Author Topic: Blink-unhappiness!  (Read 2659 times)
arcblue
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Blink-unhappiness! « on: March 09, 2011, 01:29:34 AM » Author: arcblue
I found another NOS preheat F30/40 ballast and installed it in an F30 fixture that previously was rapid-start. To my dismay, it likes to start instantly as soon as the switch is turned on, or sometimes it will light dimly, go out and come right back on at full brightness. I tried all my spare starters (all new GE's) and it makes no difference which one I use.

The lamp is an older Philips (not an Alto) that says "Rapid Start". Do I need to find an older lamp that is designed for preheat ballasts, or change to another brand of starter, or am I just doomed to an instant-starting preheat fixture? My mains voltage is right about 120v, sometimes slightly under, so I don't think that's the problem. Ballast is an Advance brand, probably manufactured within the last 5 years.
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Medved
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Re: Blink-unhappiness! « Reply #1 on: March 09, 2011, 02:20:30 AM » Author: Medved
The blinking at startup on the preheat circuit is (from lighting equipment development point of view) perceived as highly undesirable behavior, to be suppressed as much as possible.
An ideal is seen in about a second preheating (so "nothing happen" at switch turn ON) and then direct light up, no flashes at all. So if everything work perfectly, the preheat would start exactly that way (you would likely consider boring... ;-) ).

In your case it look, then the ballast provide too high OCV, so it frequently start the lamp instantly before the starter heat up and close (immediate light up), the grounded metal reflector close to the lamp (required for the RS) is aiding this instant starting. This was not considered as a problem either...

So try to put the lamp more far away from the reflector (disconnecting the ground i would not recommend, as it would be unsafe).
Then the starting would correspond to the "preheat ideal" (as it sometimes happen according to your description)
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DieselNut
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Re: Blink-unhappiness! « Reply #2 on: March 09, 2011, 08:22:08 AM » Author: DieselNut
Also, try reversing the starter 180 degrees in its socket. They perform differently sometimes with the current flowing through them in the opposite direction. Some starters even say "for optimum performance, try reversing starter in its socket".
Never thought about what Medved said about the grounded reflector but that makes sense. The ungrounded or plastic cased (like some under cabinet lights) do seem to be the most  "blink happy".
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arcblue
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Re: Blink-unhappiness! « Reply #3 on: March 12, 2011, 08:05:38 PM » Author: arcblue
Thanks for the info. I never thought of the reflector acting as a starting aid for a preheat fixture, but it makes sense. Old metal preheat lights had longer sockets so the lamp mounted further away from the reflector.

I suppose the occasional instant-start won't hurt the lamps...I would only be concerned if they were vintage lamps, since many electronic ballasts now instant start the lamps everytime anyway.

You're right...the blinking is undesirable, but I enjoy it...and I usually only switch a particular fixture on once a day anyway. The GE starters that I have generally start the lamp about perfectly, then...just a short preheat and then on, maybe one blink at most. What I really hate is starters that won't work in the dark :)
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Medved
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Re: Blink-unhappiness! « Reply #4 on: March 14, 2011, 08:16:05 AM » Author: Medved
@Reflector & instant starting:
On preheat fixtures is no (electrical) limitation on the reflector position, so it's placement was driven mainly by optical efficiency (minimum light loss by reflecting light back onto the tube) versus overall size and manufacturability trade-off. And this yield to ~half of tube diameter distance between the reflector and the tube.
On the other hand RS ballast need to have the grounded conductor close to the lamp in order to work properly and the cheapest way to ensure this was placing the reflector so, it just touches the lamp, sacrificing the optical efficiency a bit.
And as the fixture was originally RS, it's design is made more according to RS requirements...

And with metal fixture i made one observation: F8T5 operated on series choke ballast at 230V close to grounded metal reflector start instantly without the starter (with the starter connected it start normally as preheat - apparently the starter limit the peak voltage). And the tube was for sure already worn out, as removing the starter was apparently "working solution" to "fix" the flashy light in an rented apartment (it worked like that for more then half year, till i moved out)...
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nogden
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Re: Blink-unhappiness! « Reply #5 on: March 22, 2011, 07:18:51 PM » Author: nogden
My F30 fixture with a rapid start T12 lamp is not blink-happy at all either. It never instant starts, but it always starts on the first click of the starter. I actually like how well it starts, although it has no entertainment factor! It does hum quite loud when the starter is closed though.
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TL8W
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Re: Blink-unhappiness! « Reply #6 on: May 18, 2011, 02:26:14 PM » Author: TL8W
Sometimes repeated blinks before starting occurs at lower temperatures - below 10C (50F) for example as the arc in the tube takes a higher voltage than normal at low temperatures. I have measured the voltage of 12" lamps (nominal 56v) and seen values of over 90v for about half a minute when the lamp is started cold - the same lamp blinks several times before settling.

