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I have a set of LED strips that have the following four wires:

  • Positive
  • Negative
    • Red Channel
    • Blue Channel
    • Green Chanel

Given these wires, I can produce the following colors without additional components:

  • Red
  • Blue
  • Green
  • Purple (Combine red and blue.)
  • Cyan (Combine green and blue.)
  • Yellow (Combine red and green.)
  • White (Combine red, green, and blue.)

However, the control module (now fried due to a crossed wire) has an option for amber/orange. The question is, how can I produce this color? I believe I may have to combine green and red to produce yellow, and add a resistor or similar to the green channel to reduce the current to that color thus displaying more red and possibly producing the desired color.


Additional Details

  • The lights are powered by a 12v source (car battery).

How can I use the above to create an amber/orange color from the lights?

If the answer is simply adding a resistor, what is the lowest resistor I should use in the 12v circuit?

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    \$\begingroup\$ You have the right idea: Since red + green = yellow, just increase the ratio of red to green. A resistor on green will do the trick. \$\endgroup\$
    – dpwilson
    Commented Oct 22, 2018 at 15:37
  • \$\begingroup\$ @dpwilson Even though red, green, and blue are negatives it'll still work? \$\endgroup\$
    – Taco
    Commented Oct 22, 2018 at 15:51
  • \$\begingroup\$ What do you mean by "red, green and blue are negatives"? Do you mean 'primary' colours? \$\endgroup\$
    – Transistor
    Commented Oct 22, 2018 at 16:04
  • \$\begingroup\$ @Transistor The strip has four wires; a single positive wire, and three negative wires that control the color. When I say this, I mean the positive wire goes to the positive on the power source, and the color wires go to the negative on the power source. I'm not the greatest with technical terms. \$\endgroup\$
    – Taco
    Commented Oct 22, 2018 at 16:07
  • \$\begingroup\$ Can you give us a current reading from one of the colours? Connect your multimeter on DC A range in series with one of the negatives and record the current. Switch the leads back to the V and COM when finished so that you don't accidentally take a voltage reading with the leads in the current sockets later. \$\endgroup\$
    – Transistor
    Commented Oct 22, 2018 at 17:06

1 Answer 1

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The resistor value you want will vary based on the amount of green you want, or the amber in general you want to see. It's safe enough that you can try a bunch of resistor to figure it out. Anything from 10 ohms to 500 ohms should be enough. You can put it on the negative side without issue.

Amber is, in rgb hex values 255, 191, 0. So green is roughly 75% of full brightness. Reducing it just a bit should help produce a nice orange color.

Once you found which value works best for you, measure the voltage across the resistor, and using ohms law, you can find the wattage needed for the resistor. P = (V^2 ) / R or V * I. The more current your led strip uses the higher wattage resistor you'll need.

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    \$\begingroup\$ Sorry about forgetting to mark as answered. I bought some 330 ohm resistors about a year ago and found them yesterday. Hopefully those will work because I’m not sure if I need to normalize the 12v to a 0-255 range for the calculation. \$\endgroup\$
    – Taco
    Commented Nov 24, 2018 at 14:15

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