Ram circuit help.

Discussion in 'Homework Help' started by GTeclips, Feb 18, 2012.

  1. GTeclips

    Thread Starter Member

    Feb 18, 2012
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    Hello, I have recently be getting into bread boarding.

    This doesn't have anything to do with homework, but I'm just a little annoyed.

    I'm trying to make an extremely simple ram circuit using the NTE4013b Dual d flip-flop IC, but I'm having a problem with it! No matter whether the data input is high or low, when I trigger the clock, both Q and Q' outputs are high. And as far as I know, that is impossible. I don't know whether I have wired it wrong or maybe have fried the chip or maybe just don't properly understand the IC.

    Can anyone help me out please!
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
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    Post your circuit here for us to see what technique you are using.

    hgmjr
     
  3. justtrying

    Active Member

    Mar 9, 2011
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    might be a bad chip, but look at the truth table from the specs. What have you done with the SET/RESET pins? From what I gather if you are using clock to trigger, they should be grounded, never leave them floating as they will be seen as high or in no-mans land. If seen as high, than the output is exactly what you have, 1 at both Q and Q'. Check the circuit, the wiring and get the DVM and start checking voltage levels.
     
  4. GTeclips

    Thread Starter Member

    Feb 18, 2012
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    Edit: Oh, ok thank you! I will try this now!
     
  5. GTeclips

    Thread Starter Member

    Feb 18, 2012
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    Well, that solved the impossible output issues.

    But now its doing very strange things. No matter if I have the d inputs low or high when I trigger the clock, they don't switch, and sometimes they will just randomly switch even when I haven't trigger the clock! Its almost like its getting interference from somewhere!

    Edit: Just thought I'd add that I don't have a voltmeter.
     
    Last edited: Feb 18, 2012
  6. justtrying

    Active Member

    Mar 9, 2011
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    what are you using for the clock? and you really should get a voltmeter if you plan to work with more projects like this ;)
     
  7. GTeclips

    Thread Starter Member

    Feb 18, 2012
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    Well I'm using a 9v Duracell battery, and to trigger the clock, I'm simply connecting and disconnecting a wire.
     
  8. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,365
    Having both Q and Q' high is not impossible in an R-S flip-flop. The problem is in the semantics, i.e. the labels Q and Q'. Instead call these Q and P if you wish.
     
  9. justtrying

    Active Member

    Mar 9, 2011
    329
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    It would be good if you posted the schematic.

    there are usually bouncing problems to be taken care of as well, the flipflop is not triggered properly as you use wire to control clock input. What you need is to implement a debouncer. This is a must when using any kind of switch with FFs.

    here two types are described, usually the NAND SR is implemented http://www.eetimes.com/discussion/break-points/4024956/Solving-Switch-Bounce-Problems
     
  10. GTeclips

    Thread Starter Member

    Feb 18, 2012
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    First off, would it be best to take a picture of my circuit and post it, or use a diagramming program?

    Second, I was wondering, could it be possible that 9v is to much for any of the inputs?

    Lastly, I'm not sure I have the elements to make a debouncer. I do not have a SR latch, but I do have a NAND IC and a Hex Inverter IC.
     
  11. justtrying

    Active Member

    Mar 9, 2011
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    Diagram helps the most. For supply voltages check the spec sheet. The debouncer is made of 2 nand gates and some resistors (check the link I gave or just do a search). It may or may not be a problem but bouncing switch is an unwanted variable in troubleshooting digital circuits.
     
  12. GTeclips

    Thread Starter Member

    Feb 18, 2012
    96
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    Ok, well as far as I can see from the data sheet, the IC doesn't require any resistor for a 9v power supply. I will see if I can put together a debouncer.

    Do you know any good diagramming software?
     
  13. justtrying

    Active Member

    Mar 9, 2011
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    for free, i like eagle, multisim is faster to learn if you have access to it. Hand drawn diagrams work too ;)
     
  14. GTeclips

    Thread Starter Member

    Feb 18, 2012
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    Alright, I guys Ill try and draw it in a photo editing program.
     
  15. GTeclips

    Thread Starter Member

    Feb 18, 2012
    96
    0
    [​IMG]I was having a lot of trouble making a diagram, so I just settled for a labeled pic.
    Sorry for the very sloppy wiring.

    [​IMG]

    I use the three orange wires to control the inputs. (so there basically switches)

    1 = Clock input. When connected, then both clock inputs should be high.
    2 = Controls the bottom flip-flops data input.
    3 = Controls the top flip-flops data input.

    Basically, what I'm going for in this circuit is, wire 2 and 3's value will be displayed on the top row of the display, and when you trigger the clock (wire 1), it should copy the values of wires 2 and 3 and display them on the lower section of the display. (the only reason I used a standard 7 segment display is because I don't have enough leds)

    I hope this makes it a bit more clear.
    Thank you.
     
    Last edited: Feb 19, 2012
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