older traffic light bulbs were special heavy duty lamps run at a slightly lower voltage. have seen the bulbs, they were big on mechanical strength.
traffic lights have tough lives, vibration from passing trucks, impacts, extreme weather, etc etc.
a fellow who fixed them said voltage didnt just snap off and on, it ramped up and was never completely off, which backed up a lamp assembly i saw one nite, it had opened somehow and the off color positions were glowing very slightly. would f never been seen with the colored glass in place
note the newer LED lamps, when they fail area go out, rather than the entire lamp
not long ago I saw a hanging traffic lamp broken from its mount, spinning in the wind. big storm going on
I called 911 immediately if that fell thru a windshield someone could get hurt bad. a hour or two later i passed the intersection on the way home the lamp assembly was gone.
the tech must of hated me, he had to do that in a severe storm
Traffic lights with incandescents use "traffic signal lamps". Most of those are rated for 8,000 hours and there are 130V versions.
I have heard a bit about blinking signs and "chaser light" signs having a "keep warm" current to reduce thermal shock, or that the filaments don't cool enough to run into thermal shock problems. I have my doubts about keep-filament-warm means since cold starts are generally not as damaging as people think, and any such current would make "off" lamps glow in signs that have most the lamps burned out - and I don't see that happening. Traffic signals don't have any "low current" to keep the filament warm - or else drop-in LED replacements would glow somewhat when they are "off".
I have seen inside the controller boxes for traffic signals in Philadelphia, back when they used incandescents for all colors. They use mechanical switching - voltage does not ramp up.
If the light is the only thing on that side of the float, and if it is turned off, then nothing will function. However while someone may only know of one item on the circuit, usually there is more than one. Same deal on the other side. If the two sides are balanced then both sides get normal voltage and current, but that seldom happens. Often voltage changes as loads vary so while it may appear normal some times, at others it may be running at twice the rated voltage or zero.
This is a real thing, not a something someone thought up in their head. Just because you did not think of an additional load on that circuit in addition to the lamp does not mean there is not one. That is the whole reason for codes, to protect all of us from our own ignorance.
I doubt that they could "ramp" the current very easily back in the pre-solid state electronics days. But maybe they just used resistors across the switch contacts on the one you saw? That would keep the filament warmer during the "off" periods.
And, the electricity "wasted" that way was MUCH cheaper in those good 'ol days.
I'm the OP and found the problem the other day, turns out the bulbs were not burned out after all. The screw in socket was very tight so the bulb was not able to seat completely down to make electrical contact - properly do to rust from the salty air. The property is located close to the Pacific Ocean. A little Vaseline on the thread and pulling the hot center tap out a little bit had solved the problem. Regarding the salty air, I also needed to replace the exterior door bell button once every three or so years as the contact fail to conduct due to corrosion.
I know what you mean, I dont mine fluorescent lighting for general illumination but for any type of task lighting I want incandescent. There is an exception to this. At work we have 3 phase power in the building and when the lights in the room are split among the three phases it doesnt bother me.
I have seen them with a ballast resistor in series with them. The ones I remember used a cam to activate switches. The cam was driven by a ratchet device amd soleniod. It might take 3 or 4 ratchets before anything changes.
"Jimmie D" wrote in news:47f3c3f3$0$6474$ snipped-for-privacy@roadrunner.com:
MythBusters did a short segment regarding light bulbs.
Lights On or Off
Myth: You save on energy bills by leaving lights on. Some people believe that the energy to turn on lights exceeds savings of turning lights off.
They talked to Mark Reisfelt, manager of the Independent Electric Supply where they purchased their light bulbs. He felt that it was best to turn the lights off.
To test the myth, they needed to measure energy usage during startup, maintenance (steady state), and shutdown.
For steady state energy consumption, they turned on several different types of bulbs for 60 minutes and measured their consumption using a Kill A Watt: * Incandescent 90 Wh * Compact Fluorescent (CFL): 10 Wh * Halogen: 70 Wh * Metal halide 60 Wh * LED: 1 Wh * Fluorescent: 10 Wh
For startup energy consumption, Grant hooked up an inductive current loop to a computer and measured the amount of energy used when the turned on the bulbs. With an inductive current loop, you run a wire through the center, which induces a current in the loop. This current is then measured by a digital sampling oscilloscope.
Based on the amount of energy consumed turning on the bulb, they were able calculated how long the bulb would have to be turned off in order to make it worth the energy savings, i.e. "It's best to turn off the bulb if you are leaving the room for":
In other words, its almost always best to turn the bulb off. Even the 23 seconds for the fluorescent lights isn't very long, and the rest of the times are pretty much blinks of an eye. Bulb Longevity
They tested one final element of this myth: frequently turning lights on and off decreases their life span, thus leading to greater costs. Grant setup a timer and relay to turn the bulbs on and off repeatedly every 2 minutes. After six weeks, only the LED bulb was still working. Based on this test, they extrapolated that it would take five years of ordinary usage to cause the bulbs to burn out.
busted * Side-note: 105-year bulb
Grant and Kari visited the Livermore/Pleasanton Fire Department to view their light bulb that has been burning for 105 years. It has a carbon filament that is much thicker than modern bulbs and also burns much cooler/darker. You can check on the light using the bulb's webcam.
Philadelphia converted nearly all of their red traffic signals to LED sometime in the late 1990's, at a time when red LED traffic signals had GaAlAsP LEDs instead of InGaAlN ones. (The older chemistry glowed a deeper shade of red, and was less efficient - red traffic signals of that type consumed something like 30 watts, and the newer LED chemistry got that down to something like 11-15 watts.)
A few percent, maybe several percent of Philadelphia's red traffic signals have some LEDs out, but they are still largely working after something like a decade.
Many of Upper Darby's red and green traffic signals were converted to LED a few years ago. A couple of the green ones have a few LEDs out.
I seem to think that the LED ones are greatly outlasting incandescent ones.
The 23.3 seconds is more than the actual truth for fluorescents. Fluorescent fixtures that draw increased current during starting also have their power factor reduced during starting, and the above setup appears to me to measure only current consumption.
Fluorescents and HID lamps (such as metal halide) do suffer wear from starting. Halogen and HID lamps can also age badly if they spend a lot of "on time" incompletely warmed up.
2 weeks being on half the time is 504 hours. Many incandescents are only rated to have average life expectancy of 750 hours.
I have seen the webcam picture. Based on this and web searching, I suspect teh filament is indeed running at an unusually low temperature, and with much less energy efficiency than that of modern incandescents.
You can get 230V lightbulbs. Some electrical/lighting supply places, as well as online outfits such as bulbs.com, sell them. At 120V, they should easily last a century. A 200W 230V lightbulb at 120V consumes about 75 watts, and produces about 2/3 the light output of better 40 watt 120V incandescents. A "century bulb" is easy to achieve, but no bargain.
It could be that what I am seeing isnt a direct failure of the LED but there are 12 traffic signals from my house to work and 4 of them have sections that are out or flcikering and these lights are only about a year old. Of course this could represent the failure of only few LEDS in a few thousand as I imagine the LEDS are probably arrange in series /paralell clusters where if oneLED failed several others would also be taken out.
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