Shift Register not working

Discussion in 'General Electronics Chat' started by Raul Junc, May 19, 2015.

  1. Raul Junc

    Thread Starter New Member

    May 19, 2015
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    0
    Hello I have a problem with the shift register. When I turn on the device sometimes I get random data already(ex QB, QC is high) this is the case when the shift register works as expected, but when I turn on the device and get from start every Q output as low, the shift is not working at all(can't insert 1's). What is even more weird is that when I already have something in it if I shift 0's till all are low, again is not working at all, can't insert other 1's. I connected pin 10(SRCLR) to +

    The circuit used is SN74HC595N
    Here is a link to the schematics i used: http://html.alldatasheet.com/html-pdf/27939/TI/SN74HC595N/24/1/SN74HC595N.html
     
  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Can you post a schematic of your circuit? Without it, we can't see where the problem might be.

    ak
     
  3. MrChips

    Moderator

    Oct 2, 2009
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    If you are creating a PRNG, then a register with all 0's will remain in that state.
    You have to ensure that you never have all 0's even on power up.
     
  4. Raul Junc

    Thread Starter New Member

    May 19, 2015
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    upload_2015-5-19_17-41-0.png
    Hope it helps.
     
  5. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Those are images of the chip. I'm asking about *your* circuit, not the datasheet. The connections to the chip the other parts around it. What is the circuit, and what is its function? What are you trying to achieve?

    ak
     
  6. Raul Junc

    Thread Starter New Member

    May 19, 2015
    3
    0
    upload_2015-5-19_19-22-0.png
    I just want to make a shift register, see that it works like I expected, I don't have anything connected to it. Here is a picture with what i have so far.
     
  7. MrChips

    Moderator

    Oct 2, 2009
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    You cannot drive LEDs directly from CMOS logic and get reliable operation.
     
  8. dl324

    Distinguished Member

    Mar 30, 2015
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    Why won't you post a schematic? People want to help you, but asking someone to trace your breadboard to make a schematic is asking for too much...
     
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