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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
Frequency multiplier / melody generator.
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SUGARAT



Joined: Jan 21, 2015
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Location: California
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PostPosted: Thu Jan 22, 2015 6:36 pm    Post subject: Frequency multiplier / melody generator.
Subject description: Any help with new module?
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Hello!
I've been working for about a month on a module that works as a basic " melody generator" except that it multiplies the incoming frequency instead of dividing. It uses a 4046 pll with a 4017 in the loop as seen on schematics here as well as forest mims, I believe. Which of the a outs is routed to the reset pin is determined by a 4051 mux. So the input is multiplied by a number from 1 to 8 determined by the logic states of the 3 control inputs.

I wired it all together and THOUGHT it was working fine until I tried running it's out into another counter and realized that, although it works fine when plugged into my mixer, the output won't drive another cmos input Embarassed I've tried so many things. Each chip has .1uf decoupling cap and the board has it's own 10uf. I tried buffering the output and that didn't work either. I am starting to suspect that the problem has something to do with the "Special Considerations" mentioned in the 4051 datasheet. A drop in voltage is causing current to flow from the switch to pin 3?
Is there a way to check if this is what is happening? If it is, how would I fix it?

Anyway, like I said, it DOES work when the output is sent to a mixer and it sounds really cool! Like a melody generator with a bit of portamento and filtering. You know now it is with that 4046 Twisted Evil
I'll post samples if I come across decent wifi
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PHOBoS



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PostPosted: Thu Jan 22, 2015 7:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

try a pullup resistor of 4K7 connected to the reset pin of the 4017, assuming it's also connected to pin 3 of the mux.
I ran into a similar problem when I made my chromatic melody generator so that might solve it.

oh and welcome party!

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SUGARAT



Joined: Jan 21, 2015
Posts: 19
Location: California
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PostPosted: Thu Jan 22, 2015 10:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

thanks!
I was thinking something like that might help pull current through or something. Unfortunately it didn't work. Messed with several values. Signal just gets quieter.


One thing I noticed is that if i remove the pulldown resistor on the in (pin 14) of the 4046 the signal sounds really noisy yet it solves the problem of other chips not being able to read the signal as long as all control inputs on the 4051 or low. if any are raised while the output is running into another chip the circuit stops working and wont function again until i plug a jack into the out on pin 2 and then back to pin 3. Weird.
I'm running this circuit and a bunch others off of a 9v wallwart, by the way. not sore if that helps.
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SUGARAT



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PostPosted: Fri Jan 23, 2015 7:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

AH!
but the reset of the 4017 is ALSO connected to pin 3 on the 4046. Could this be why that pull up resistor didn't work? perhaps these three pins being tied together is the problem. What if I run pin 2 of the 4017 into the comparator input instead...

ugh. still doesn't work.
Maybe a diode?
Maybe my 4046 is busted. I'll order some new ones and if that doesn't work I guess I'll just do a redesign and replace the 4017 and 4051 with 4018 Rolling Eyes
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synaesthesia



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PostPosted: Sat Jan 24, 2015 1:58 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi SUGARAT and welcome! Maybe it helps if you show us your schematic with the actual values.
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SUGARAT



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PostPosted: Sun Jan 25, 2015 4:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

I think that is everything minus the decoupling caps on each chip and pull down resistors on the control ins. Sounds cool but still not quite working for me.

A pull down resistor should be placed on the input for stability but omitting it does add a nice distortion effect.
Replacing R1 with a 500k pot also adds some gunk.
When I first wired it up i had pin 3 of the 4046 going to pin 3 on the mux and also a toggle switch to disconnect the 4017 so other signals could be patched in but I undid all that and simplified it to this configuration at least while trouble shooting.


FREQSYNTH.png
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FREQSYNTH.png


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SUGARAT



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PostPosted: Sun Jan 25, 2015 7:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

And here's a lil taste of the WIP


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SUGARAT



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PostPosted: Tue Jan 27, 2015 11:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

And here's how it sounds. at first just sending LFOs to ABC then tweaking R1. right at the end LFOs are speeded up to audio rate.


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synaesthesia



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PostPosted: Wed Jan 28, 2015 1:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi SUGARAT, I tried your schematic with different values (10nF hardwired on my board for C2), but couldn't get the PLL to lock properly most of the time using PC2_OUT. PC1_OUT worked better for me. So I cannot comment on the multiplication. However, I never saw any issues with the output signals on the scope. Maybe it is the combination of the diode in your output path and the mixer. In the schematic pin 13 (CLK_EN) of the 4017 should go to Vdd of course.
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SUGARAT



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PostPosted: Wed Jan 28, 2015 6:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for trying it out! The datasheet I am looking at says that pin 13 is clock inhibit. the clock is enabled when it is low.
I haven't tried switching out c1 much.Maybe a couple values didn't notice much change. When you say phase comp 1 worked better, do you mean you placed r1 between 9 and 2 instead of 13? That I haven't tried.

I got a lot of help in the chat. I think my problem has something to do with my PSU. Everything works fine if i remove the 4051 and reset the 4017 with a wire instead. I'm just going to make a simpler module with just a 4046 and in and out jacks in the loop and then work on building a better power source. Maybe turn this circuit into a tiny syth of its own.
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synaesthesia



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PostPosted: Thu Jan 29, 2015 1:00 am    Post subject: Reply with quote  Mark this post and the followings unread

You are right, the data sheet I have says CLOCK ENABLE, but the description points out that it is negative logic and needs a 0 to enable Confused Didn't notice that because I was using a divider that had the input already connected.

I tried R1 between 2 and 9, and had a much smaller R2 of 1K. I believe PC2 should work better, but I didn't in my case. I was using Vdd of 5V.

Is anybody aware of an online calculator for the 4046?
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elektrouwe



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PostPosted: Thu Jan 29, 2015 2:55 am    Post subject: Reply with quote  Mark this post and the followings unread

SUGARAT wrote:

...t if i remove the pulldown resistor on the in (pin 14) of the 4046 the signal sounds really noisy yet it solves the problem of other chips not being able to read the signal as long as all control inputs on the 4051 or low...


I don't know if this is a part of your problem, but when I read "4046 pin 14"
I remembered a warning on this page ( german language, sorry)
http://www.elektronik-kompendium.de/public/schaerer/pll4046.htm
basically it says pin 14 is not a digital input and it needs proper biasing, else the 4046 (4000 and 74HC series) can un-lock. The cure was generating VDD/2 with a 10k/10k voltage divider and feed the signal via another 10k resistor ( see picture "Bild 8" )
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SUGARAT



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PostPosted: Thu Jan 29, 2015 10:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Wow thanks electrouwe!
Whether or not this relates to the problem it is good to know. I've noticed this input doesn't behave like other CMOS inputs. When checking my other 4046 module I noticed that I didn't add a pull down resistor to its input. I can't remember why I left it out but I really doubt I forgot. I must have decided that it worked better that way. Perhaps a gain control on the input is worth adding to 4046 circuits? I'll experiment.
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