Highly Liquid Forum facebook twitter google plus rss feed
  #1  
Old 05-31-2012, 10:20 PM
PushedButton PushedButton is offline
Member
 
Join Date: Jun 2010
Posts: 75
Default Volume Control using LDR's

I realise this isn't a midi question but I think someone here will find this simple.
What I want to do is have light sensors controlling the audio level of a set of portable speakers. They don't have to be powerful as they're going to be in the headrest of a wheelchair user.
The idea is to encourage the user to keep the light sensors covered for maximum volume. I think having one sensor in the middle of the tray would be a bad idea, it would be better to have a wider area of effect so the user was rewarded with more volume if both hands were anywhere along the front of his tray. In a roundabout way I'm saying I want to discourage him from raising either hand above his chin, there can be no means or restraint and nothing should be attached to him, which is why I considered LDRs. It would be inappropriate to explain in detail what this is all about but it's an idea I had to try to make someone's life a bit more bearable.
So to summarise, hands go down, volume goes up, one hand goes up, volume goes down. I'm a bit flaky at electronics but I'm sure someone here can translate this into something I can tell someone else to make cheers.
Reply With Quote
  #2  
Old 06-01-2012, 02:11 AM
Jim McDougall Jim McDougall is offline
Moderator
 
Join Date: Aug 2009
Posts: 395
Default

The easiest way to make this work will require tapping into the preamp level signal in the audio chain. YOu wold break the chain and insert a VCA voltage controlled amplifier ( several chips to choose from) Now to control volume you will need to provide a voltage signal to the control pin . This you want to vary with a photo resistor --- characteristics would be an increase in resistance with light exposure and a decrease in resistance with shadowing.

The alternative would be to use a photo cell but the out of that would have to have additional circuitry to invert the effect as the output increases with exposure to light and the output voltage is too low to be directly useful
Reply With Quote
  #3  
Old 06-02-2012, 12:19 AM
PushedButton PushedButton is offline
Member
 
Join Date: Jun 2010
Posts: 75
Default

Quote:
Originally Posted by Jim McDougall View Post
The easiest way to make this work will require tapping into the preamp level signal in the audio chain. YOu wold break the chain and insert a VCA voltage controlled amplifier ( several chips to choose from) Now to control volume you will need to provide a voltage signal to the control pin . This you want to vary with a photo resistor --- characteristics would be an increase in resistance with light exposure and a decrease in resistance with shadowing.

The alternative would be to use a photo cell but the out of that would have to have additional circuitry to invert the effect as the output increases with exposure to light and the output voltage is too low to be directly useful
that's awesome jim, I think I can get my head around that, thanks
Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 12:04 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.