traffic lights with white led lights instead of colored diy

let me start with that i know basically nothing, i thought it would be a go od project for my dad and i to do. Anyway, i have been searching online for schematics for a traffic light controller. i have found plenty,But none of them have it with white leds( i have a full size traffic light with the co lored lenses. so i only need white leds) also i have found that there are d ifferent schematics for white and colored leds. so i am looking for some he lp for a schematic and a parts list. if anyone can help in laymans terms th at would be greatly appreciated

Reply to
bigrdjimmy
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good project for my dad and i to do. Anyway, i have been searching online f or schematics for a traffic light controller. i have found plenty,But none of them have it with white leds( i have a full size traffic light with the colored lenses. so i only need white leds) also i have found that there are different schematics for white and colored leds. so i am looking for some help for a schematic and a parts list. if anyone can help in laymans terms that would be greatly appreciated

also i think i should be using about 5 leds per color, i hope it will be br ight enough

Reply to
bigrdjimmy

project for my dad and i to do. Anyway, i have been searching online for schematics for a traffic light controller. i have found plenty,But none of them have it with white leds( i have a full size traffic light with the colored lenses. so i only need white leds) also i have found that there are different schematics for white and colored leds. so i am looking for some help for a schematic and a parts list. if anyone can help in laymans terms that would be greatly appreciated

They use colored LEDs for better efficiency. Why use white LEDs, then waste the light in the filters?

Reply to
Michael A. Terrell

a good project for my dad and i to do. Anyway, i have been searching online for schematics for a traffic light controller. i have found plenty,But non e of them have it with white leds( i have a full size traffic light with th e colored lenses. so i only need white leds) also i have found that there a re different schematics for white and colored leds. so i am looking for som e help for a schematic and a parts list. if anyone can help in laymans term s that would be greatly appreciated

i fear the colors will get lost and not be as bright

Reply to
bigrdjimmy

good project for my dad and i to do. Anyway, i have been searching online for schematics for a traffic light controller. i have found plenty,But none of them have it with white leds( i have a full size traffic light with the colored lenses. so i only need white leds) also i have found that there are different schematics for white and colored leds. so i am looking for some help for a schematic and a parts list. if anyone can help in laymans terms that would be greatly appreciated

Colored LEDs will be brighter for the energy used because you won't be losing (as much) energy in the filters. The appropriate color LEDs really is the way to go. Greens, especially, can be very efficient (bright).

Reply to
krw

LED's don't lose colors.

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Tim Wescott 
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Reply to
Tim Wescott

be a good project for my dad and i to do. Anyway, i have been searching online for schematics for a traffic light controller. i have found plenty,But none of them have it with white leds( i have a full size traffic light with the colored lenses. so i only need white leds) also i have found that there are different schematics for white and colored leds. so i am looking for some help for a schematic and a parts list. if anyone can help in laymans terms that would be greatly appreciated

I would start with any schematic you found, that is, with colored LEDS. (I have found this:

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which may not be the one you found, but it won't matter)

To drive white LEDs you just have to tweak the limiting resistors (R4..R6 in the link). To be safe, begin with the biggest value in the schematic (probably the red one) and decrease the resistance until it looks bright enough (or the ammeter connected in series with one LED gives the value stated in the LED's datasheet).

Pere

Reply to
o pere o

You already have a shunt resistor built into the circuit. Just measure the voltage across it and divide by its resistance to find the LED current.

Reply to
krw

Absolutely true !

Reply to
o pere o

project for my dad and i to do. Anyway, i have been searching online for schematics for a traffic light controller. i have found plenty,But none of them have it with white leds( i have a full size traffic light with the colored lenses. so i only need white leds) also i have found that there are different schematics for white and colored leds. so i am looking for some help for a schematic and a parts list. if anyone can help in laymans terms that would be greatly appreciated

enough

Bright enough for what? Model train layout or real life traffic?

And what are the reliability requirements - leds may last "100,000 hours) gradually dimming.. but in a series connected string one failure may take out the string or shorten its life.

White leds are not a good choice since the phosphors used only fool our eyes into seeing white light - if you look at a spectrum of the light you see which bands are emphasized.

BTW a CD can be used as a diffraction grating (like a prism but different) to break out the bands so you can see what colors are there.

The reason for using colored LEDs is because the efficiency in their primary color is often higher than using white and losing all the colors you don't want through filters. Not to say that there aren't lots of aqua, green, pink, etc LEDs that use specialized phosphors to only emit one color (to our eyes anyway) that may be good choices.

Reply to
default

Nice starting place. :-) To the op: With the one at that url, you could move D4 to base of T1, & D6 to base of T3 to get longer green & red on times, and shorter yellow on time. As drawn, it gives equal on times for all three colors.

Ed

Reply to
ehsjr

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