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Please help me with this 4017decade counter and 555 timer. I am a beginner

Discussion in 'General Electronics Discussion' started by Vignesh0025, Jul 11, 2013.

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  1. Vignesh0025

    Vignesh0025

    9
    0
    Jul 4, 2013
    Hello,

    I am a newbie in electronics. Some days ago, i managed to make a running led display using 4017b decade counter and 555 timer(and made another on with 4026 decade counter with a seven segment display and same 555 timer ) and also uploaded to youtube to show it to my friends. It was working perfect that day :eek: and i disassembled everything from the bread board after that.

    Here is the circuit!!
    http://www.technologystudent.com/elec1/count1.htm

    Here goes the output i got a week ago


    Here is the out put i got yesterday


    Yesterday, I made the same circuit but now it is not working.!!!! . I checked twice the circuit, I changed the ic4017 three to four times, I changed the 555 timer, even i bought a new bread board and tries with it also. But it's not at all working. I checked everything. But I am not able to identify the problem at all.


    Not only that, instead of 4017b, i tried with 4026 decade counter and the seven segment display is scrambling and like anything and showing some random things. Please help me!!! I am really tired and fed up with this electronics. The only thing is that 555 timer produces pulse as expected. I tried a LED with its output. Its blinking as expected.
    But none of the other things are working!!!! :( :( :( :( :( :( :(
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    First thing to do is to wire up a LED with a 1k resistor to the output of the 555. That way you can check that it is oscillating correctly and see what happens on each transition.

    Have the speed nice and slow so you can see what's going on.

    I suspect a wiring error or noise from the 555 interfering with the 4017.

    Check the power and ground leads are connected and that there is no input on the 4017 that is floating.
     
  3. Vignesh0025

    Vignesh0025

    9
    0
    Jul 4, 2013
    Thank you very much for your reply brother... I added that 1k to 555 output... still its not working... :( is there is any way to find whether noise is there from 555??? If so how to fix it... please reply ...
     
    Last edited: Jul 11, 2013
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    Is the led you connected to the 1k resistor flashing?

    Do all of what I suggest on line 1.

    Then line 2

    Then line 4. Especially line 4.

    Then tell me what it's doing.

    Don't worry about interferance too much until you've checked the wiring. Maybe remove it all and start again.

    The 1k resistor and the LED will tell you if the 555 part is OK. The LED should go On Off On Off On Off...
     
  5. Vignesh0025

    Vignesh0025

    9
    0
    Jul 4, 2013
    led connected to 555 output thro 1k is perfectly blinking brother... but 4017b, the same problem still exists.. how to check the ground and power? any specific idea?? :( but Contacts are ok...
     
  6. Vignesh0025

    Vignesh0025

    9
    0
    Jul 4, 2013
    And another thing i found just now... I am using a 12 V ac to dc adapter.. its giving around 11v to 12v DC (its just keep on varying) and also 25V AC ... it it normal ... will ac voltage be there with dc also??
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    Can you try running this from a battery and seeing it that makes any difference.

    Also, take a picture of the breadboard that is sharp enough that I can clearly read anything written on the components and I'll try to identify what you may have done.
     
  8. Vignesh0025

    Vignesh0025

    9
    0
    Jul 4, 2013
  9. sndscientist

    sndscientist

    47
    1
    Jul 10, 2013
    i personally have been using the 4017 and 555 for many many years now. if your showing 25vac on a 12 volt transformer that can be a huge problem.

    the chips are c-mos meaning they have a working voltage of 3-18 Vdc. i'm assuming the supply your using is a normal linear wall wart. (transformer not sps) to have ac showing your filter capacitor inside of the power supply has probably gone bad.

    try putting a 25 volt >2200Uf capacitor across the voltage source going into the bread board. or as was previously suggested try it on a 9 volt battery.

