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. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

    Joined:
    Nov 17, 2003
    Messages:
    39,228
    Likes:
    641
    Location:
    Derbyshire, UK
    Sorry, it would be rubbish! - a crystal is hundreds of times more accurate and stable (if not thousands?) than an RC oscillator.
     
  2. Sceadwian

    Sceadwian Banned

    Joined:
    Oct 27, 2006
    Messages:
    14,047
    Likes:
    141
    Location:
    Rochester, US
    As far as temperature stability goes, RC oscillators are horribly unstable unless you use matched NTC and PTC resistors and caps for the circuit, at which point why not just use a crystal...
     
  3. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

    Joined:
    Nov 17, 2003
    Messages:
    39,228
    Likes:
    641
    Location:
    Derbyshire, UK
    And even using the matched temperature coefficient components it's still a LONG way short of a crystals performance! - it makes no sense NOT to use a crystal.
     
  4. dave

    Dave New Member

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


     
  5. berem

    berem New Member

    Joined:
    Oct 24, 2007
    Messages:
    2
    Likes:
    0

    please help 7400 oscillator

    hello..
    I'm Turkish.my english is very bad.but I must to write the mail.
    I want to a oscillator circuit with 7400.Do you understand me.please help me.
    have a good time...
     
  6. RODALCO

    RODALCO Well-Known Member

    Joined:
    May 21, 2006
    Messages:
    1,232
    Likes:
    43
    Location:
    Akld, New Zealand
    berem, What do you want to drive with it ?

    What frequency do you require ?

    The 50 or 60 Hertz mains frequency is very accurate long term.
    Some short term variations may happen, but over a 24 hour period it is very accurate.

    A 7400 is a NAND gate, in TTL it is most often use to divide 12, 24 or 60 counters.

    Regards, Raymond
     
  7. Diver300

    Diver300 Well-Known Member

    Joined:
    Oct 19, 2007
    Messages:
    3,066
    Likes:
    101
    Location:
    England
    ONLINE
    You can use an oscillator. They are as easy to use as a 7400 IC. Just provide 5V and the output oscillates at TTL levels, or CMOS if you want.

    You can now buy oscillators that contain the dividers so you can obtain them at low frequecies like 50 or 60 Hz.
     
  8. Top Cap

    Top Cap New Member

    Joined:
    Nov 16, 2006
    Messages:
    40
    Likes:
    0
    Location:
    Watford, England
    Hi Barem, if you want to make your own basic crystal oscillator then this site may help you:-
    http://www.z80.info/uexosc.htm

    I tend to agree with the other posts on here though, you can by a ready made crystal oscillator in a can, same size as a 14 pin chip, some even have a trimmer for accurate setting.
    Les
     
  9. iyung_w

    iyung_w New Member

    Joined:
    Oct 26, 2007
    Messages:
    5
    Likes:
    0
    Last edited: Nov 3, 2007
  10. RODALCO

    RODALCO Well-Known Member

    Joined:
    May 21, 2006
    Messages:
    1,232
    Likes:
    43
    Location:
    Akld, New Zealand
    Thanks for posting that schema.

    Should't it be 23:59:59 ?

    Cheers, Raymond
     
  11. zhdsdf

    zhdsdf New Member

    Joined:
    Nov 3, 2007
    Messages:
    4
    Likes:
    0
    hi to all.....i m new member......i have to make a digital clock using TTL IC's 7492,7447,74160,7490 etc..............i have read all the threads............but i was very astonished that there was not pin diagrams of these IC's ........any one who can tell me the whole schematic diagram please tell me as soon as possible.............thaks
     
  12. blueroomelectronics

    blueroomelectronics Well-Known Member

    Joined:
    Jan 21, 2007
    Messages:
    12,536
    Likes:
    168
    Location:
    Toronto, Canada
    Just download the IC datasheets for the pin diagrams. Prefix SN to make the google search easier. SN7492, SN7447 etc...
     
