1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

TTL Clock with 7447 7490 and 7400 IC's

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by RODALCO, Nov 28, 2006.

  1. krye

    krye New Member

    Joined:
    Aug 19, 2008
    Messages:
    5
    Likes:
    0
    You're right. It's wrong. It's all wrong! I don't know what I was thinking. I removed the schematic so I can redo it.
     
    Last edited: Aug 26, 2008
  2. mneary

    mneary New Member

    Joined:
    Feb 27, 2007
    Messages:
    4,502
    Likes:
    67
    Location:
    California USA
    @krye: The flip flop should be set to toggle on the falling edge of the "1" driver.
     
  3. on1aag

    on1aag New Member

    Joined:
    Jul 31, 2006
    Messages:
    512
    Likes:
    8
    Maybe like this ?

    on1aag.
     

    Attached Files:

  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. mneary

    mneary New Member

    Joined:
    Feb 27, 2007
    Messages:
    4,502
    Likes:
    67
    Location:
    California USA

    That's the basic idea.
     
  6. krye

    krye New Member

    Joined:
    Aug 19, 2008
    Messages:
    5
    Likes:
    0
    Cool, thanks

    K
     
  7. FLores

    FLores New Member

    Joined:
    Sep 10, 2008
    Messages:
    2
    Likes:
    0
    Location:
    Philippines
    RODALCO PLS EMAIL ME THE SCHEMATIC DIARGRAM OF DIGITAL CLOCK WITH 555 TIMER pls. ..

    sweet_ko2007@yahoo.com
     
  8. FLores

    FLores New Member

    Joined:
    Sep 10, 2008
    Messages:
    2
    Likes:
    0
    Location:
    Philippines
    I need the diagram of digital clock with 555 timer

    Help me guys!!
     
  9. pao_wikhan

    pao_wikhan New Member

    Joined:
    Sep 8, 2008
    Messages:
    5
    Likes:
    0
    im having problem with my clock hour simulation...my 12:00 time isnt goin back or rather resetting to 00:00...how am i goin to do so..im using ttl gates mainly 7490 & 7492 as seconds mins and hours...nid help..tnx
     
  10. sali147

    sali147 New Member

    Joined:
    Nov 11, 2009
    Messages:
    2
    Likes:
    0
    i have made a keypad 3*4 scanner and now i wanna to make a simple adder and mutiplier with keypad 4*4,anybody helps me?
     
  11. cacophony

    cacophony New Member

    Joined:
    Mar 11, 2010
    Messages:
    9
    Likes:
    0
    Hi! Could you send me a copy of this schematic in a large-scale so I could clearly see the pins? I've built a schematic just this morning and ericgibbs told me that it might take a while to debug the errors. Could you also please point to me where the errors are? BTW, I've based my schematic on the attached file seen in one of the topics here about digital clock originally made by Sujoy Mukherjee et al.

    Thanks!
     

    Attached Files:

  12. RODALCO

    RODALCO Well-Known Member

    Joined:
    May 21, 2006
    Messages:
    1,232
    Likes:
    43
    Location:
    Akld, New Zealand
    TTL clock

    cacophony

    Attached schema is the only schema I have drawn up and works fine.

    As long as the 100 nF decoupling capacitors are attached across the voltage terminals of the IC's it should work with no major problems.

    My clock is now nearly 22 years old and happily ticking away in TTL technology.
     
  13. Lazze

    Lazze New Member

    Joined:
    Jun 7, 2010
    Messages:
    3
    Likes:
    0
    Hi guys !

    I'm doing my first TTL clock and I'd be clad if someone could check my schematics briefly for any errors.

    Thanks.
     

    Attached Files:

  14. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,449
    Likes:
    937
    Location:
    Canada, of course!
    ONLINE
    Your 4521 is ordinary Cmos, not old TTL. So its max oscillator frequency is only 0.9MHz, not 4.2MHz when its supply is only 5V.
    The output current of the 4521 oscillator is too low to drive the old fashioned TTL counters. Maybe a 74HC4521 will work.

    When the switch is turned on then you have outputs shorted together. Which output will win?
     
  15. Lazze

    Lazze New Member

    Joined:
    Jun 7, 2010
    Messages:
    3
    Likes:
    0
    Audioguru, thank you for your tips. I'm a complete novice what comes to electronics but I'm eager to learn ;)

    Are you sure the 4521 can't handle that >4MHz frequency? I thought the limit was more around 6 MHz. You also said there wasn't enough current to so I put an Mosfet driving that first counter and couple of diodes to those minute and hour adjustment circuits. (btw, I made those switches debounced.) and now there are also switches for seconds reset and counter stop.

    Any comments?
     

    Attached Files:

  16. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,449
    Likes:
    937
    Location:
    Canada, of course!
    ONLINE
    Your Mosfet symbol is for a Jfet and does not show its drain or source pins. If its source is connected to ground then its drain is its inverted output but its drain is not connected to the counter IC. Instead, the counter's clock pin is wrongly connected to ground.
     
  17. Lazze

    Lazze New Member

    Joined:
    Jun 7, 2010
    Messages:
    3
    Likes:
    0
    Again thanks for clarifying things up.

    I corrected the mosfet symbol, changed the output location and increased the gate-to-ground resistor to 100k.

    How does this look like?
     

    Attached Files:

  18. mneary

    mneary New Member

    Joined:
    Feb 27, 2007
    Messages:
    4,502
    Likes:
    67
    Location:
    California USA
    Your schematic shows a "4521N" which is the generic number, and the original ones were very slow on 5V. If you have a CD4521B, you would be lucky to get one MHz. If it's an HCF4521 from ST it might be good to 2MHz. Only newest ones (HEF4521) from NXP are guaranteed at the speeds you expect.
     
  19. global_wonda

    global_wonda New Member

    Joined:
    Sep 24, 2010
    Messages:
    3
    Likes:
    0
    Location:
    Abuja
    Hello everyone, am new here. I'v alwayz found this forum very interesting and educative. Pls, i want you guys to help me on HOW TO CONFIGURE A 74LS161 modulo 16 COUNTER TO WORK EXACTLY AS A 74LS160 MODULO 10 COUNTER.
     
  20. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,449
    Likes:
    937
    Location:
    Canada, of course!
    ONLINE
    I was wondering why you use antique old TTL logic. Then I looked in Google to see that you are in Nigeria. Too bad.
     
  21. RODALCO

    RODALCO Well-Known Member

    Joined:
    May 21, 2006
    Messages:
    1,232
    Likes:
    43
    Location:
    Akld, New Zealand
    7447 IC pin details

    Hi, I'm not going to redraw the schematic as I haven't got the time for that.
    I give you the pin details for the 7447 IC

    PINS
    1 BD
    2 R0,1
    3 R0,2
    4 NC
    5 Ub+
    6 R9,1
    7 R9,2
    8 Qc
    9 Qb
    10 U- (neg)
    11 Qd
    12 Qa
    13 NC
    14 A
     

Share This Page