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CD74HC4059: Creating a Frequency Divider

Part Number: CD74HC4059

Hello again,

I posted here a couple of months ago regarding a frequency divider and you guys were a huge help, Emrys especially. 

What I Have:

I further developed the circuit to accept sinusoidal wave inputs and square wave inputs. If a sinusoidal wave in being used, the signal will first go through a comparator op amp to turn it into a square wave, then schmitt trigger, then to the frequency divider. If a square wave is used as the input, the user switches a jumper, and the signal now bypasses the comparator and goes directly to the schmitt trigger then to the divider. 

The Problem:

When using the square wave input with a square wave generator or a reed switch, the circuit works flawlessly - with the exception of a small delay. 

When using the sinusoidal wave input with this magnetic sensor (Digikey PN: 480-3911-ND), the circuit does not work so well. I have N = 10 in both cases, yet on this input, the frequency is divided by 9 most of the time. I'm not sure what is causing this to happen?

Any insight would be helpful. 

Thanks,

Gage

  


005875-2-EN Magnetic Sensor.pdf

CD74HC4059 24 pin.pdf

SN74LVC1G17 Schmitt Trigger Buffer.pdf

  • Hi Gabe,

    I was wondering if I can get scope shots from the input and output to the HC4059. This will help clarify where the issue is occurring.
    Also, you might want to try to let the sinusoidal signal bypass the comparator as well and directly feed into the schmitt trigger just like the square wave. This will help isolate the problem with this circuit.

    Thanks!
    - Karan
  • Hey Gabe,

    Did you find your problem? Please let me know if you need anything else from my end or I will go ahead and close this post.

    Thanks!
    - Karan
  • Hi Karan,

    I apologize for the delayed response, I took some time to do some testing of my own.

    I sent in a sin wave with the sin jumper connected and recorded the waveform before and after the divider (see pictures below).

    I sent the same sin wave in with the square wave jumper connected (bypassing the comparator) and got no response before or after the divider. 

    The first picture is a square wave which comes right after the Schmitt trigger and just before the divider IC. The second picture is after the divider IC.

  • Hey Gabe,

    You should lower the ouput load on the device. The .1F load is huge. The device is meant operate at maybe 15pF. Secondly, the design seems correct. Once you sine wave is converted to a square wave, is this square wave being correctly divided by 10 by the HC4059? It is very difficult to tell from your scope plots. If so, the problem might be in the comparator circuit. You can post on the op-amps group to ask if they see any problems with that. If the square wave is being divided correctly, the only reason I can think for this not to work is the comparator or that the input signal is flawed in some way.

    Thanks
    -Karan