led project
Printed From: the12volt.com
Forum Name: Lights, Neon, LEDs, HIDs
Forum Discription: Under Car Lighting, Strobe Lights, Fog Lights, Headlights, HIDs, DRL, Tail Lights, Brake Lights, Dashboard Lights, WigWag, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=102516
Printed Date: May 15, 2024 at 6:43 PM
Topic: led project
Posted By: ShaunD912
Subject: led project
Date Posted: February 24, 2008 at 5:09 PM
I've built a small LED controller from a kit. This controller is made to control common anode RGB leds and it operates at 6 volts. Also, I have wired all of my leds to operate at 6 volts as well. I used ohm's law to caculate resistor values for each of the color leads, but then had to increase the values on some to make sure that all colors were even.
Here's my question. Previously, this controller has been used in my house and 6 volts was fine. But, now I want to move it to my Trailblazer. So, I do not want to rewire all of my LEDs as this would take a long time. Also, I know that the resistor values are fine at 6 volts. So, how do I calculate the resistor value to drop the 12v in my truck to 6 volts for this controller and the leds? All of the leds are parallel and have their own resistors.
I hope that this makes sense.
Replies:
Posted By: ShaunD912
Date Posted: February 24, 2008 at 5:19 PM
Would it look like this:
Here's what I'm thinking
(12v - 6v) / (30ma (R) + 30ma (G) + 30ma (B))
6/.09 = 67ohms
The part that's confusing me is that I assumed 30ma for each color when I originally calculated the resistor values for them, but all of the resistor values changed to match the color outputs. So, I'm not sure if I need to use 30ma or something else.
Posted By: Mad Scientists
Date Posted: February 25, 2008 at 11:28 AM
well, you could always measure actual current draw..<grin>. The only problem with dropping voltage with a resistor is current change.. if all the LEDs will always be on it's not a problem, but what if you turn one of the colors off?.. now you're seeing more voltage at the device (less drop across the resistor). Consider using a voltage regulator.. look at Radio Shack. Jim
Posted By: ShaunD912
Date Posted: February 25, 2008 at 11:40 AM
The more I look around, the less I think that my idea above is correct. It looks like I'm going to have to calculate the resistance for each of the colors individually. It seems complicated because for each color, I'll have one resistor for all leds plus a resistor on each led so it's a series and parallel connection. I'll have to draw it out.
Posted By: ShaunD912
Date Posted: March 11, 2008 at 9:51 PM
I got this to work and have installed leds in my dome lights and air vents. I'd like to share my work. Here's some links:
Color Change
Color Flash
Color Fade
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