Octave up 4046 PLL doesn't work

[yanusch]

Hello you all,

I am trying to get an octave up using a 4046 pll instead of rectification,
From my understanding the schematic i made should work with a divider between the vco_out and the comparator_in.

The signal i feed in is a squarewave from a function generator so not a squared up guitar signal so the input is as clean as it can get i suppose.



Can somebody spot something wrong with it?

Ps. the only thing i get out is a really high pitched squarewave even without the function generator attached? This can't be good i suppose.

Thnx
Yanusch

[anotherjim]

You need to use the counter Reset pin. As it is, it always counts to maximum. Off the top of my head, I think you need Q2 connected to reset.
So after reset, Q0 will be Hi. Next clock Q1 is hi & Q0 low. Next clock, Q2 goes hi but immediately causes reset and it's back round to Q0 Hi.
I'm not sure it's practical to have /1 with the counter, you would switch COMP_IN directly to VCO_OUT for /1 and switch out the counter using a SPDT switch.

You'll be able to get odd numbered multiples from that counter if you have a rotary switch giving reset from a choice of Q2 through to Q7, but of course at stupidly high frequencies. So you put another counter on the output to divide them down again.

[yanusch]

Thnx jim (again! it seems that every post that i do you have an answer to it, what are you a guru or something  )

That makes sense that it always has that high square wave going out.

So if i understand it correctly connect the reset pin to Q2 instead of ground?
The divide bij 1 / 2 is a mistake this must be 2 and 4 of course.

[yanusch]

Hmm i tried connecting the reset pin to q2 but it doesnt work

if i feed the signal generator directly into pin 1 from the 4024 as on the schematic (so with reset to ground) it divides good. So i suppose that couldn;t be the problem then? Pin 12 divides by 2 and pin 11 by 4

[slacker]

It could be your filter values, try 470k to 1M for R8, 100k for R7 and 220n to 470n for C8 and 1k for R6, I've built a couple of things using those sort of values for guitar frequency stuff. Nice cut and pasting 

[anotherjim]

Counter seems to be behaving itself.
Guru? More like been there before

Agree with Ian about component values.
Add that I've found C4 better somewhere 1nF to 10nF

I've never had faith that you can arrive at suitable values for the 4046 just from either calculations or reading off the graphs in the data sheet. I'd have variable resistances added in series with R6 & R8 - those 10K's should stay in series for a safe minimum.

Without the divider and a straight loop connection instead. Does it lock onto the sig gen? Does it still lock on if you double the sig gen frequency?
When you want frequency multiplying, you want the VCO to run faster, so C4 & R6 must suit the higher VCO frequency.

R7 makes it a lag/lead loop filter. It reduces warble while chasing a new frequency (Theremin sound!), but can make it jittery instead. I'd leave it out to start with to keep the problem simple.

[yanusch]

Hmmm, i changed R6 to 1K and C4 to 10nf, when i close the loop (so connect pin 3 and 4) the 4046 doesn;t lock to the frequency from the generator no matter what frequency i put into it (i've done a sweep from 0.0005hz to 5khz, the entire range of my generator)



Here is a picture of my breadboard mayby i connected something wrong?

[slacker]

Your connections to pins 5 and 12 don't look right and don't match your schematic. Pin 5 should be grounded, pin 12 should be connected to nothing and there should be a resistor from pin 11 to ground.

[anotherjim]

You can see a working 4046 octave shift at...
http://www.parasitstudio.se/building-blog/upcoming-project-into-the-unknown
...but I think you need to log in to their forum at Madbean.

[yanusch]

Thnx slacker i indeed made a mistake while breadboarding, weird thing that even after checking it 3 times that you can still make stupid mistake by simply miscounting the pins.

So finally the pll is giving the same output as the input feeding into it, but if i open te loop again and put a divider in between it still gives the same output frequency as the input frequency, it doesn't multiply. Any thoughts on that?

[yanusch]

Nevermind probed te wrong pin (pin3) out of pin 4 is now coming a multiplied frequency 

topic closed thank you guys

ps. anotherjim: the 4046 part of the schematic is actually from parasitstudio from the 0415 guitar synth, but he divides it with a 4015 but i only had a 4024 flipflop lying around

[thehallofshields]

Cool circuit. Can it use Q1 - Q7 on the 4024 Divider?

[anotherjim]

Well, since its xmas & all that, I'll try to answer before I hit the beer & vodka

You can in principle have any division ratio in the loop. Octal/decade counters can get you odd numbered ones too.
The VCO range setting R & C might need tweaking so the VCO CV isn't too close to 0v or +supply volts to make sure it can track with wiggle room.

[thehallofshields]

Thanks Jim, Merry Christmas to you.

So you're saying R8 and C8 are creating a LPF, but for what purpose?

I need the 101 on PLL's. Can anyone recommend one?