Troubleshooting a 1Hz time base

Discussion in 'The Projects Forum' started by kurtruk, Jan 20, 2013.

  1. kurtruk

    Thread Starter Member

    Aug 26, 2012
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    So I have assembled the schematic on a perfboard, but when I turn it on the LEd is solid instead of blinking. It is my first time soldering, but I've closely examined all my joints and they look ok. The resistor and capacitor values are a bit crazy because I didn't have the exact value. What I am thinking is that basically the LED soldity just means the 4013 is working. So how would I attempt to trouble shoot this?

    Here is the 4060 data sheet: http://html.alldatasheet.com/html-pdf/11960/ONSEMI/MC14060BCP/940/5/MC14060BCP.html
     
  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The 18 M is rather high, a 10 M might also work.
    What is the value of Q1 , the cristal

    Bertus
     
  3. kurtruk

    Thread Starter Member

    Aug 26, 2012
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    The datasheet says to use 18M, so I don't know But I could try. The crystal is a 32.768kHz 12.5pF
     
  4. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    I don't see any LED in the schematic.

    Are you sure that the oscillator frequency should be 1Hz? It looks to me like it would be several kHz, in which case an LED would be flashing much too fast to see, and would appear to be on continuously.
     
  5. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The following circuit is given in the fairchild datasheet of the 4060:

    [​IMG]

    Bertus
     
  6. kurtruk

    Thread Starter Member

    Aug 26, 2012
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    The LED is connected to the output (pin1) of the 4013. As far as frequency isn't a 32768/2^15=1 because the 4060 has 14 counting stages and the 4013 is another so 15 stages should equal 1hz, right? How did you come up with several kHz?
     
  7. kurtruk

    Thread Starter Member

    Aug 26, 2012
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  8. tubeguy

    Well-Known Member

    Nov 3, 2012
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    The capacitors aren't adding up. :)
    Capacitors in series/parallel work opposite of resistors.
    You could try using just a 33pf instead of a 39 and three 33's in series to make 11 (10) pf. And sometimes caps in series are iffy.
     
    Last edited: Jan 20, 2013
  9. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    And all those resistors and capacitors wired on a perfboard probably have all sorts of nasty capacitance from the layout. I would bet it's not oscillating.
     
  10. kurtruk

    Thread Starter Member

    Aug 26, 2012
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    I connected a LEd in between one of the outputs of the 4060 and the LED appeared solid, so that cause me to think it is oscillating at a overtone. I uses the Motorola data sheet because my ic is Motorola and that is where I got my cap values. Any advice of what to try.
     
  11. tracecom

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    Apr 16, 2010
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    Do you have pin 12 tied to 0V?
     
  12. kurtruk

    Thread Starter Member

    Aug 26, 2012
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    Yes pin 12 is tied to GND
     
  13. tracecom

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    Apr 16, 2010
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    I have breadboarded an oscillator circuit using a CD4060 and I am getting a clock signal at pin 9, but haven't checked further yet. The signal at pin 9 seems to be the correct frequency (32 kHz) and is about 3Vpp with a 12V supply, but it has a 2V positive offset. I don't know it that is what it is supposed to have or not.

    I am using 1M and 100k for the resistors and 33pF for the caps.
     
  14. tracecom

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    Apr 16, 2010
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    I have put an LED with a 1k series resistor on pin 3, anode to pin 3 and cathode to 0V; it is flashing at what I guess to be 2 Hz. The voltage is 10 Vpp.
     
    Last edited: Jan 20, 2013
  15. kurtruk

    Thread Starter Member

    Aug 26, 2012
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    Ok, but I guess my real question is why doesn't my design work?
     
  16. tracecom

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    Apr 16, 2010
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    The RB and tubeguy have already made some suggestions; it could be one of those or it could be something else. Stray capacitance makes crystal oscillators behave in strange ways. For example, if I remove the 33pF caps and replace them with 10pF caps, my circuit stops oscillating. It could be that, despite your best efforts, you have a wiring error. It's possible you have a bad crystal; the first one I tried wouldn't oscillate. Maybe your LED is reversed or defective.

    What is your power supply voltage and what kind of power supply is it? Check to see if you can measure it directly across pins 16 and 8 of the 4060. Check to see if you can see the voltage on pin 3.

    If you have an oscilloscope, look at pin 9 and see if you see the base frequency of 32.768 kHz. If so, then look at pin 3 and see if you can see the 2 Hz.

    Post a closeup photo of your assembly top and bottom. Someone might be able to spot a problem area.

    Don't give up; you can make it work.
     
  17. tubeguy

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    Nov 3, 2012
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    Why not try experimenting with the values (one by one) that tracecom was so kind to provide .... :rolleyes:

    I've always learned the most by trial and error(s).
     
  18. kurtruk

    Thread Starter Member

    Aug 26, 2012
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    My power supply is roughly 5.2 Volts (measures with my multimeter) and is from 4AAs.

    I had a idea I absantly mindidly did not include bypass caps. Could that make a difference?

    I know my LED works.

    I have tried connecting a LED between the outputs of the 4060 and ground and have got a apparent solid on everyone. Does that mean the crystal is oscillating?

    P.S. Thanks for all your help.
     
  19. tracecom

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    Apr 16, 2010
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    You're welcome.

    With a battery supply, a bypass cap might not be needed, but it wouldn't hurt to add a .1 uF across the power pins.
    A solid lit LED on pin 3 means the circuit is not oscillating.

    Do you have spare parts, or are they all soldered together? Post some pics if you can.

    Here is a picture of my breadboard; maybe it will help in some way. You will notice that it is a solderless breadboard; despite some that some say it won't work, it does.

    ETA: Just for grins, I changed the value of R1 to 15 M, R2 to 330 k, C1 and C2 to 10 pF as shown in the Fairchild datasheet. The circuit continued to oscillate. Maybe when I tried those values earlier, I had a wiring error?
     
    Last edited: Jan 20, 2013
  20. tubeguy

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    Nov 3, 2012
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    You could try it using the RC oscillator to test the chip.
    Maybe a 10-22k for R1, 100-220k for R2 and .001uf. or something similar.
     
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