  13. Krumlink

    Krumlink New Member

    Joined:
    Aug 10, 2007
    Messages:
    2,080
    Likes:
    20
    Location:
    Michigan, USA
    You should check out my binary clock (works awesome, uses up quite alot of milliamps (about 500), so it is kind of pointless to run it battery power. I should switch it over to wall plug in :D

    Mine was a ton of work, but is really cool. The attachments are the pictures of it. (wrong Computer profile, cant access my pictures :D)
     

    Attached Files:

    Last edited: Nov 3, 2007
  14. RODALCO

    RODALCO Well-Known Member

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

    Try to Google for data sheets, most of these are standard TTL IC's, otherwise try to get hold of the TTL Cookbook from Don Lancaster.

    Cheers, Raymond
     
  15. berem

    berem New Member

    Joined:
    Oct 24, 2007
    Messages:
    2
    Likes:
    0
    thanks

    hi.
    thanks for your answer.but I relinquished them.anymore it isn't my project.
     
  16. Krumlink

    Krumlink New Member

    Joined:
    Aug 10, 2007
    Messages:
    2,080
    Likes:
    20
    Location:
    Michigan, USA
    aw, you would have had fun with it like my clock :(
     
  17. RODALCO

    RODALCO Well-Known Member

    Joined:
    May 21, 2006
    Messages:
    1,232
    Likes:
    43
    Location:
    Akld, New Zealand
    Ok here are some photo's of the diagrammes to make it easier for our members who can not find these TTL IC details.

    This info is from my TTL Cookbook which i bought years and years ago, but occasionally these are for sale on Ebay.

    Info for the 7400, 7408, 7447, 7490, 7492 and 74160 attached.

    There are very good PDF files on the internet available as long the LS or SN is put in the search engine ( 74LSxx ) or ( SN 74xx )

    Hope this wil help,

    Regards, Raymond

    edited to improve picture details
     

    Attached Files:

    Last edited: Nov 4, 2007
  18. blueroomelectronics

    blueroomelectronics Well-Known Member

    Joined:
    Jan 21, 2007
    Messages:
    12,536
    Likes:
    168
    Location:
    Toronto, Canada
  19. zhdsdf

    zhdsdf New Member

    Joined:
    Nov 3, 2007
    Messages:
    4
    Likes:
    0
    thanks for reply.............
    i think now i will be able to solve my problem.......
    thanks to alll
     
  20. zajioftheasuka

    zajioftheasuka New Member

    Joined:
    Mar 4, 2007
    Messages:
    1
    Likes:
    0
    hello guys...im a newbie here...

    i need ur help, i've been making my own digital clock using this diagram...
    [​IMG]

    i already connected the minute and second digits and its working, but the problem is that it doesnt start at 00:00 rather 15:14...pls help me guys...

    and if anyone knows how to add a set and reset button...

    i appreciate ur help guys, thnx in advance...


    and BTW, ive also tried the schema posted by rodalco but i can't understand the labels on the 7490...if its R0(1),R0(2),R90,R91...:confused:

    i'd appreciate it if anyone can post a much more detailed schematic...

    thnx guys...:)
     
  21. iyung_w

    iyung_w New Member

    Joined:
    Oct 26, 2007
    Messages:
    5
    Likes:
    0
    I am not trying to discourage you, but actually its a clock, then you don't need to have the clock at 00:00 everytime you turn it on, since you already have fast and slow counter to set your clock.

    Take a look at the 7490 datasheet for pinout here:

    http://www.ee.washington.edu/stores/DataSheets/74ls/

    cmiiw, to reset the Decade Counter, MR1 and MR2 pin set to Hi. Then it will give Lo output to Q0-Q3 which will make the 7447 set the 7segment to display 0. But it looks like your 10th hour can only display '1' and blank, not '0' and '1'.

    good luck!
     

Share This Page