    Also i didn't see you using resistors in series with the led's. the 4017 has a rated output of just around 5ma. it wasn't designed to run led's directly, but rather it was designed be a logic level counter. you might have cooked them. are the LED's your using the ones with built in resistors? i noticed from your video they look awful bright for being driven directly from a 4017.




    another problem i have seen with this circuit is the 555 sometimes becomes corrupted. for that try inserting a bias resistor between pin 3 (output of the 555) and ground. i'd use a 2.2K simply because your just trying to sink it back to ground not dissipate any power





    ******
    you forgot the current limiting resistor on the common. you probably burnt out the 4017's
     
    Last edited: Jul 11, 2013
  10. Vignesh0025

    Vignesh0025

    9
    0
    Jul 4, 2013
    I am a very beginner.... What should be the value of current limiting resister for 4017 ? And I tried with a 9V battery also... Still same problem :(... If ic's are burned out, how to check that??.... I have 4 of them.... I tried with all the four... They give exactly same output... Also i added the bias resister, 63v 2500uF capacitor everything you said... Still Not working.... Thank you for the reply
     
  11. Vignesh0025

    Vignesh0025

    9
    0
    Jul 4, 2013
    I am completely fed up with this electronics :( :(
     
  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    It looks to me like the blue wire link joining up the Vcc connection on the 555 board may be disconnected.

    This will cause the 4017 to be powered by the 555 output through the protection diodes and I'd not be surprised at a display like you're getting.

    I also note that you're not using a current limiting resistor for the LEDs. This is shown in your schematic and is there for a reason.

    Now, some tips:

    1) use red wires for Vcc
    2) use black wires for ground
    3) use other colours for other signals
    4) wire up Vcc to the "top" of your breadboard
    5) wire gnd to the "bottom" of your breadboard

    This makes looking at the circuit more intuitive and matches a little more closely what you'd draw on a schematic.

    I note that your circuit generally has the inputs on the left and the outputs on the right with signals going left to right. This isn't essential either, but it can also make it easier to follow what's going on. (contrary to advice above, this has probably done no harm to the 4017's but it's not to be recommended)
     
  13. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    CMOS as noted above has outputs designed to drive logic, not power. As such, they tend to have a fairly high output impedance and this effectively limits the output current. Note that this IS NOT true of all logic chips!

    You'll find the specs give very low limits on current source/sink, but these are the limits if you require the outputs to maintain a valid logic level -- in this case you do not.
     
  14. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    Look at the 1.2k resistor (it's not critical, 1k would be fine too) in the schematic connected between all the cathodes of the LEDs and ground.

    If you followed the schematic you showed us, you missed this.
     
  15. sndscientist

    sndscientist

    47
    1
    Jul 10, 2013
    i'm sorry i did not explain myself right. The 4017 needs a nice stable voltage inside of it's range (3-18) they are temperamental with fluctuations. assuming from your first post your using a 12Vdc adapter.

    the fact that you see 25vac and that you said the dc isn't stable concerns me. it sounds like you may have fried a diode or filter cap in your supply. not necessarily something you did wrong. the wall warts can be finicky. what type of battery were you using?

    i took about 20 mins and i studied your pictures and looked at the diagram of what you were building and i noticed R3 was missing. [​IMG]


    the purpose of R3 is current limiting for the LED's as well as the 4017. i thought i saw it in the working video but it's missing from the images.

    so to recap;
    i would get another transformer, 25 vac on a 12vdc transformer is very bad try a 9vdc one if you can find one. it should read about 10.2 with no load

    The project you shared is based on a 9 volt source, did you change the resistor values to reflect 12 volts
    ****edit*****

    my machine isn't updating web pages properly
     
    Last edited: Jul 11, 2013
  16. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    Since he gets the same problem when he runs from a battery, it's almost certain that there's *not* 25VAC on his DC supply.

    I pointed out a wiring error which is more likely to be the problem (especially since it was working and then it wasn't).
     
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