
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