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Simple CMOS clock generator and divider
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egasimus



Joined: Feb 11, 2011
Posts: 112
Location: Bulgaria

PostPosted: Wed Jul 17, 2013 9:47 am    Post subject: Simple CMOS clock generator and divider
Subject description: Anyone care to have a look? :)
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Hey guys, after taking a long break from never getting around to building anything, I took apart an old Soviet mixing desk on a whim and found myself with about a shitload of potentiometers. So I decided to build myself a step sequencer and wire it up to things. However, I realized I would need a clock generator to drive it, so I whipped up this design in an afternoon.

http://i.imgur.com/YgJggg8.png

Would anyone more experienced than me please spend a minute to have a look at it and tell me whether it'll fly? What I'm most concerned about is not really knowing where do I need to put pull-down resistors.

In case you're wondering, the whole S1 mess that you see near the top right is a single 2P6T rotary switch, wired to let me select between /3, /5, /6, /7, /9 and /10 modes for the 4018, as described in the chip's datasheet. And I just found a mistake in it - pins 11 and 12 should be wired together Very Happy
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piedwagtail



Joined: Apr 15, 2006
Posts: 157
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PostPosted: Sat Jul 20, 2013 4:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

This a prime case of breadboard! Empirical Studies.

Since it's modular in schematic each section can be whipped together and checked with a humble led.

You could use MML mickey mouse logic to avoid the 4081.Couple of diodes.

Or use the 4081 spares with cgs style comparators to gate the outputs. ie clock signal in one input; cv higher or lower than threshold to control the clock getting through: A latched switch will give you stop and start; an lfo intermittent timing without losing the pulse as it were.
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Dave Kendall



Joined: May 26, 2007
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PostPosted: Sun Jul 21, 2013 2:42 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi.

You might want to consider adding input protection to the 4024. It could be damaged with greater than 9V inputs from, say a modular.
Maybe consider an op-amp based comparator, which will square up the input to give a nice clock from almost any signal, and also protect against over and negative voltage.

The CGS07 has such a single-supply comparator - look at the top left two inputs. Simply swap the +15V shown for your +9V supply.

CMOS is great fun. Good luck with it!

cheers,
Dave

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beep



Joined: May 05, 2013
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PostPosted: Sun Jul 21, 2013 3:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

I wonder if there is a simple circuit, which can turn a very short clock pulse
or even better, a gate signal of any length,
into a gate signal of a variable length. 555 monostable multivibrator?

And how can I amplify the output signal of a standard soundcard or mp3 player (which will be clock pulses) to trigger e.g. a 4017 counter or a 4066 switch? I tried to amplify it with an op amp, but it works only if I boost the shit out of my M-Audio FastTrack Pro

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Cynosure
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PostPosted: Mon Jul 22, 2013 9:04 am    Post subject: Reply with quote  Mark this post and the followings unread

beep - You are kind of thread hijacking, but here are my thoughts:

Yes the 555 could do it. Use the short pulse as a trigger for a 555 envelope generator, but have no resistors where the attack pot usually goes. You can then square up the output by passing it through two schmitt invertors (one to square it up and the second to get it back to the correct inversion).

A schmitt invertor could also be used for audio issue. Pass the sound through it, and you only need to amplify it enough to pass the trigger threshold (usually just a bit higher than the halfway point between Vss and Vdd). If you still need more amplification then use a lm324 to boost it before going into the schmitt trigger. Then pass it through one more scmitt trigger to get the correct inversion. You might want to use protection diodes on the audio input just to make sure you don't damage anything.
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PHOBoS



Joined: Jan 14, 2010
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PostPosted: Mon Jul 22, 2013 12:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

Cynosure wrote:
beep - You are kind of thread hijacking, but here are my thoughts:

Yes the 555 could do it. Use the short pulse as a trigger for a 555 envelope generator, but have no resistors where the attack pot usually goes. You can then square up the output by passing it through two schmitt invertors (one to square it up and the second to get it back to the correct inversion).

no need for schmitt inverters,.. just use it in standard monostable mode:
pins 6, 7 are connected together with a resistor (and/or pot) to + and a cap to - (or GND). pin 3 your output and a high to low signal on pin 2
will trigger it.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

If you do it like this and your input pulse is longer then you want your output pulse to be it won't work,. but you can fix this by adding a capacitor
in series with pin 2 (you will also need to add a pull up resistor to pin 2). If you also add an inverter to the input (can be done with a transistor), it will
trigger on a standard low to high transition.

For the audio to pulse conversion you could use a comparator, which has the advantage that you can adjust the trigger level. (you could make
it inverting too in case you want to attach it to the monostable 555), or lookup tim escobeda's PWM Cool

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prgdeltablues



Joined: Sep 25, 2006
Posts: 172
Location: UK
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PostPosted: Tue Jul 23, 2013 6:43 am    Post subject: Reply with quote  Mark this post and the followings unread

OP - have you looked at Yusynth's clock divider - seems to do what you are after.

http://yusynth.net/Modular/index_en.html



Beep - have a look at the Tellun Gate Processor: 555 based variable length gate outputs:

http://tellun.com/motm/diy/tln866/TLN-866.html


Peter
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egasimus



Joined: Feb 11, 2011
Posts: 112
Location: Bulgaria

PostPosted: Thu Jul 25, 2013 3:57 am    Post subject: Reply with quote  Mark this post and the followings unread

Weird, I though I had posted a reply last night... Can't find the pic I uploaded in my imgur, either. Paranormal stuff...

Anyway, doing this with a 4017 makes so much more sense! I entered the schematic for a single divider into Eagle with the intention of making a stripboard layout for it. Can anyone tell me whether it would care much for power supply voltage? Cuz I intend to run it off 9V or 5V instead of 10/12/15, at least for the time being...

Posted Image, might have been reduced in size. Click Image to view fullscreen.
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beep



Joined: May 05, 2013
Posts: 84
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PostPosted: Thu Jul 25, 2013 4:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

hey peter, thank you very much!!! Smile
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