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 Forum index » DIY Hardware and Software » Developers' Corner
4017 sequencer
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konolda



Joined: Oct 08, 2013
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Location: MN

PostPosted: Tue Oct 08, 2013 6:11 pm    Post subject: 4017 sequencer Reply with quote  Mark this post and the followings unread

Ok, so I am new to this subject. I have made a couple of speak and spells, oscillators and such but am not experienced by any means. I was thinking of building a low-fi sequencer to create sequences with simple 555 oscillators. But rather than having eight 555 circuits, could I patch 8 different potentiometers into the same oscillator using solid state relays driven from the 4017 outputs so I could have each step at it's own pitch? I understand the logistics of wiring this, but am not sure the response of the relays would keep up seamlessly with the 4017. Thoughts?

Thanks, Adam
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elmegil



Joined: Mar 20, 2012
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PostPosted: Tue Oct 08, 2013 9:50 pm    Post subject: Reply with quote  Mark this post and the followings unread

"Solid State Relays" are you talking CD4066? Or actual physical relays?

Here's a thread with a stripboard layout for a 4017 based sequencer which works:
http://electro-music.com/forum/topic-52774.html

In that thread there is also reference to Fonik's version of the same:
http://modular.fonik.de/pdf/baby10.pdf (there's a minor issue with the reset in circuit, let me know if you go that direction I can explain it).

Bottom line is, typically these designs use diodes to route the current rather than relays, but other than that follow your idea.
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konolda



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PostPosted: Wed Oct 09, 2013 6:12 am    Post subject: That makes more sense Reply with quote  Mark this post and the followings unread

Yes, that's the idea I was going for, although much simpler and more logical. Thanks for you help, appears I was making it harder than it needed to be(not that I am surprised).
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elmegil



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PostPosted: Wed Oct 09, 2013 7:10 am    Post subject: Reply with quote  Mark this post and the followings unread

If I had a dollar for every time *I* did that... Wink
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konolda



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PostPosted: Thu Oct 10, 2013 1:41 pm    Post subject: Control voltage Reply with quote  Mark this post and the followings unread

Ok, so now I have a new question(surprise surprise). I have always made basic 555 oscillators with a pot between pins 2 and 7 for pitch control. But I am not sure where I would tie in the control voltage output from the 4017 sequencer. Pin 5 of the 555 is control voltage(from what i can tell), but in circuits I have built so far, I always connected this to a cap connected to the ground. Long story short, I have no idea how to use a cv to modify pitch on a 555 oscillator. I was going to do this project before I got into using cvs but now I realize I just need to bite the bullet and learn this essential concept now. Thoughts?
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elmegil



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PostPosted: Thu Oct 10, 2013 2:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

The easy answer is a vactrol which is an LED and an LDR in a light-tight case. The brighter the LED, the lower the LDR resistance, voila instant voltage controlled resistance.

The problem with that approach is that good vactrols are expensive, and cheap vactrols are wildly variable in what their response curves look like. Maybe expensive ones are as well, I'm not deeply versed in vactrols.

I would recommend looking at some of Thomas Henry's recent 555 based circuits, notably he has a VCO that has a 555 at the core. He has his own subforum here, so if you go there and look for posts active over the last year (roughly) it should be easy to find.
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PHOBoS



Joined: Jan 14, 2010
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PostPosted: Fri Oct 11, 2013 3:06 am    Post subject: Reply with quote  Mark this post and the followings unread

A vactrol is an option, but yes you can also use pin 5 for that. the first sequencer VCO combo I made was actually exactly that Very Happy (see avatar)

I would suggest reading this page to learn more about the 555 timer, so you know why it does what it does.

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