I have made myself an RGB LED nametag and want to dim its RGB LED, but with normal dimming, the dimming doesn´t seem to be linear.
To control it, I use a default LED strip remote control like this one:
The top left buttons are for dimming. In my code, I have a variable called dimmingFactor which can have values between 1 and 10. So how can I correctly dim the RGB LED linearly without changing the given color?
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Read this
@jim-p I already tried it with this table, but it doesnt seem to work any better. But I'm also unsjre if i have implemented it correctly with my dimmingFactor with values between 1 and 10. Could you give me a piece of example code for dimming with the table?
Do you mean interger values only 1,2,3,4,5,6,7,8,9,10.
Post your current sketch to see how we can help.
@paulpaulson @kolaha Heres the code. The intensity always has a value between 1 and 10, where 1 is the lowest and 10 is the highest. And with this code, the LED even turns off if the intensity is too low.
const uint8_t gammaCorrectionTable[] = {
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2,
2, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5,
5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 9, 9, 9, 10,
10, 10, 11, 11, 11, 12, 12, 13, 13, 13, 14, 14, 15, 15, 16, 16,
17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, 23, 24, 24, 25,
25, 26, 27, 27, 28, 29, 29, 30, 31, 32, 32, 33, 34, 35, 35, 36,
37, 38, 39, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 50,
51, 52, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 66, 67, 68,
69, 70, 72, 73, 74, 75, 77, 78, 79, 81, 82, 83, 85, 86, 87, 89,
90, 92, 93, 95, 96, 98, 99,101,102,104,105,107,109,110,112,114,
115,117,119,120,122,124,126,127,129,131,133,135,137,138,140,142,
144,146,148,150,152,154,156,158,160,162,164,167,169,171,173,175,
177,180,182,184,186,189,191,193,196,198,200,203,205,208,210,213,
215,218,220,223,225,228,231,233,236,239,241,244,247,249,252,255 };
void RGBLED::setColor(byte r, byte g, byte b) {
if(!isOn()) {
return;
}
int dimFactor = 11 - intensity;
int dimmedRed = gammaCorrectionTable[r / dimFactor];
int dimmedGreen = gammaCorrectionTable[g / dimFactor];
int dimmedBlue = gammaCorrectionTable[b / dimFactor];
analogWrite(rPin, dimmedRed);
analogWrite(gPin, dimmedGreen);
analogWrite(bPin, dimmedBlue);
currentRValue = r;
currentGValue = g;
currentBValue = b;
}
yes
Try this:
index = 30+(intensity-1)*25)
PWM_val = gammaCorrectionTable[index]
analogWrite(xPin,PWM_val)
@jim-p Seems to work, thank you 
But why does it work?
@jim-p and actually, this only works for a single led. But i have a rgb led and somehow have to consider the r, g and b values provided by the arguments of setColor
Check the (datasheet) power usage of LEDs (red, blue and green). Higher power consumption will show a greater effect with decreasing PWM duty cycle. Maybe use an LDR directly "on top" of each LED, in a black box, to measure the brightness (compare brightness?). The results should help with the different dimming-step levels.
Do the same thing 3 times, once for each color.
why does it work?
You have 10 intensity levels and the array size is 256.
256/10=25.6, so I incremented the index by 25
If I start at 30 rather than 25, the last index will be 255
@jim-p but how do i take the original colour value and the intensity in mind? Because that are two values. is it e.g. for red only r/(11-intensity)?
@jim-p and is there a reason you add 30 instead of 5 and subtract 1 from the intensity?
They probably are very close to linear. It's our human eyes that are not linear!
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