HELP PLEASE -Simple but I have it WRONG

Discussion in 'The Projects Forum' started by usdiggs, Jan 16, 2007.

  1. usdiggs

    Thread Starter New Member

    Dec 4, 2006
    8
    0
    Hi,

    I am trying to build a simple counter. I have had it all drawn on CAD software and tested and it worked fine but when I go to put it on the breadboard nothing happens.

    When I test the voltage between the high and low rails I am only gettign 0.9V from the 9v battery.

    At the moment nothing at all is happening, and I have tried resetting it etc.

    Any help would be much appreciated.

    Thanks
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Problem number one is that you appear to be using TTL devices powered by 9 volts. That is a no-no. The maximum TTL power supply is 5.25V in most cases.

    Second, I can't see clearly that the 7-segment driver has its power pin tied to the +power bus.

    Before you proceed you need to find a +5 volt power source.

    hgmjr
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    Yep, it's less messy than when the production line put the 320 volt wiring into the 5 volt bus, but the chips are just as dead. One way out of this is to use a 7805 regulator to drop your battery voltage, or to substitute 4000 series CMOS chips so you can use the full nine volts.
     
  4. usdiggs

    Thread Starter New Member

    Dec 4, 2006
    8
    0
    I have added the regulator and replaced the chips, but am still getting no joy. THe common from the display is going to +ve.

    I am very new to this so quite possible I have made a stupid mistake :)

    Thanks for your help.
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    What is the clock source for the '193? I don't see anything on the breadboard but the counter and display driver.
     
  6. BobaMosfet

    Active Member

    Jul 1, 2009
    109
    11
    Yeah, there are a lot of other things needed here. A voltage regulator, capacitors, a crystal... You also need to make sure you hooked the 7Seg Display up right and didn't burn it up.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    That 0.9v reading is a big clue as to what is wrong.

    You very likely have an OUTPUT of one of the TTL ICs connected to the +V rail or ground.
    Check to make sure that your pins 12 and 13 on the 74193 are disconnected.
    Check to make sure that pin 4 on the 74247 is disconnected.
     
  8. jj_alukkas

    Well-Known Member

    Jan 8, 2009
    751
    5
    How come your battery reads 0.9V?? Have you shorted something or is your battery dead? Track it first.

    Posting a schematic would help a lot than a breadboard photo.
     
  9. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Good comments, all.

    This is an ancient thread from 2-years ago. I am afraid this member has moved on to other forums since he has not logged onto AAC since October 2007. I suspect we will never hear from him again.

    hgmjr
     
Loading...