Why does an LED replacement for fluorescent tube start with

[Tim R]

I had the ballast in an old two tube T12 fluorescent fixture go bad.

The local big box had direct replacement LED tubes on sale, so I tried them.. They wire directly to line current, no external ballast, but the tubes fit in the old tombstone connectors.

They work fine; they start at full brightness even when the room is cold, unlike the old fluorescents they replaced. BUT there is a long delay between flipping the switch and seeing them start. It's on the order of 1 - 2 seconds, I haven't tried measuring yet.

We've been discussing this on another forum. Why would there be a delay? It's not unique to mine, either, others have noticed similar results.

 

[John-Del]

On Monday, October 29, 2018 at 9:53:34 AM UTC-4, Tim R wrote:

I had the ballast in an old two tube T12 fluorescent fixture go bad.

The local big box had direct replacement LED tubes on sale, so I tried them. They wire directly to line current, no external ballast, but the tubes fit in the old tombstone connectors.

They work fine; they start at full brightness even when the room is cold, unlike the old fluorescents they replaced. BUT there is a long delay between flipping the switch and seeing them start. It's on the order of 1 - 2 seconds, I haven't tried measuring yet.

We've been discussing this on another forum. Why would there be a delay? It's not unique to mine, either, others have noticed similar results.

I picked up some 8' LED bulbs to retrofit the fixtures at my store, and they start immediately.

https://www.amazon.com/CNSUNWAY-LIGHTING-Dual-End-Replacement-Fluorescent/dp/B06VX4562H/ref=sr_1_3?ie=UTF8&qid=1540821784&sr=8-3&keywords=8%27+led+flourescent+tube+replacement

But, they do have an input range between 100 and like 270VAC. There is some sort of circuitry inside that keeps the current consistent as LEDs act a lot like zeners when it comes to over-volting them.

Do you have a link to the lamps you bought?

 

[Stephen Wolstenholme]

On Mon, 29 Oct 2018 06:53:31 -0700 (PDT), Tim R <timothy42b@aol.com>
wrote:

I had the ballast in an old two tube T12 fluorescent fixture go bad.

The local big box had direct replacement LED tubes on sale, so I tried them. They wire directly to line current, no external ballast, but the tubes fit in the old tombstone connectors.

They work fine; they start at full brightness even when the room is cold, unlike the old fluorescents they replaced. BUT there is a long delay between flipping the switch and seeing them start. It's on the order of 1 - 2 seconds, I haven't tried measuring yet.

We've been discussing this on another forum. Why would there be a delay? It's not unique to mine, either, others have noticed similar results.

All LEDs have some start delay. Even the original ones used for
indicators had a short delay. It's while the electrons fill the
electron holes where they should be.

Steve

--
http://www.npsnn.com

 

[Tim R]

On Monday, October 29, 2018 at 10:07:39 AM UTC-4, John-Del wrote:

On Monday, October 29, 2018 at 9:53:34 AM UTC-4, Tim R wrote:
I had the ballast in an old two tube T12 fluorescent fixture go bad.

The local big box had direct replacement LED tubes on sale, so I tried them. They wire directly to line current, no external ballast, but the tubes fit in the old tombstone connectors.

They work fine; they start at full brightness even when the room is cold, unlike the old fluorescents they replaced. BUT there is a long delay between flipping the switch and seeing them start. It's on the order of 1 - 2 seconds, I haven't tried measuring yet.

We've been discussing this on another forum. Why would there be a delay? It's not unique to mine, either, others have noticed similar results.

I picked up some 8' LED bulbs to retrofit the fixtures at my store, and they start immediately.

https://www.amazon.com/CNSUNWAY-LIGHTING-Dual-End-Replacement-Fluorescent/dp/B06VX4562H/ref=sr_1_3?ie=UTF8&qid=1540821784&sr=8-3&keywords=8%27+led+flourescent+tube+replacement

But, they do have an input range between 100 and like 270VAC. There is some sort of circuitry inside that keeps the current consistent as LEDs act a lot like zeners when it comes to over-volting them.

