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[SOLVED] [MOVED] Digital Project Help

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Thanks for getting back to me on this wonderful Friday!

This is what happens when the frequency counter is connected, it displays (---) No frequency :???:
It's weird because no matter where I connect the frequency counter on the circuit, the frequency is non existent... At least that what the frequency counter displays.. just no frequency..

17902842_10212898969091998_1067669926_o.png

Yikes...

Gentem
 

What is pin 9 of the CD4060 connected to? It's off the edge of the screenshot so I can't tell. It should be left disconnected, its the 'raw' clock signal prior to the divider chain so if you load it down it might prevent the dividers operating. If you disconnect it from wherever it goes and measure the frequency on it you should get 32768Hz.

Brian.
 
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    Gentem

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I've added probes to pretty much everything around the divider circuit, there definitely is plenty of activity from it..

17949953_10212904879679759_1291863601_o.png17949843_10212904913720610_552376658_o.png
 

Woooaaaahhhh......

those frequencies are completely wrong and so high that the CD4060 has no chance of operating. The schematic looks OK so I guess the simulation is at fault or isn't configured correctly.

You show 318MHz at the crystal but it should be 0.032768MHz !
The 4060 can count up to about 15MHz maximum so that would account for no ouput from it. I do not have Multisim (I don't think it runs under my OS) but if there are settings for the oscillator components see if you can adjust them so it gives 32.768KHz on pins 9, 10 and 11. If that doesn't work, you may be forced to trick the simulation by adding another clock source module directly to pin 11. That should fix the simulation but in real life the schematic as shown should be OK.

Brian.
 
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    Gentem

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I've created the 4060 circuit on it's own to check if 2Hz is being output, but nothing again... :?:


17968163_10212905482854838_1468635391_o.png
 

The "D(freq):" boxes should say 32.768KHz not 112MHz. I think Multisim is ignoring the crystal and only using the parasitic inductance and capacitance to calculate the frequency. In real life it should work but that doesn't help you at the moment. Try removing R25 and replacing it with a link to see if that makes it work, if not, the only other solution I can think of is to add a signal generator and inject 32.768KHz directly into pin 11.

If this is a only a project and not going to be built, it should be acceptable to explain that the Multisim failed to recognize the circuit and you had to fake the clock source, If you are going to build this, it should work as designed anyway.

Brian.
 
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    Gentem

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Besides R25 might be a bit high ohmic, but there are two basic questions:

- are you sure that the Multisim 4060 model includes analog modeling of the oscillator circuit
- simulation of crystal oscillator circuits is generally difficult due to the high Q, it rarely works without special prerequisites
 
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    Gentem

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I've attached a function generator and set it to 2000 Hz directly into the input of 4013 to try and make it as simple as possible for the time being, at least for the simulation part. I will have to build it also a few days before my deadline due to no lab access... Hopefully will have enough time to wire it all up :lol:

So having the 2000 Hz input in the 4013 should make it work, and actually it does, kind of, the AND gate that I've got that takes in the 4013's output of 1Hz and the main input frequency that I want displayed.. Outputs into the first LS90 but it switches between HIGH and LOW very fast and again, the only numbers that are being displayed are 4's, 8's and 0's...

It seem to "jump" count from 4 straight to 8 in each display and then it would reset and do the same.

Maybe I've got the LS75's wired incorrectly?

17976136_10212906953811611_938890786_o.png17968722_10212906958811736_1774969015_o.png17950112_10212906959811761_815452390_o.png17917013_10212906956851687_997438374_o.png
 

No, that's quite normal, what you are seeing is your input frequency being chopped up by the reference clock, the result is the numbers jump according to the ratio of the frequencies. However, 2KHz is far too high for the clock, remember you are trying (at least for now) to generate a gate period of one second and as it will be a square wave from the flip-flop, it needs to be at 0.5Hz (one second gate on, one second gate off). As you are dividing by 4 in the CD4013, your 2000Hz should be 2Hz.

There is a final stage to the project, that is to sequence the gate, latch and reset signals correctly. You need to reset the counters, gate 1 seconds worth of input frequency to the counters then latch their contents to the display.

Brian.
 
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    Gentem

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Would it not work to have the switches as they are now? That way frequency can be paused at any moment rather than every 1 second, that's what I understand?

Sequence:

1 Second worth of frequency is input
The 4013 input is high

Reset Switch remains at 1 (closed)
Latch remains at 1 (closed)

4013 input is low

Reset switch is 1 (closed)
Latch turns to 0 (open)

Display is frozen until user presses reset switch
Process then repeats

That's my understanding of a sequence for the circuit.

Gentem
 

It will work at the moment but you have to manually reset it before another frequency can be measured. If the sequence is automated it will give a continuous readout and show the input frequency 'live' and changing as the frequency is adjusted. Normal frequency counters do the latching and resetting automatically although some have an additional manual 'hold' control that prevents the latch updating.

Brian.
 

Hi,

I would like to thank you all for helping me on my project, tomorrow is the deadline and I have had it printed and built on PCB and is working exactly as it is supposed to be.



Couldn't have done without the help from this wonderful forum! :-D

Cheers

Gentem
 

Not a single bypass cap visible on the board?
 

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