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Nand Gate oscillator help

Discussion in 'Electronics Homework Help' started by Harald Kapp, Sep 9, 2014.

  1. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    On behalf of IC71:


    I'm hoping I can get some help with my electronics project. I'm actually taking electronics 11 in school and we are using the "Electronic circuits for the Evil Genius"workbook.
    Unfortunately my teachers are on strike here in British Columbia Canada and I can't get any help from them.
    I'm currently on section seven, lesson 24: Building the NAND Gate Oscillator. My led light turns on when I push the button but it doesn't flash. It suppose to flash once a second for about 8 seconds, but my led stays lit.????
     
  2. Gryd3

    Gryd3

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    A schematic you are working from would be helpful ;)
     
  3. Laplace

    Laplace

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    Apr 4, 2010

    Attached Files:

    Gryd3 likes this.
  4. Gryd3

    Gryd3

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    That's a nice find Laplace.
    If that is indeed the circuit that is being constructed, it has the troubleshooting steps enclosed.
    If it is a similar, ie not exact, then I would like to know what is different and we can continue from there.

    The initial post says the LED stays lit, can it be confirmed that it stays lit for 8 seconds, or does it stay lit indefinitely?
     
    IC71 likes this.
  5. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    OK, here's the schematic:

    mono.png
    The oscillator formed by the two NAND gates in the middle is the standard two-inverter CMOS gate oscillator and should work fine, if you've built it as shown.

    All I can suggest is to check the connections to the components and pins in the oscillator circuit (pins 1~6 of the 4011). There's probably some obvious error there.
     
    IC71 likes this.
  6. Arouse1973

    Arouse1973 Adam

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    Of course it might be flashing very quickly due to incorrect values of components?
    Adam
     
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  7. Harald Kapp

    Harald Kapp Moderator Moderator

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    Right. At more than ~25Hz any flicker will be more or less invisible.
     
  8. Gryd3

    Gryd3

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    Check C2 and R4. These values will dictate the oscillation.
    I take it the 8 second timer portion works just fine?
     
    IC71 likes this.
  9. IC71

    IC71

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    Sep 8, 2014
    Thanks for the advice, I had been trying to work with the schematic, and I tried some of the trouble shooting but I still can't find the exact problem?
    If the problem is that the Hz is more than ~25Hz, how does that happen and how do I fix it?
    Here is a picture of my setup,
    I followed the schematic as best as I could, but I'm not sure if the RC2 is correctly hooked up to the IC. I've changed it around a few times but I still get the same result. The light stays lit for 8 seconds and then goes out, but it does not blink like it is suppose to.
    IMG_1971.JPG IMG_1972.JPG
     
    Last edited by a moderator: Sep 9, 2014
  10. Gryd3

    Gryd3

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    It's very difficult for me to trace some of the wires in those pictures... Most of the oscillating portion appears to be connected properly but I can't be certain.
    A more in-focus picture would be wonderful.
    Can you please post values for:
    R3-
    R4-
    C2-

    Have you tried altering the value of R4 during your troubleshooting?
     
    IC71 likes this.
  11. IC71

    IC71

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    Sep 8, 2014

    8 sec timer works, it goes off after 8sec.

    the value of the components
    R3- 470 kΩ (my DMM .458 mΩ)
    R4- 2.2 mΩ (my DMM 2.15 mΩ)
    C2- 0.1μf (my DMM 0.1μf)

    The values in the brackets are what my DMM read, but the workbook says that the resistors I'm using have an acceptable error range of 5% and its ok if they are a tiny bit off.

    I added some more pics....hope they are clear enough for you to see.

    IMG_2393.JPG IMG_2394.JPG IMG_2395.JPG IMG_2396.JPG
     
  12. Gryd3

    Gryd3

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    Can you also please confirm if you are using a 4011 and not a different series Quad NAND gate?
    I'll take a peek at the wiring.

    Take a close look at how C2 is connected to the NAND gates.
     
    IC71 likes this.
  13. Arouse1973

    Arouse1973 Adam

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    If the circuit posted is right then you have not connected it correctly. You have a resitor between pins 1 and 3, also both ends of the capacitor connect to a pin on the IC. Look at your connection again. look at R3 R4 C2
    Adam
     
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  14. Arouse1973

    Arouse1973 Adam

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    You again :) don't you watch TV? LoL
     
  15. Gryd3

    Gryd3

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    Nope. Don't have cable ;)
     
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  16. IC71

    IC71

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    I can confirm that the NAND gate series is 4011

    I am looking at the C2 and I think that I have it in correctly, but I am not 100% sure that it is.
     
  17. Gryd3

    Gryd3

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    C2 in the diagram is (I assume) the Capacitor you have bridged across your 4011 from one pin to another.
    This is the connection that needs to be looked at closer. One end of that capacitor should be connected to 3 pins of the 4011. The other end should be connected to two resistors and nothing more. The other side of those two resistors will connect back to the 4011 at their respected pin.
     
    IC71 likes this.
  18. IC71

    IC71

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    Sep 8, 2014

    If R3 and R4 don't connect between Pins 1 and 3, then how do they connect? In the schematic, it looked like the resistors are between pins 1 and 3 . I uploaded the the schematic I'm working from.
    IMG_1038.JPG
    If the capacitor doesn't directly connect to the IC, then do I use just use extra wires?

    I' m not 100% sure where and how the R3 R4 C2 connect. Is there any way you can tell me how they do?
     
  19. Gryd3

    Gryd3

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    Well... R3, R4, and C2 will all connect together with an unused line on your protoboard.
    Then the free ends will connect to your 4011.

    I should clarify in that both sides of the C2 Capacitor are not supposed to be directly connected to the 4011, only one side is. The other side will connect through the resistors R4 and R3 to different pins.

    Take a look at your drawing and note which pins C2 is connected to. One side is connected to pins 4,8,9. The other side is not connected to the 4011, but is instead connected to resistors.

    This may be hard for me to explain. I'll try to give a quick drawing in an hour or two.
     
    IC71 likes this.
  20. IC71

    IC71

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    Thanks soooo much!!! it works now!! I've been stuck on this for almost 2 weeks. I can't believe I couldn't find out what the problem was.....it was easy once you explained it...it makes so much more sense now :)
    Your awesome! Thanks to everyone for helping me with this, I really appreciate it, now I can move on through the rest of the course. I'm really glad there is a place like this to go to.
     
    (*steve*) and Arouse1973 like this.
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