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Wiring a tri colored LED

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  • Member since
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  • From: Southern Quebec, Canada
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Wiring a tri colored LED
Posted by Guy Papillon on Tuesday, January 7, 2020 4:46 PM

I just received a searchlight with two lights. Each light is a tri colored LED.  Each LED has three wires: one green, one red, one yellow and one black.  For now, I want to control the lights manually. How can I do that with a DPDT Switch for each light?

The searchlight was bought on eBay and came without any instruction.

Guy

Modeling CNR in the 50's

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Posted by BigDaddy on Tuesday, January 7, 2020 5:01 PM

It's not obvious to me how a DPDT switch could control 3 separate functions.  This is how tri colored Leds work.

Henry

COB Potomac & Northern

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Posted by nealknows on Tuesday, January 7, 2020 5:45 PM

I would use a 3 position rotary switch to control each position. I'm not savvy in posting electrical diagrams but I'm sure someone here can add to my comment. 

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Posted by Mark R. on Tuesday, January 7, 2020 9:02 PM

You say each LED has THREE wires .... red / yellow / green / black. That would be four wires. I'm assuming it is similar to the BLMA signals that use chip LEDs and there are three separate LEDs in the head. The black would be common and the other colors would match the appropriate color.

To attain three different colors, you would need either a multi-position switch or a pair of SPDT switches.

If using the two SPDT switches, feed the power into the first switch. Up position would feed the red light, down would send the power to the second switch which would feed either the green or yellow.

Mark.

¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ

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Posted by BigDaddy on Tuesday, January 7, 2020 9:30 PM

I was going to chew on Mark for accusing Guy of not being able to count to 4.  The video link I posted shows only 3 leads, but on closer inspection of the WeHonest signal, there are 2 lights, 6 wires connected to resisitors and 2 black wires hiding underneath.  Then I re-read the OP post and 4 is 4

If there are 4 wires, WeHonest has a plan and a manual switch for that.

 

 

Henry

COB Potomac & Northern

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Posted by Guy Papillon on Wednesday, January 8, 2020 7:24 AM

Thank you everyone. The searchlight I bought is similar to the WeHonest Signal. I will buy the manual switch recommended for that kind of signal. I was not aware that there were three LEDs in each head as the searchlight was advertised as being made of three colored LEDs.

Finally, I agree with everyone that 4 is FOUR.  My bad. ☹️

Guy

Modeling CNR in the 50's

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Posted by rrinker on Wednesday, January 8, 2020 7:38 AM

 Well, in a way it is - it is made up of 3 (quantity) color LEDs, not a 3 color (type) LED. Which is better, - the best you ever get out of the 3 wire bicolor red/green LEDs is a kind of sickly orangish color. With the advent id ultra tiny LEDs, now they can put 3 microsocopic individual LEDs on one small board and you get an actual dedicated yellow LED for the yellow color, instead of trying to mix it by varying a red and green together. Finally searchlight signals can have the same colors as a 3 light signal head.

                                --Randy

 


Modeling the Reading Railroad in the 1950's

 

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Posted by BigDaddy on Wednesday, January 8, 2020 11:05 AM

You should look for Mel's comments on 3 color led's.  He uses different resistors for different colors

Henry

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Posted by RR_Mel on Wednesday, January 8, 2020 11:41 AM

The LEDs I use are SMTL4-RGY, three LEDs in one 3mm package with four solder terminals.
 
 
I drive the three color LED with an Arduino MEGA.
 
The three colors are not linear in brightness to current requiring a difference in resistance for each color for equal brightness.
 
The resistors for driving the SMTL4-RGY from 5 volts are as follows: 

2ma for Red - 1000Ω

12.5ma for Yellow/Amber - 180Ω

4ma for Green - 560Ω

To my eye the three colors are well balanced for equal brightness at the above currents.
 
 
 
 
Mel
 
 
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 
 

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