Are my cd4510 counters connected correctly?

Discussion in 'Digital Circuit Design' started by Arjune, Jan 6, 2018.

  1. Arjune

    Thread Starter Member

    Jan 6, 2018
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    Is my 59 to 00 counters for a clock connected without anomalies. I am concerned about timing and rising or falling logic levels causing the count not to be 60 changes per minute or seconds. I attached a pdf scanned file of the schematic I made on paper. I use an OR gate, 2*cd4510, AND gates and Inverters and a power supply of about 7 volts from an AC adapter with switchable voltages (3V-12V). I don't have an oscilloscope and don't think I know how to use one for checking the clock compared to outputs states. Upon observation, with 4 leds connected to outputs of both cd4510 with 1Kohm resistors, it looks fine but I doubt my abilities. Can those outputs only handle 3mA.
     
  2. dl324

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    Not even. Since you're also using the outputs to drive other gates, a safe current is more like 0.5mA.
     
  3. MrChips

    Moderator

    Oct 2, 2009
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    I stated in another post recently, don't use an output as a logic source if you are already driving LEDs. Drive the LEDs using a buffer. In your case, use CMOS inverters.
    LED Output.png
     
  4. AnalogKid

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    Aug 1, 2013
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    Looks pretty good. * * * * for going all discrete.

    I see that when counting down, you detect a roll-under from 00 to 99 by testing the upper digit 8 output, which always is invalid, and using it to load a 59 into the counters. Can't you use a similar shortcut when counting up? In your schematic you decode a 60 and use that to force a reset to 00. But don't you only need to decode the upper digit 6? Anytime the upper digit is 6 when up-counting, all lower digit values are equally invalid. This eliminates 4 AND gates and 4 inverters.

    If you want to stay with decoding the full 60, you can eliminate a lot of gates if you detect the lower digit 0 with four diodes, a 10 K resistor, and an inverter. This eliminates three inverters and three AND gates.

    The 4510 is not intended for direct drive of a display, but it should make enough current for your LEDs to at least be visible enough to confirm that your circuit is working. If you need more output current, a ULN2803/04 has 8 excellent LED drivers in one package.

    Where are you located? Is this for school, work, or fun?

    ak
     
    Last edited: Jan 6, 2018
  5. Arjune

    Thread Starter Member

    Jan 6, 2018
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  6. dl324

    AAC Fanatic!

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    I thought that might have been you sporting a new member name.
     
  7. Arjune

    Thread Starter Member

    Jan 6, 2018
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    The output voltage at Q of the cd4510 only drops a little with the LEDs (less than 1 volt). TTL ICs use more current and the operating voltage is limited. If I do pursue the clock, I plan to use the cd4511 and drive 7 segment displays. I just didn't have room on the breadboard to assemble them. My vision is not that good; I will have a problem to assemble the circuit on a pre-drilled board with contacts close together during soldering. I don't have the skill like I used to to make a printed circuit board using an etch-resist pen. I am sure I see reality with my mind and not my eyes. My eyes appear dead.
     
  8. Arjune

    Thread Starter Member

    Jan 6, 2018
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    I am suspicious of your confidence. It seems there may be an attempt to change the polarity of thought to change my gender using the circuit scenario. Since I am a schizophrenic, I feel the need to be honest although I am applying paranoia.
     
    G.ravi likes this.
  9. Arjune

    Thread Starter Member

    Jan 6, 2018
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    Analog Kid; are you talking about an 4 input AND gate using diodes with an inverter to detect the lower 0. You are saying that will eliminate the 4 inverters and 3 AND gates? I don't think the logic will work. 20180107_143135.jpg
     
  10. absf

    Senior Member

    Dec 29, 2010
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    I think what AK meant was this...:D

    4002.PNG
     
  11. AnalogKid

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    With an inverter connected to the output Z, this circuit becomes a NOR gate, which is the equivalent of an inverted input AND gate (DeMorgan's Theorem).
    [​IMG]
    ak
     
  12. Ronald Arjune

    New Member

    Apr 28, 2016
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    I think I believe it now AK. I could use 4 diodes and an inverter and that would replace the 4 inverters and the three AND Gates. I see the logic now. Thank you-I will try it. Can you please tell me how you made the schematic because I don't want to be using paper and pencil.
     
  13. AnalogKid

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    To replicate your circuit remember that there must be an inverter after the diodes.

    I didn't draw that schematic; I found it on the web searching for 'diode-or circuit'.

    http://www.circuitstoday.com/logic-gates

    ak
     
  14. Arjune

    Thread Starter Member

    Jan 6, 2018
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    Analog Kid I wired the inverted OR gate with the 4 diodes, a 10k resistor to ground and a 4049 inverter and the circuit worked. This saved me gates and would simplify wiring. Thank you very much for your insight.
     
  15. AnalogKid

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    Glad it worked for you.

    ak
     
  16. Arjune

    Thread Starter Member

    Jan 6, 2018
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    This attached file is my mod 12 counter clock interfaced .png clock interfaced .png clock interfaced .png I intend to use with the mod 60 I designed. Would it just be a straightaway connection of both to create a forward and reverse clock?
     
  17. Arjune

    Thread Starter Member

    Jan 6, 2018
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    My mod 12 counter is working and I plan to connect it to the mod 60 counter to make a clock. I will use 4 diodes and a resistor to ground with an inverter at the output to replace the 4 inverters and 3 AND gates as Analog Kid suggested. Will I be able to just connect the OR gate pictured between both the mod 60 and 12 for the circuit to work (up and down)? clock interfaced .png
     
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