Large Scale Central

LED wiring for Bi-Color LEDs

Electronics
#21

David Maynard said:

Daktah John, well there is a difference in additive colours and subtractive colours when we talk about primary colours. That confuses some people. With light, red, green and blue make white. With dyes/paints/pigments cyan, magenta and yellow make black.

So yous scused.

Sorry David,

But those pigments make mud, not black. As we know black is the absence of color. Back in college, I dabbled.

You are correct that there are two color wheels; one for light and the other for pigments.

#22

John, if the pigments are true and pure you can get real close to black, but as you said, its not pure black. I have seen dark blue, dark brown (mud) and dark purple on the copiers I work on, when they print out what we call “process black”. That is, black made with the 3 colours, Magenta, Cyan and Yellow.

#23

Artist Acrylics stay muddy.

Ink is another realm to me.

John

#24

Back on Topic… IT WORKS !! I went to the internet and ordered more then I needed, As this electronic stuff is my weakest link in life skills. I am setting out to improve my skills, So I bought a DC Power supply, a breadboard ( its much smaller then the pictures lead you to believe) with itty bitty little jumpers, Mouser supplied me with a bunch of CL2’s and a bag full of diodes, China shipped a gazillion resistors in about every conceivable size ( 7.5 ohm to a whooping 4,700,000 ohm ) and 100 bi-color red green LEDs for $3.99 including shipping.

Followed my own schematic and it worked. Well not the first time. BTW a 2VDC LED will light with 15 volts applied… It just doesn’t light for very long, well actually about 1/10,000 of a second, but it did light. Lesson learned… Double check what little hole you put that itty bitty jumper wire in. Poof, its dead… Lesson Two, CL2’s work only with power going the right way, DUH… I fried two complete LEDs and the Green side of another one.

Note switch position: The air solenoid kicked in, and the two lights lit opposite to each other.

And throw the switch and whaaa Aha…

Now this is my very first ever bread board rig up… I know its pretty simple, but I got it to work right.

Now I think that I will need to build a circuit board to mount all the diodes on and the CL2s to keep them out of trouble in the control panel.

#25

And is the red brighter? It looks to be. (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-cool.gif)

#26

Yup… Just like you said that it would be, But not as bad as I thought. The LEDs are frosted with a wider viewing angle, and actually its the red ones that I wanted to be most noted, as that indicated that that line is blocked. This is a cell phone pic, so no real control of the settings.

OK my newbe ignorance, If I was wanting to “Balance” the intensity I would have to restrict the current to the red side by adding a resistor, thereby making it not so bright, Or, increase the current to the Green side, making it burn brighter, but greatly reducing it’s lifespan. OR both? If I put a resistor in series to the red side to decrease the current and it matches the green side, If my voltage changes, then all bets are off as to the “Balance”, or with the CL2 controlling the input, would the resistor in series on the red leg of the LED just help control the red side, and have no effect on the green side?

#27

To reduce the current with the CL2, what you need to do is bypass current around the led, therefore you need to add a resistor in parallel to the LED to effectively reduce the current to the LED.

#28

Dan, Again my learning curve needs a diagram. I’m not sure that I will change from where I am, which is the second schematic. But I want to learn and understand, so that I can if I change my mind. A simple sketch on a napkin will work.

And I think that there are several other non-electronic types trying to following along too.

Thanks for the learning help.

#29

Dave Taylor said:

Yup… Just like you said that it would be, But not as bad as I thought. The LEDs are frosted with a wider viewing angle, and actually its the red ones that I wanted to be most noted, as that indicated that that line is blocked. This is a cell phone pic, so no real control of the settings.

OK my newbe ignorance, If I was wanting to “Balance” the intensity I would have to restrict the current to the red side by adding a resistor, thereby making it not so bright, Or, increase the current to the Green side, making it burn brighter, but greatly reducing it’s lifespan. OR both? If I put a resistor in series to the red side to decrease the current and it matches the green side, If my voltage changes, then all bets are off as to the “Balance”, or with the CL2 controlling the input, would the resistor in series on the red leg of the LED just help control the red side, and have no effect on the green side?

I don’t think that you would be able to simply add an additional resistor on the red side because the current limiter would try to compensate for this and allow more current to flow when the red is on. But you can try it in series and/or parallel. Worst that can happen is you fry more parts.

If you end up using two “devices,” they may as well just be the resistors, which as I noted are cheaper and you don’t need to think about polarity (as you found out).

You know how to do the calculations and have the pieces to try various combinations. Just shoot for 20 - 22 milliamps on the green and 20-30% less on the red and see how that looks to your eye. A 10% current overage will have little impact on the LEDs life.

Also, recognize that the “go to” resistor for train engine headlights is 1,000 ohms @ 1/4 watt. If the engine runs up to 24 volts, that’s 22 milliamps. Also, at 24 volts, that’s ~1/2 watt. If the train runs at 12 volts, that’s 10 milliamps, but you can still see the headlight in daylight.

#30

To have current bypass the LED, you would need to connect one leg of a resistor to one leg of the LED, and the other leg of the resistor to the other leg of the LED. If you have 2 volts on the LED, and 20 miliamps, and you want to drop it 10%, then you would want 2 miliamps flowing through the resistor. 2 volts divided by 2 miliampes is 1000 ohms. Of course when you start shunting some current past the LED, the voltage would most likely change a bit. So I would start with 1000 ohms in parallel with the LED, like I said in the beginning of my post. If the red LED gets too dim, then use a higher value resistor, if you want it dimmer, then use a lower value.

#31

If I had a cheap “regulated” 12v supply that metered at 13.9 I would throw it away. If later the same supply now read 14.5 volts, I would not throw it away, but smash it flat with a sledge hammer so no one else could use it.

Seriously, after all the $$ you spent on the air solenoids, you have a cheap supply (and it is malfunctioning?) ??

Greg

#32

Greg, I see your point, but then again if its working why “fix” it? Besides, even with a regulator, doesn’t the output go up a bit without a load on it? Yes, 14.5 sounds excessive.

#33

OK guys… I’ve had my doubts about the power supply from the start. I went up to Mouser, searched for 12Vdc 3amp power supplies, and I’m not sure what I need, Switched or regulated and what is the fundamental differences? Would a “super” wall wort work?

#34

Switched power supplies use less power, and run cooler then a regulated power supply. If the super wall wart can supply enough power it might work, but personally I would think that it would be kind of cumbersome, and it would probably run rather hot.

#35

OK guys, I think that I found a new power supply. Again I really don’t know what for sure that I’m really needing. Here is a link to the Mouser site, Do ya’all think that this will do the job. It is rated at 6Amps, they also have ones at a bunch of other Amp ratings. I think that I’ll draw about 2.5, so my reasoning is that the 6amp one gives me plenty of spare, and won’t be working so hard. Your thoughts are greatly appreicated.

http://www.mouser.com/ProductDetail/Mean-Well/LRS-75-12

#36

Yea, you don’t want to push a power supply to its max all of the time. I would think that would do the job for you. You would want to mount it somewhere where someone could not accidentally touch the input voltage screw terminals, but it looked to me like you had a control panel to mount it behind, where it will be safe.