Go Down

Topic: Strange RGB LED (Read 3435 times) previous topic - next topic

terdmcgurd

I am getting started with a Keyes LED RGB 140C05. It is an common cathode RGB LED with 331 ohm resistors.

I am using analogWrite to drive the pins, and I cannot reproduce colors. The colors I do reproduce are unexpected. Here is my code:

Code: [Select]
int redpin = 6;
int bluepin =5;
int greenpin =3;

void setup() {

  pinMode(redpin, OUTPUT);
  pinMode(bluepin, OUTPUT);
  pinMode(greenpin, OUTPUT);
 
  analogWrite(greenpin,255);
  analogWrite(redpin,255);
  analogWrite(bluepin,255);

}
void loop() {}



These are my results:
r      g      b         color         color w/o ground
255    0       0          off            off
0      255      0         white         pink
0      0      255         off            off

0      255      255         blue/green       blue
255      0      255         off            off
255      255      0         yellow          red

255    255      255         green      off
0      0      0         off            off


  • green has to be 'on' for others to work


  • red & blue only display up to value of green, but full on when no ground



I have tried to search for similar problems, and switch around the wires, but I find it difficult to describe the problem and the IC looks correctly labeled. Any tips? I feel like I must be overlooking something very simple.


PaulRB

#2
Aug 26, 2014, 08:23 am Last Edit: Aug 26, 2014, 09:05 am by PaulRB Reason: 1
Hi, sounds to me like its the result of a manufacturing error. I suspect it is in fact a common-anode led and the common has been labelled as green and green labelled as common. Red and blue labels are also swapped.

So... connect "green" to 5V and "common/ground" to the Arduino output. Swap your red and blue connections. An analogWrite value of 0 will turn a colour full on and 255 full off.

Paul

PS. The usual names of those colours: "blue/green" is called cyan and "pink" is magenta.

terdmcgurd

PaulRB,

That was indeed the problem. Kind of nuts. This is the result of having the wrong LED and having it hooked up wrong?  I am expecting to order a lot of 50-100 for a project. Is this type of thing common?

PS Thank you so much =] !! :)

Paul__B

#4
Aug 28, 2014, 12:49 pm Last Edit: Aug 28, 2014, 12:55 pm by Paul__B Reason: 1
Would the 4-pin LED having been soldered in to the PCB backward account for this?


bobcousins


That was indeed the problem. Kind of nuts. This is the result of having the wrong LED and having it hooked up wrong?  I am expecting to order a lot of 50-100 for a project. Is this type of thing common?


If you buy cheap stuff from China, yes :)

A colleague bought an iPhone car charger off ebay. Being a curious sort, he opened it up to see what regulation was used. There was none! 12V was wired direct from input to output.

Buying in volume seems to provide an opportunity to hide wrong spec/faulty parts, in some cases I've heard of 50% failure rates.
Please ask questions in the forum so everyone can benefit. PM me for paid work.

Go Up