electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links
Forum with support of Syndicator RSS
 FAQFAQ   CalendarCalendar   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   LinksLinks
 RegisterRegister   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  Chat RoomChat Room 
 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
40106 oscilator stability?
Post new topic   Reply to topic Moderators: mosc
Page 1 of 1 [9 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
commathe



Joined: Jul 26, 2013
Posts: 153
Location: Beijing
Audio files: 5

PostPosted: Fri Jul 26, 2013 5:23 pm    Post subject: 40106 oscilator stability? Reply with quote  Mark this post and the followings unread

Hey everyone. I've been a long time lurker here and I've decided to bite the bullet and stop making stompboxes and start on a Lunetta style modular.

Breadboarding away last night though I came across a weird phenomenon. When I ran the 40106 on 4.5v it behaved very well and all 6 oscillators were very stable. On 9v however they wobbled really irregularly between two close pitches. What could have been causing this? I actually really liked the effect and when I build a module I kind of like the idea of being able to make an oscillator less stable at the turn of a dial.

Is it possible that the resistors I used to sum the signals together weren't big/high enough to hold back the current under 9v but were under 4.5v?
Back to top
View user's profile Send private message
PHOBoS



Joined: Jan 14, 2010
Posts: 5591
Location: Moon Base
Audio files: 705

PostPosted: Sat Jul 27, 2013 2:39 am    Post subject: Re: 40106 oscilator stability? Reply with quote  Mark this post and the followings unread

interesting, you might be right about the resistors. I don't know what value you used but if they are low then it could cause some instability.
and/or maybe you used a 9V battery that was a bit empty.

If you want to create instabillity you can do this by adding a starve pot, which will let you limit the current, causing irregular behaviour.

_________________
"My perf, it's full of holes!"
http://phobos.000space.com/
SoundCloud BandCamp MixCloud Stickney Synthyards Captain Collider Twitch YouTube
Back to top
View user's profile Send private message Visit poster's website AIM Address Yahoo Messenger MSN Messenger
commathe



Joined: Jul 26, 2013
Posts: 153
Location: Beijing
Audio files: 5

PostPosted: Sat Jul 27, 2013 2:45 am    Post subject: Reply with quote  Mark this post and the followings unread

The resistors were 100k and the battery was new. Running them off 4.5v was actually off the same battery. I have a power module thingy I made so I didn't have to do voltage dividers every time that I wanted to use an op amp!

I tried voltage starving too, but the results were different. Very fun in a different way. I have a 100uf cap on my power module which meant that I got some very fun effects from unplugging the battery.
Back to top
View user's profile Send private message
Cynosure
Site Admin


Joined: Dec 11, 2010
Posts: 966
Location: Toronto, Ontario - Canada
Audio files: 82

PostPosted: Sat Jul 27, 2013 9:34 am    Post subject: Reply with quote  Mark this post and the followings unread

Here are several pieces of advice:

1. Always run CMOS chips from a power regular if possible. Running them directly from a battery can cause stability issues, especially as the battery power gets low.

2. Always use bypass caps on EVERY chip. Use a 0.1uF cap and plug it is as close as possible to the Vdd and Vss pins. This will smooth out any power fluctuations in the power supply that is being delivered to the chip.

3. Choose your oscillator caps wisely. Some are better suited than others for oscillators. http://www.analogrules.com/capacitors.html

_________________
JacobWatters.com
Back to top
View user's profile Send private message
commathe



Joined: Jul 26, 2013
Posts: 153
Location: Beijing
Audio files: 5

PostPosted: Sun Jul 28, 2013 2:27 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the advice! Though to clarify, do you mean that I should join Vdd to Vss with a cap - or rather that I should use a two caps (one for Vdd and one for Vss)?
Back to top
View user's profile Send private message
Cynosure
Site Admin


Joined: Dec 11, 2010
Posts: 966
Location: Toronto, Ontario - Canada
Audio files: 82

PostPosted: Sun Jul 28, 2013 9:50 am    Post subject: Reply with quote  Mark this post and the followings unread

You should join Vdd and Vss with a cap that is as close to the Vdd pin as possible.
_________________
JacobWatters.com
Back to top
View user's profile Send private message
commathe



Joined: Jul 26, 2013
Posts: 153
Location: Beijing
Audio files: 5

PostPosted: Sun Jul 28, 2013 7:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

Awesome, thanks!
Back to top
View user's profile Send private message
Cynosure
Site Admin


Joined: Dec 11, 2010
Posts: 966
Location: Toronto, Ontario - Canada
Audio files: 82

PostPosted: Sun Jul 28, 2013 7:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

You're welcome. More info on bypass caps here:

http://www.seattlerobotics.org/encoder/jun97/basics.html

You should use them on every IC.

_________________
JacobWatters.com
Back to top
View user's profile Send private message
JingleJoe



Joined: Nov 10, 2011
Posts: 878
Location: Lancashire, England
Audio files: 14

PostPosted: Tue Aug 06, 2013 3:12 am    Post subject: Reply with quote  Mark this post and the followings unread

I've found that even on a good power supply the oscillators can interfere with each other within the IC.
My thinking would be don't use a 40106 for precise stability. general stability, probably good but with multiple oscs on the IC you can have frequency locking problems if the feedback resistance is low.

_________________
As a mad scientist I am ruled by the dictum of science: "I could be wrong about this but lets find out"


Green Dungeon Alchemist Laboratories
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic Moderators: mosc
Page 1 of 1 [9 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


Forum with support of Syndicator RSS
Powered by phpBB © 2001, 2005 phpBB Group
Copyright © 2003 through 2009 by electro-music.com - Conditions Of Use