electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Articles  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links  |  Store
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
synthmonger vc-resistor
Post new topic   Reply to topic Moderators: jksuperstar, Scott Stites, Uncle Krunkus
Page 1 of 1 [7 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
jnuaury



Joined: Feb 28, 2008
Posts: 161
Location: chicago
Audio files: 9

PostPosted: Sat May 15, 2010 9:43 am    Post subject: synthmonger vc-resistor Reply with quote  Mark this post and the followings unread

anybody get this working nicely?

i found the schematic in a folder on my computer but did a search and found it posted in this thread http://electro-music.com/forum/topic-29678.html

my breadboard attempts have come out a bit wonky they seem to just "switch on" at a certain voltage and then dont have much variation after.
ive tried a few different diodes as i dont have any 1N914s
when i put a cap from the inverter input to ground i can get the 40106 to function as a VCO so i think my problem is with the 4016 or maybe the diode


vc_resistor_203.png
 Description:
 Filesize:  28.36 KB
 Viewed:  396 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

vc_resistor_203.png



_________________
az/gde
Flickr
YouTube
Back to top
View user's profile Send private message AIM Address
JovianPyx



Joined: Nov 20, 2007
Posts: 1988
Location: West Red Spot, Jupiter
Audio files: 224

PostPosted: Sat May 15, 2010 12:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

Is this your design? I looked at the other thread, but I didn't see a reference to this schematic. I think I see what it's trying to do, but the region of control will likely be very narrow due to the gain properties of CMOS gates.

Note that by design, the 4016 and 4066 are _switches_, not variable resistors. They are meant to behave as you described.

For inline resistors that can be controlled by a voltage (or current) see H11F1, H11F2 and H11F3. These are opto isolator devices in which an internal LED illuminates a CMOS transistor, the amount of light (controlled by the current through the LED) controls the resistance. See the datasheets for the resistance range.

_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
richardc64



Joined: Jun 01, 2006
Posts: 676
Location: NYC
Audio files: 26

PostPosted: Sat May 15, 2010 1:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

JovianPyx wrote:
Is this your design? I looked at the other thread, but I didn't see a reference to this schematic. I think I see what it's trying to do, but the region of control will likely be very narrow due to the gain properties of CMOS gates.

Note that by design, the 4016 and 4066 are _switches_, not variable resistors. They are meant to behave as you described.


It's on the second page, and is a fragment of synthmonger's 40106 VCO which, by all accounts, works. It's supposed to be a switched resistor, similar to switched capacitor circuits. It would seem to need a real resistor of 1K or so in series with the switch but frankly, I don't see how a variable switching rate translates to a variable resistance. I'd opt for a varying duty-cycle.

Edit:...unless the transistor at the 40106 input messes with the schmitt triggering thresholds, producing a variable width pulse Question

_________________
Revenge is a dish best served with a fork... in the eye
Back to top
View user's profile Send private message Visit poster's website
JovianPyx



Joined: Nov 20, 2007
Posts: 1988
Location: West Red Spot, Jupiter
Audio files: 224

PostPosted: Sat May 15, 2010 1:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ah, thanks richardc64. Now it makes more sense. When I looked at it, I thought "chopper" as in a switched capacitor, but he called it a voltage controlled resistor so I thought he was trying to control the analog switch to have steady state variable resistance controlled by a voltage. The H11Fx ICs I mentioned will do that.

Yes, high speed on and off switching can emulate a variable resistor, but only for charge/discharge of a capacitor. And yes, PWM (or duty cycle as you say) usually works best in that case.

If this were applied to resonance of a SVF or other multipole filter, I think filter Q modulation would result - I have no idea how that would sound - but who knows, it might be interesting, especially if you control the chopper's frequency.

_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
mistercooper



Joined: Jul 17, 2006
Posts: 62
Location: Seattle

PostPosted: Sun May 16, 2010 11:58 am    Post subject: Reply with quote  Mark this post and the followings unread

Try a vactrol or OTA. The 13700 datasheet has examples for floating vc resistors IIRC.
Back to top
View user's profile Send private message
synthmonger



Joined: Nov 16, 2006
Posts: 578
Location: flada
Audio files: 3

PostPosted: Mon May 17, 2010 5:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

What are you trying to use the vcovr with? Any switching diode should work fine. I'm 100% the schematic is working fine.

If you build it correctly and use a multimeter across the 'switch' pins you'll get a resistance from 0-500k, which is why I call it a voltage controlled resistor. Oh and use a couple .1uf caps across the power rails and don't forget to ground the unused inverters.

I've used these in place of things that would normally require a variable resistor or an OTA with success, (wasp filter, state variable filters, phase shifters, etc).

_________________
Youtube!
modular demos!
Whacky tunes!
Back to top
View user's profile Send private message Visit poster's website
e1999



Joined: Apr 25, 2019
Posts: 27
Location: naples

PostPosted: Mon Sep 07, 2020 5:23 am    Post subject: Reply with quote  Mark this post and the followings unread

Was wondering if anyone has used this with single supply rather than +-12v as shown in the schematic??
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic Moderators: jksuperstar, Scott Stites, Uncle Krunkus
Page 1 of 1 [7 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
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