Rev counter

Discussion in 'Homework Help' started by Energetic, Mar 11, 2011.

  1. Energetic

    Thread Starter Member

    Jan 3, 2011
    33
    0
    This is an attempt at a rev counter. It must count to the nominated rps (0-99) then latch, reset and restart the count.

    I have used a generator to simulate the motor. The switches must go and it must operate automatically.

    i have been advised to use monostables to generate a reset pulse after the displays latch.

    As you can see, none of what i have done works. the counter does not even count properly and i am out of ideas.

    A shunt in the right direction would be very helpful.

    Cheers...
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    There are some problems with your logic. I can't see how the data gets latched into the 'LS75s. The latches can't drive 7 segment displays directly, unless you only want to indicate the count of 99. Even at that, 6 of the 7 drive lines are needed, and the latches can't handle the current - I can't see if the displays are common anode of common cathode. You would be better to use decoder/drivers like 'LS47's.

    Is this supposed to show the count increasing from 00 to 99? If that is the case, you will need more external logic to latch the count out of the 'LS160s after each clock. You may find that both counters count simultaneously - I can't make out the labels well enough.

    Do you have data sheets for all your logic? That will give a lot of help. Just use the device number as a search term.
     
  3. Energetic

    Thread Starter Member

    Jan 3, 2011
    33
    0
    It must show the count from 0 to whatever the generator is set to, latch, reset and restart the count.

    i am thinking after your advice, this order:

    74LS160N then into the 7475 latches then into the 7447s to the CA 7 seg displays.

    In the previous design i have had a counter and 2 latches for each diplay, is this the right idea do you think?
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    The counter out is 4 bits. The latches can hold 4 bits each. What would you do with the other latch?
     
  5. Energetic

    Thread Starter Member

    Jan 3, 2011
    33
    0
    Fair enough, good point... How then do the outputs from the '75 connect to the 7447?
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Do you have the data sheets? Outputs go to inputs.
     
  7. Energetic

    Thread Starter Member

    Jan 3, 2011
    33
    0
    yes, i'm just not sure about the inverting outputs...

    Also the ones on the data sheet have more outputs than the one i've got in multisim???
     
    Last edited: Mar 14, 2011
  8. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    If that is the '47 outputs, that merely means the IC is meant to drive a common anode display.

    What have you got for a schematic?
     
  9. Energetic

    Thread Starter Member

    Jan 3, 2011
    33
    0
    I have done something else with '47's and a 7seg CA display recently so will paste that in.

    In the other post i was referring to the outputs on the '75's. The data sheet i have shows the 75 with 4 inverting outputs and 4 non-inverting outputs. The one i found in multisim has only 2 of each so i was unsure about how to connect it to the '47s. 4 outputs to 4 inputs seems a more sensible idea.

    Also what's the best IC to build a 0-99 counting circuit with? I have used the '160's but am open to suggestions...

    Don't have a schematic really, only the pic of the first attempt which i posted...
     
  10. Energetic

    Thread Starter Member

    Jan 3, 2011
    33
    0
    It probably doesn't look like much has changed but i've spent an awful lot of time not changing much! If you had trouble making out the last one you'll love this...

    Needless to say it still doesn't work...

    still confused about the outputs from the latches as mentioned in the previous post...

    please help...:confused:
     
  11. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Actually, if the counters are running correctly, just attach the outputs to the 'LS47's. Since you are following the count, a layer of latches is unnecessary.

    Unless this is still in effect -
    If you have to use the latches, the time to latch the count is right after it has advanced. If the counter goes on the leading edge of the clock, the latch can go on the trailing edge.
     
    Energetic likes this.
  12. Energetic

    Thread Starter Member

    Jan 3, 2011
    33
    0
    I do need the latches sadly but my counters are not working correctly still. Is there any guidence on how to set them up for a 99 count? I still don't have anything on the outputs of the '160's...
     
  13. MrCarlos

    Active Member

    Jan 2, 2010
    400
    134
    Hello energetic

    This could help keep up with your project.

    Greetings
    at your service
     
    Energetic likes this.
  14. Energetic

    Thread Starter Member

    Jan 3, 2011
    33
    0
    Cheers MrCarlos. Where did you find this? I have built it but alas i cannot even get it to work with something to copy... Perhaps i have done something wrong or my 555 is connected in wrong??? I have used a hex display, is this correct?

    Getting a bit fed up with electronics now, might go back to making pizzas...
     
  15. MrCarlos

    Active Member

    Jan 2, 2010
    400
    134
    Hello Energetic

    First Off All I’m Sorry for my Delay. I have not receive any notification of your answer.
    The Use Of HEX Display’s is correct.

    Now: I Think Your 555 Is not running Properly, Verify It Please. Check connections and components.

    Greetings</SPAN>
    at your service
    </SPAN>
     
  16. Energetic

    Thread Starter Member

    Jan 3, 2011
    33
    0
    Hi,

    Thanks for your reply I have changed a few things around and have come up with something that works. i have used 74123 monostables to reset the 74160 counters and the 7475 latches to latch the displays. I have spent so much time on it now i am moving on...

    Thanks again...
     
Loading...