help!! 24 secs counter using JK(7476) 555timer 7segments and ic7447

Discussion in 'The Projects Forum' started by ouchs, Sep 12, 2013.

  1. ouchs

    Thread Starter New Member

    Sep 12, 2013
  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    No circuit shown...
  3. tshuck

    Well-Known Member

    Oct 18, 2012
    Over 2MB for a .BMP!?

    Upload it here and you'll find you get more help...
  4. ouchs

    Thread Starter New Member

    Sep 12, 2013
    sorry im newbie here ... did the jk7476 is one count down and the other is count up?
  5. GopherT

    AAC Fanatic!

    Nov 23, 2012
    Is it critical that these chip are selected? Otherwise, you could feed your 555 into a BCD counter, to create a 4-bit 0-10 value. Then feed that binary value into a seven-segment decoder. That give you the first digit.

    To get the tens digit, get a second pair of BCD counter/7-segment decoder. For this one, the 555 timer does not drive it, instead there is a divide-by-ten output on the first BCD counter that drives the 10's digit BCD counter.

    You can cascade as many as you want.

    To reset (or stop) at 24, you can use a hex inverter chip and an 8-input AND gate. the goal here is to create a signal that can control the 'disable' pin on the first BCD counter (prevent it from counting even though the 555 continues to pulse.

    Look for CD4510 and CD4511 chips if you want to go old-school. I don't remember the 74-series equiv.
    Tie the reference inputs to binary 24 (high or low as needed), and then