help with 555 timer

Discussion in 'The Projects Forum' started by starrz, Jan 6, 2013.

  1. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,936
    1,428
    Do you have the power on reset circuit (D4, C6, and R9) built? If not, put that in and see if that solves the problem. And don't forget the pull down resistor, R2.
     
  2. ScottWang

    Moderator

    Aug 23, 2012
    6,742
    1,045
    Q1 need to add a Rbe to off the Q1, otherwise when there is no any input signal, then B_Q1 will become a floating status.
    Maybe starrz can modify to suit his needed, or describe more details.

    In your list, if the relay need to work from the power up, then the Q0 of CD4017 shouild be add a 1N4148 and connecting to R1.
     
  3. ScottWang

    Moderator

    Aug 23, 2012
    6,742
    1,045
    You may connecting rst of CD4017 to GND to try it first.
    Add a Resistor and LED at pin 3 of NE555, to check if it's working probably.
    About the rst of CD4017, the value of R and C can be reduce more like 100K and 0.1uf etc...
     
  4. starrz

    Thread Starter New Member

    Jan 6, 2013
    17
    0
    this is exactly what is desired from this circuit , i definitely dont have those extra components but i will add them in and see what it does.
     
  5. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,936
    1,428
    I have the entire circuit except the relay breadboarded and working. It's possible that the schematic that I posted doesn't exactly represent what I built because I am watching the ballgame with one eye and the computer with the other. However, I am satisfied that the solution is very close.
     
  6. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,936
    1,428
    What value Rbe for Q1 do you think? 10k?

    I think I have a diode on the output 0 of the 4017. Look again.

    Thanks for your input.
     
  7. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,936
    1,428
    I think the power-on circuit is needed to ensure that the 4017 always starts with output 0.
     
  8. ScottWang

    Moderator

    Aug 23, 2012
    6,742
    1,045
    4.7K~10K is ok, because this is similar as static DC, so it just make sure the B_Q1 is no floating, when there is no any signals input.

    I knew that, it just easy to try.
     
  9. starrz

    Thread Starter New Member

    Jan 6, 2013
    17
    0
    thanks guys for the help so far, tracecom yours is wired and working , you got the latching effect when output 2 reaches high?
     
  10. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,936
    1,428
    Yes, when output 2 goes high, it stops the 4017 via the clock enable pin. When I disconnect the power and reconnect it, output 0 goes high for 2 seconds, then output 1 (which is connected to nothing) goes high for 2 seconds, then output 2 goes high and stays high until I disconnect the power and reconnect it.

    Attached is the (hopefully) finalized circuit drawing. Note that many of the component reference numbers have been changed in order to make them sequential. Also note that I used 1N4148 diodes instead of 1N914 as shown, but either should work.
     
    Last edited: Jan 8, 2013
  11. tinamishra

    New Member

    Dec 1, 2012
    39
    1
    Nice conversation is held here and know good information about 555 timer i would like to share some little information which i have read on a site that is The 555 timer IC is an integrated circuit used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element. Derivatives provide up to four timing circuits in one package.
     
  12. ScottWang

    Moderator

    Aug 23, 2012
    6,742
    1,045
    I would like to hear about that, do you have any practical application circuit?
     
  13. starrz

    Thread Starter New Member

    Jan 6, 2013
    17
    0
    hey guys i got as far as the leds counting in 2 second intervals as desired just about to connect the 3904 and relay when i decided to bump up the 9v battery to a 12v source via ac adapter instead , all leds just came on flashing randomly like maybe 10x as fast as before in no particular order. I then decided to go back to the 9v battery as power source and now it makes a full cycle of ten counts 3x and then all stays very dimly lit. when i shut power off and back on it again it still repeat this pattern. Did the ac adapter overwhelm something in the circuit and possibly damaged it?
     
  14. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,936
    1,428
    It isn't likely that a simple change from 9V to 12V would hurt anything or make any change in the operation of the circuit. I am using a 12V wall wart with no issues. Did you connect the power with reversed polarity...even briefly? If not, maybe you disturbed some connection on the assembly.

    ETA: Your wall wart should be regulated 12VDC. If it isn't regulated, the voltage under no or light load could exceed the maximum of the IC's, and they may be damaged.

    Another thought: Try powering the circuit with a fresh 9V battery. If it works properly, there is no component damage, which means that the wall wart you have is noisy and will need to be filtered and/or regulated.
     
    Last edited: Jan 8, 2013
  15. starrz

    Thread Starter New Member

    Jan 6, 2013
    17
    0
    yeah actually i did connect the power in reverse by mistake, darn i guess i killed something. tracecom the 4017 still functions as it should when you make manual + pulses to the clock input (pin14) so i guess the problem surrounds the 555 timer and its output.
     
  16. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,936
    1,428
    Probably so. Just replace the 555 and try it again with a good battery. But before you try the wall wart again, check the no load voltage on it. If it's over 18V, definitely don't use it, and personally, I wouldn't use it without regulating it to 12V.
     
  17. starrz

    Thread Starter New Member

    Jan 6, 2013
    17
    0
    15v no load on my wall wart, the 555 jus wont pulse anymore, i have swapped 555s but still in circuit as is. Am gonna try and build it from scratch again and check back on connections, so close:(
     
  18. starrz

    Thread Starter New Member

    Jan 6, 2013
    17
    0
    strange thing though when i remove c1 it goes back to normal
     
  19. starrz

    Thread Starter New Member

    Jan 6, 2013
    17
    0
    update, it does 3 full cycle well and starts to flash randomly then I place in back again then it goes back to normal, it does the 3 full cycle thing again after which i remove it. I dont know why but the removing and placing back seems to have some sort of resetting effect on the 555
     
  20. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,936
    1,428
    Try a new C1. Maybe the reversed voltage damaged it. It is also possible that your battery is low; have you tried a new one?
     
    Last edited: Jan 8, 2013
Loading...