FAQFAQ   GalleryGallery   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in   Forum RSS Feed   Hacked Gadgets Main Site 

Variable Resistors

 
Post new topic   Reply to topic    Hacked Gadgets Forum Index -> LED Projects
View previous topic :: View next topic  
Author Message
Chris Burdon
Newbie


Joined: 18 Mar 2007
Posts: 4

PostPosted: Sun Mar 18, 2007 12:48 am    Post subject: Variable Resistors Reply with quote

Right, wanting to do a multi-colour case interior with LED's and a fancy drive bay thing with variable resistors.

Those dials would controll the brightness of the red, green and blue portions of each 3 colour LED. this should obviously allow me to pick any colour i can see and project it all around the inside of the case.

Thats not the hard part though, obviously.

Does anyone know a formula i can use to work out what value of variable resistor i need to allow me to turn each colour from fully on (with the dial all the way in one direction) and fully off (all the way in the other direction) for each colour?

So... the variables would be
a) source voltage
b) diode forward current
c) diode forward voltage
d) number of LED's
to produce
x) resistance value of each of the 3 pots (which again, has to be enough to choke the power enough to make the corresponding fillaments not apear to be on)

got any clues anyone?
Back to top
View user's profile Send private message

Alan
Site Admin


Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB

PostPosted: Sun Mar 18, 2007 2:18 am    Post subject: Reply with quote

Hi Chris,

The main concern here would be that when the pot is turned to its lowest value (dead short) that the LED has the most current you would like it to see.

To calculate that fixed resistor value go here and plug in your numbers.
http://alan-parekh.com/led_resistor_calculator.html

Then you will have to pick a pot that will now limit the current, I would try some fixed values to see how dim (or off) your actual LED will look. For the pot I would shoot for limiting the current to something in the ballpark of 0.5mA or so.
Back to top
View user's profile Send private message Send e-mail
Chris Burdon
Newbie


Joined: 18 Mar 2007
Posts: 4

PostPosted: Mon Mar 19, 2007 1:06 am    Post subject: Reply with quote

cant believe i didnt think to use one fixed and one variable per colour and just aim to limit the current to .5mA *subs for B*

thanks a bunch Alan ^^
Back to top
View user's profile Send private message
Alan
Site Admin


Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB

PostPosted: Mon Mar 19, 2007 1:08 am    Post subject: Reply with quote

Chris Burdon wrote:
thanks a bunch Alan ^^


Anytime Cool

Snap some pictures so we can see how it looks when it's done.
Back to top
View user's profile Send private message Send e-mail
Display posts from previous:   
Post new topic   Reply to topic    Hacked Gadgets Forum Index -> LED Projects All times are GMT - 6 Hours
Page 1 of 1

 
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



Powered by phpBB © 2001, 2005 phpBB Group