active-low circuit problem

Discussion in 'General Electronics Chat' started by Prestyman, Jan 14, 2009.

  1. Prestyman

    Thread Starter Member

    Nov 14, 2008
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    I'm returned to a project that I thought I had solved, but has turned into a bit of a headache. Hopefully someone can help.

    I have a module with 8 pins that are active-low. I also have a push-button triggering unit with eight pins that each go high when the corresponding button is pushed.

    What is the easiest (in terms of soldering parts) way to get the two modules to "talk" to each other.

    FYI, my original attempt was 8 transistors, and the necessary resistsors, but that's 40 solder points, which is lot of work if I decided to start making a number of these gizmo's for fellow entertainers.

    Is there a better way?

    Thanks,
    Clinton
    <SNIP>
     
    Last edited by a moderator: Jul 10, 2010
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Use two quad NOT gate chips to invert the outputs of the switches.
     
  3. Prestyman

    Thread Starter Member

    Nov 14, 2008
    29
    0
    Is it really that easy? Just the Quad NOT gates?

    Nothing else is required?
     
  4. Prestyman

    Thread Starter Member

    Nov 14, 2008
    29
    0
    I'm having a heck of a time finding quad NOT gate chips. Does anyone have a part number?
     
  5. silvrstring

    Active Member

    Mar 27, 2008
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  6. Prestyman

    Thread Starter Member

    Nov 14, 2008
    29
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    Thanks, but those all appear to be hex inverters. I wanted quad.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    You can use hex inverters; just don't use two of the inverters on each IC.

    74xx series are TTL logic. They need to have 4.5v to 5.5v as a supply voltage; they won't work properly if your power supply is above or below that.

    You might use 4000 series CMOS logic IC's. They will operate using voltages from 3v to 16v. Their disadvantages are high static sensitivity and low output current.
    4069's are hex inverters. 40106's are hex inverting Schmitt triggers.
    4093's are quad Schmitt trigger 2-input NAND gates. You can use NAND gates as inverters if you wire the two inputs to a gate together.
    Note that ALL unused inputs for 4000 series CMOS gates MUST be tied to either ground or Vdd (V+)
     
  8. Prestyman

    Thread Starter Member

    Nov 14, 2008
    29
    0
    Thanks for the detailed explanaton. It loks like by the time I wire the inputs of the NAND gates together, tie the unused pins to ground, and supply power to the ICs, I'm back to as many solder points as using the transistors. Not quite, but close.

    Maybe the answer is to pay to have it done for me. Are there services where someone can supply a printed board with the necessary surface-mounted components already soldered? Whom would you suggest?

    Thanks,
    Clinton
     
  9. Prestyman

    Thread Starter Member

    Nov 14, 2008
    29
    0
    Still looking for a supplier of printed boards with surface-mounted components. Any suggestions?

    ~ Clinton
     
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