Troubleshooting Phase Locked Loop Circuit with 3 ICs

[MissP.25_5]

Hello,
I am in need of big help here. I don't know what else should be done to get this correct.
I have to build this PLL circuit and choose any 3 N (integer) of the N-divider. Then I have to observe the input signal Sig_in and the output signal VCut for each N. The result should be that the output frequency is N+1 times bigger than that of the frequency set by ELVIS (function generator), if I have understood the instructions correctly. I attached my results. The output signal looks weird, right? When I set N as 1, the output signal gets messed up :/ I tried for N= 4 and 8, the waveform looked just the same as when N=1. What should I do? By the way, where should I connect the 5th pin of IC 85 (A=B) to? In the diagram it just shows a short line not connecting to anything.

I took 4 pictures of different angles so you can see better. Click on the flickr links to see the pictures of my circuit.

NOTE: THE DIAGRAM IS IN THE PDF FILE PAGE 2.

http://www.flickr.com/photos/98820721@N04/11870437296/sizes/o/in/photostream/

http://www.flickr.com/photos/98820721@N04/11870033074/sizes/h/in/photostream/

http://www.flickr.com/photos/98820721@N04/11870445586/sizes/k/in/photostream/

http://www.flickr.com/photos/98820721@N04/11869882813/sizes/k/in/photostream/

 

[NascentOxygen]

Hi MissP. Can you attach a jpeg showing the schematic of your circuit? (I don't do pdfs.)

 

[MissP.25_5]

Hi MissP. Can you attach a jpeg showing the schematic of your circuit? (I don't do pdfs.)

There you go!

 

[NascentOxygen]

The first step is to understand the function of each chip, so that you are able to then judge whether each is performing as expected. What do you understand is the function of the 393 chip? What does it do here?

 

[MissP.25_5]

The first step is to understand the function of each chip, so that you are able to then judge whether each is performing as expected. What do you understand is the function of the 393 chip? What does it do here?

The 393 chip serves as a counter. The 74hc393 counts only until the output count equals the setting of the ELVIS switches, I think. If you have A>B line connected to 74hc4046, then you have an output every time A>B.

 

[NascentOxygen]

First, we should check that the free-running frequency of the VCO is close to the designed value. Disconnect the wires from pins 14 and 3 of the 4046, and measure the frequency of its output (pin 4). Is this frequency close to what you were hoping for?

Did you design for a particular free-runnng frequency, or are you just using values for external R's and C's that you have been told to use?

 

[MissP.25_5]

First, we should check that the free-running frequency of the VCO is close to the designed value. Disconnect the wires from pins 14 and 3 of the 4046, and measure the frequency of its output (pin 4). Is this frequency close to what you were hoping for?

Did you design for a particular free-runnng frequency, or are you just using values for external R's and C's that you have been told to use?

I am just using values for external R's and C's that I have been told to use. What difference does that make? I actually run a VCO test before and here's the results.

Left side is V, right side is kHz. I have set the frequence between this range but I still didn't get the result I am hoping for!

 

[NascentOxygen]

When you have measured the free-running frequency, let me know what it is.

Also, what frequency Source Clock are you applying to pin 14 of the 4046? You attached 2 schematics,, identical except for that frequency.

 

[MissP.25_5]

When you have measured the free-running frequency, let me know what it is.

Also, what frequency Source Clock are you applying to pin 14 of the 4046? You attached 2 schematics,, identical except for that frequency.

How to check the free-running frequency? I set the reference frequency to 4kHz.

 

[NascentOxygen]

How to check the free-running frequency?

See post #6

I set the reference frequency to 4kHz.

Is that what is labelled Source Clock? Disconnect it, and disconnect other feedback, and the 4046 should oscillate by itself at its free-running frequency.

BTW, I'm curious to know what your lab instructions say is the goal of this demonstration? Can you quote what the notes say?

 

[MissP.25_5]

See post #6


Is that what is labelled Source Clock? Disconnect it, and disconnect other feedback, and the 4046 should oscillate by itself at its free-running frequency.

BTW, I'm curious to know what your lab instructions say is the goal of this demonstration? Can you quote what the notes say?

Oh, sorry I missed post no.6.

Yes, that's the source clock.

The goal is to get the frequency of this circuit, that is "frequency from ELVIS x (N+1)" even if the waves are not fully locked.

 

[NascentOxygen]

Yes, disconnect from pin 3. Remove the function generator by pulling the wire from pin 14 (that's 14, not 4). Does the 4046 oscillate, if so, what is its frequency?

Does the blue wire from pin 4 go anywhere?

Do you have this board at home, or do you have to wait until you next go to school/college/uni before you can test changes to the setup?

 

[MissP.25_5]

Yes, disconnect from pin 3. Remove the function generator by pulling the wire from pin 14 (that's 14, not 4). Does the 4046 oscillate, if so, what is its frequency?

Does the blue wire from pin 4 go anywhere?

Do you have this board at home, or do you have to wait until you next go to school/college/uni before you can test changes to the setup?

Yes, 14. I mis-wrote that. I don't have the board at home which is a big problem for me so I can't do any changes to the board yet. However, I did a VCO test before by connecting pin no 9 to the variable power source that ranges from 0 to 4 V. The frequency range at 0~4V was 289~528kHz

 

[NascentOxygen]

There were 3 questions in my last post. Please address all.

In post #1 you attached two pics. Can you explain where these signals were found, what you don't like about them, and what you expected they would/should be.

 

[MissP.25_5]

Yes, disconnect from pin 3. Remove the function generator by pulling the wire from pin 14 (that's 14, not 4). Does the 4046 oscillate, if so, what is its frequency?

Does the blue wire from pin 4 go anywhere?

Do you have this board at home, or do you have to wait until you next go to school/college/uni before you can test changes to the setup?

1. I haven't done that yet because I don't have the tools now. But doesn't the VCO test mean anything here? The result from the VCO test is in my previous post.

2. Yes, it is the VCO output to channel 2, it is also connected to Clock

 

[NascentOxygen]

In post #1 you attached two pics. Can you explain where these signals were found, what you don't like about them, and what you expected they would/should be.

Also, what factor were you dividing by when the pics were taken?