Rich, do you have any diodes in these LED circuits?
It seems to me that this might simply be the bipolar LED not liking the DCC signal on the one color?
LED’s are after all, DC devices. The DCC signal is not really DC.
The thing that concerns me about this is voltage drop?
Sheldon
No, I do not have any diodes in the signal wiring, but I wonder if diodes are the solution to the bi-polar LED wiring. I wish that I understood more about such wiring.
When you say that you are concerned about voltage drop, are you saying that powering the LEDs off the rails may pull too much power from locomotive performance?
Rich
isn’t this a good thing?
should the signal be clear if the turnout is routed straight, and indicate a lessed indication if switched to the diverging route?
and shouldn’t the signal toward the turnout on the diverging route be either stop or approach (yellow)?
Not a good thing. What is happening is that instead of turning from red to green, it is trying to show both colors and it turns out an orangey color which is why I referred to it as amber. I need a way to block the green LED when the red LED is activated. The search light signal is a bi-polar red/green LED, no yellow.
Rich
Yes
OK, I found the solution to the bi-polar LED issue.
By placing a diode in line with the Green LED wire, I can prevent a current backflow that was turning the red/green LED to an orange blended color.
Now, my only concern is bleeding off too much DCC power by wiring the signals to the DCC-powered rails. I do have a RRampMeter hooked up to the layout, so later today I will check the effect of voltage drop. One or two signal hookups should not matter, but I have a considerable number of signals to wire up, so voltage drop may be a serious issue. Any thoughts?
I just tested with my RRampMeter. Each signal draws 0.01 amp. That would mean that it would take 100 signals, more than double what I need, to consume 1 amp of DCC power. Wouldn’t that be acceptable?
Rich
i think so
Rich
10ma on LEDs is a bit too bright for me, I would add some resistance to drop it to 5ma. That would drop your total current from 1 amp to a ½ amp.
Mel
My Model Railroad
http://melvineperry.blogspot.com/
Bakersfield, California
I’m beginning to realize
Hi Rich,
I agree with Mel. Increasing the value of the resitors will not only save you some power, but you may also find that the brightness of the LEDs is toned down to the point where they don’t burn your eyes if you look straight at them. I have seen some signal systems where the LEDs were so bright they were almost blinding.
Dave
I run my three color LEDs at;
Red 2ma
Yellow 11ma
Green 4ma
At those current levels they look pretty close to me in brightness. Easily seen at full room brightness and not to bright for my moonlight scenes.
Mel
My Model Railroad
http://melvineperry.blogspot.com/
Bakersfield, California
I’m beginning to realize that aging is not for wimps.
Hi Mel,
I’m working on tri-colour signals for a friend. I’ve only worked with tri-colour LEDs once before and those were for classification lights so having them bright wasn’t too much of an issue. I’m curious to know what value resistors you are using.
Thanks,
Dave
Dave
My 82 yr old brain isn’t doing much today. I had to go to my MEGA and look at the resistors.
I’m driving my LEDs (SMTL4-RGY) from the Arduino MEGA 5 volt power supply.
The red is 1KΩ = 2ma @ 5 volts
The green is 560Ω = 4 ma @ 5 volts
The yellow is 180Ω =11ma @ 5 volts
Voltage makes a huge difference in the current draw of a LED, at 10 volts double the size of the resistors and at 15 volt triple the values.
I really like the SMTL4-RGY LEDs they work better than GREAT.
You have better vision than I do, at better than 30 years older than me. No way can I do those super fine wires on SMD devices. And unfortunately nothing can fix that, I’m for the most part only seeing out of one eye, so it’s not just the sharpness, my depth perception is off.
Are those the RGY LEDs from RR-CirKits? The ones he sells have a perfect aqua green for railroad signals - the typical green LED is WAY off. You might not notice it until you see what one of the nice ones looks likes.
–Randy
Randy
The LEDs I went with are SMTL4-RGY from Bivar.
https://www.bivar.com/Files/Datasheets/SMTL4-RGY.pdf
I bought mine from Mouser, best price. 25 LEDs for $31 delivered. They are available from most large electronic stores.
While attempting to solder the first one I went with a surgical clamp to hold it, shortly after clam
Hi Mel,
Thanks for the resistor values.
Do you have a picture of the green indication? The LEDs that I am using for the club’s signals are about $4.00/100. The Canadian price for 100 of the LEDs that you are suggesting is $155.00 incl. tax and shipping. I’m not happy with the green tone on the cheap LEDs but I’m reluctant to spend that much money unless the green is hugely superior.
Dave
All of this talk about about milliamps prompts me to ask, how do you determine the amount of milliamps on an LED. I have seen various reports stating LED current draws to be 20 to 30 ma without a resistor attached. Is there a way to measure exact milliamps for a specific LED?
Rich
with a light meter.
20ma is typically the max. But over the years, LED optical intensity has increased. The value for different color LED and manufactures may be different.
Thanks, greg. It does seem that 20 ma is the standard, so I will move forward on that assumption.
Rich
Dave
I’m not very good taking pictures but I tried on the SMTL4-RGY
I had used three wire bi-color LEDs for my first signaling system about 20 years ago and they worked out great. When I was in the designing and planning portion of my current project I wanted to go with common Anode. I also used the brass tube of the signals as common, I never liked the idea of having an “electrically hot” pole that close to the tacks.
I tried several batches of the newer three wire bi-color LEDs in both common anode and cathode all had unusable yellow color and pitiful at best green. I went into search mode for months and finally ask on the Forum. Randy suggested a