In the UK low temps can even cause normal lamps to BEGIN cycling when exposed - often seen in illuminated "fascia" shop signs using 6ft 70w T8s. It was something I picked up on during our exceptionally cold (by UK standards!) winter of 2010/11.
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Zelandeth
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Re: Blink-unhappiness! « Reply #7 on: May 19, 2011, 01:22:31 PM » Author: Zelandeth
I've found the F100 I have here almost always starts with the first blink (since the new starter was installed anyway...would sit flicking, pinging and blinking madly for about 30 seconds before!).

I've also got a Tamlite F8T5 fixture here which *always* instant-starts the tube (with a satisfying "thonk" sound from the ballast), completely irrespective of what starter is in it save for electronic ones.

Another F20 two foot fixture I have baffles me, in that it always instant-starts F18T8 lamps, but takes forever to an F20T12 to start...Given that the striking voltage of the F20 is lower, I would have thought that was the easier of the two to start.  All of the above are just normal switchstart ballasts.
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Re: Blink-unhappiness! « Reply #8 on: May 20, 2011, 01:22:26 AM » Author: icefoglights
Out in the shop, I have an F40 American Fluorescent under cabinet fixture over the workbench.  It originally had an electronic instant start ballast, but I converted it to magnetic preheat, using a 1981 Advance ballast.  The lamp is a late-90s GE F40KB.  I've found when it's turned on, the lamp will glow dim, similar to when a rapid start is first switched on.  It goes out when the starter closes, and lights to full brightness when the starter opens, usually on the first try.
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Kev
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Re: Blink-unhappiness! « Reply #9 on: May 20, 2011, 02:34:54 AM » Author: Kev
Temperature definatly does effect blink happyness! I find that T12 are better in the cold than T8. As lee just said about our cold winter in the shed at work i installed various lights. most being switch start T8. I noticed that one of the 6' kept cycling for a good 5 minutes before it started up and was stable where as the 8 foot just started in -5 the same as it would in +25!
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icefoglights
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Re: Blink-unhappiness! « Reply #10 on: May 20, 2011, 02:45:35 AM » Author: icefoglights
That was one of the reasons I converted that light to magnetic preheat was reliable starting in temps below -18°C (0°F)
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Luminaire
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Re: Blink-unhappiness! « Reply #11 on: May 21, 2011, 01:55:50 PM » Author: Luminaire
Magnetic preheat, more or less provides the same current to the filament as connecting the choke directly across line, and it often fails to fire on first pulse when the starter opens.

It is actually one of the most damaging way of starting lamps, because the filament is often overheated which causes evaporation of emissive coatings on cathodes and the flashing during start-up causes sputtering. 

By far the most lamp friendly way of starting is electronic programmed start, which if designed correctly, provides filament Rh/Rc ratio of about 4, then apply instant-start like voltage with the filaments hot, reducing both over-heat induced evaporation and sputtering. 

The lamp acts like a resistor with HF operation, because the cycling is fast enough to keep the lamp going through zero crossing, which may actually increase lifetime.

There's a special 18" F15T8 meant for use on electronic ballast only, by GE, which is rated at 24,000 hours, just like their F32T8.  A standard switch start F15T8 is only rated at 7500 hrs 
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Re: Blink-unhappiness! « Reply #12 on: May 21, 2011, 04:00:08 PM » Author: nogden
I do agree that electronic program start is a good way to start lamps. However, I've noticed some program start ballasts don't last as long as the tubes! Eventually we will start using fixtures where the tubes are built-in and the ballast is easily replaceable.
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Luminaire
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Re: Blink-unhappiness! « Reply #13 on: May 21, 2011, 11:21:49 PM » Author: Luminaire
I do agree that electronic program start is a good way to start lamps. However, I've noticed some program start ballasts don't last as long as the tubes! Eventually we will start using fixtures where the tubes are built-in and the ballast is easily replaceable.

There are some high bay fixtures with pop-off lid on the top for easy ballast replacement.  You could do what programmed start does using traditional methods using relay logics, RC timer and such but it would be very costly
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Medved
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Re: Blink-unhappiness! « Reply #14 on: May 22, 2011, 02:16:54 AM » Author: Medved
It is actually one of the most damaging way of starting lamps, because the filament is often overheated which causes evaporation of emissive coatings on cathodes and the flashing during start-up causes sputtering. 

Sputtering is not caused by the flashing on hot electrodes (as this is nothing else then normal discharge), but by the discharge with electrodes not yet warmed up (so when the first flash after very short heating already start the lamp - mainly when using "high wattage" starter on "low wattage" bulbs). The "overheat" is way not as severe, as the thermionic discharge (white glow around electrodes) limit both the filament voltage (by providing shunt path for the current) and temperature (emitted electron carry lot of energy, what cool the filament down)
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