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
Simple LED flasher circuit for vactrol pitch LFO?
Post new topic   Reply to topic Moderators: jksuperstar, Scott Stites, Uncle Krunkus
Page 1 of 1 [8 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
gmeredith



Joined: Jun 28, 2006
Posts: 82
Location: Tasmania, Australia
Audio files: 1

PostPosted: Wed Jun 28, 2006 5:25 pm    Post subject: Simple LED flasher circuit for vactrol pitch LFO? Reply with quote  Mark this post and the followings unread

Hi,
I'm a newbie looking to add a pitch vibrato to my bent Casio SK1 via a vactrol resistor. I need a simple LED flasher circuit that can flash from 1 flash/second up to about 20/second. All the 555 circuits i've seen only seem to flash slow (up to 2/second). Does any one know of one?

Thanks for your help, great forum

Cheers, Graham
Back to top
View user's profile Send private message
Scott Stites
Janitor
Janitor


Joined: Dec 23, 2005
Posts: 4127
Location: Mount Hope, KS USA
Audio files: 96

PostPosted: Wed Jun 28, 2006 10:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hey Graham,

You should be able to get a cap value on a 555 circuit to get a faster flash rate on a 555 (in this case, if you're running off of battery, I'd suggest a 7555, which has a mere fraction of the current draw a 555 has).

If that doesn't do the trick, a simple op amp LFO driving the LED might work, but I suck at single supply circuits - the Uncle K-man might have some good suggestions. Plus he might have a better grip on any coriolis related issues for down under Very Happy

Cheerio,
Scott
Back to top
View user's profile Send private message
gmeredith



Joined: Jun 28, 2006
Posts: 82
Location: Tasmania, Australia
Audio files: 1

PostPosted: Wed Jun 28, 2006 10:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yes, I am running it off batteries - the Casio runs off 5 "AA" batteries (7.5V total), so current draw is an important factor here - I'll check out the 7555. Is it a direct replacement for the 555, or does it have different pin-outs?

Thanks for the great advice Very Happy

Cheers, Graham
Back to top
View user's profile Send private message
dnny



Joined: Mar 12, 2005
Posts: 519
Location: Helsinki, Finland
Audio files: 8

PostPosted: Thu Jun 29, 2006 1:23 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Graham welcome to electro-music.com forum

have you tried 555 timer lite?. freeware that calculates the component values for desired timers using 555 and 556.

here is example whit 6volts (use only 4 AA batteries) and 20Hz (20times/second)
Posted Image, might have been reduced in size. Click Image to view fullscreen.
you can tweak the values until you get what you wanted.

should this topic be moved to our circuit bending sub-forum ?
opinions?

daniel

_________________
Association of experimental electronics
www.koelse.org
flickr: cable porn group
Back to top
View user's profile Send private message Send e-mail Visit poster's website Yahoo Messenger
Mikmo



Joined: Dec 01, 2005
Posts: 150
Location: Copenhagen - Denmark

PostPosted: Thu Jun 29, 2006 4:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Go to my website here:

http://www.mikmo.dk/cblfo.html

There's a 555 based LFO, compleate with VERO board and real PCB layout.

To get the timing you want just experiment with the potentiometer value and the timing capacitor.

_________________
Stay Cool
Mikael
http://www.mikmo.dk
Back to top
View user's profile Send private message Visit poster's website
gmeredith



Joined: Jun 28, 2006
Posts: 82
Location: Tasmania, Australia
Audio files: 1

PostPosted: Thu Jun 29, 2006 3:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks heaps, guys - looks like the thing I'm after! Thanks Daniel for the link and also the example 20hz - that will get me off to a good start. Thanks Mikmo for your circuit, I think I'll go with it!

Cheers and thanks, Graham
Back to top
View user's profile Send private message
Scott Stites
Janitor
Janitor


Joined: Dec 23, 2005
Posts: 4127
Location: Mount Hope, KS USA
Audio files: 96

PostPosted: Fri Jun 30, 2006 10:34 am    Post subject: Reply with quote  Mark this post and the followings unread

Don't forget to try a 7555 in there - I've become quite a believer in them. If you're using a battery, the 7555 will not suck it dry. They're also much, much better about not putting garbage on the supply lines. It's pin for pin to a regular 555.

Cheers,
Scott
Back to top
View user's profile Send private message
gmeredith



Joined: Jun 28, 2006
Posts: 82
Location: Tasmania, Australia
Audio files: 1

PostPosted: Sun Jul 02, 2006 5:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Scott,
Just finished building the circuit, I got a 7555 as you suggested, it's working really great!!

Just for those wanting a similar thing to me, if you look at the screenshot that Daniel kindly provided above, he showed an example 555 circuit with some values for R1, R2 and C1, to give an oscillation value of 20Hz.

I used the program to fiddle some more values, and came up with:

For a LFO range of 0.3 - 30Hz (an ideal range for your standard synth LFO) the values are:

R1 = 1k
VR2 = 500k
R2a = 4.7K
R3 = 4.7k
C1 = 4.7uF

See the attachment schematic - (a modified Mikmo circuit)

These values give a duty cycle of the LED of about 50% over the entire 0.3 - 30Hz range, which is also important for a synth LFO.


Cheers, Graham


555 LFO circuit.jpg
 Description:
 Filesize:  38.96 KB
 Viewed:  365 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

555 LFO circuit.jpg


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 [8 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