Do you have a link to the lamps you bought?

That's interesting. Yours are dual end powered (have to wire to both tombstones.)

Mine are single end 4 foot tubes. They require a nonshunted tombstone, which I was lucky enough to already have, but changing them out isn't hard. The power wires go to only one end, and there was plenty of wire there to not have to splice.

 

[whit3rd]

On Monday, October 29, 2018 at 6:53:34 AM UTC-7, Tim R wrote:

I had the ballast in an old two tube T12 fluorescent fixture go bad.

The local big box had direct replacement LED tubes on sale, so I tried them. They wire directly to line current, no external ballast, but the tubes fit in the old tombstone connectors.

Did you disconnect the ballast inside the fixture, that connects to those old tombstone
connectors?

> They work fine; they start at full brightness even when the room is cold, unlike the old fluorescents they replaced. BUT there is a long delay between flipping the switch and seeing them start. It's on the order of 1 - 2 seconds, I haven't tried measuring yet.

Either the ballast inside the fixture has a start-cycle, OR there's some kind of switch-off
that operates to prevent a power surge from frying the LEDs. That protection circuit
can be triggered by the power-on transient, and take a while to reset itself.

 

[Phil Allison]

Tim R wrote:

I had the ballast in an old two tube T12 fluorescent fixture go bad.

The local big box had direct replacement LED tubes on sale,
so I tried them. They wire directly to line current, no external
ballast, but the tubes fit in the old tombstone connectors.

They work fine; they start at full brightness even when the room
is cold, unlike the old fluorescents they replaced. BUT there
is a long delay between flipping the switch and seeing them start.
It's on the order of 1 - 2 seconds, I haven't tried measuring yet.

We've been discussing this on another forum.
Why would there be a delay?
It's not unique to mine, either, others have noticed similar results.

** Fluoro tubes are mostly used in commercial lighting and then in quite large numbers. A big inrush surge occurs when switching banks or a whole room full of tubes on - trips breakers, bad news.

The time delay built into many in LED version is there so the inverter circuitry can ramp up slowly, avoiding the usual brief but large current surge that accompanies the use of magnetic or most electronic ballasts.

In typical commercial applications, the tubes are switched on only *once* a day, so there is no issue as there might be in domestic use - all the LED bulbs I have seen come instantly on.

Some even fade out after switch off, just like an incandescent.


..... Phil

 

[Tim R]

On Tuesday, October 30, 2018 at 6:25:47 PM UTC-4, whit3rd wrote:

On Monday, October 29, 2018 at 6:53:34 AM UTC-7, Tim R wrote:
I had the ballast in an old two tube T12 fluorescent fixture go bad.

The local big box had direct replacement LED tubes on sale, so I tried them. They wire directly to line current, no external ballast, but the tubes fit in the old tombstone connectors.

Did you disconnect the ballast inside the fixture, that connects to those old tombstone
connectors?

Yes. There were LED tubes available that worked on a ballast, and I considered doing that because it would allow a retreat to fluorescent if I didn't like them, or if they became unavailable. But my ballast was bad, and replacements were expensive. So I removed it and wired 120VAC directly to the tombstones.

 

[Terry Schwartz]

Oh those troublesome holes. Takes forever to fill 'em. Insatiable.

LED's are much faster than incandescents. Look at most any vehicle that has LED's in the side mirrors and incandescents in the rear turns. The timing is visibly different and painfully obvious. At least one vehicle maker has recognized this and compensated for it in the driver timing, even PWMing the LEDs during turn on to emulate the familiar incandescent "warm up".

The inherent flicker in LED tail lights (and other LED lighting) bothers the crap out of me. I know not everyone sees it, but apparently my eyesight is a bit more responsive than some. I see the flicker in neon signs and various LED backlights as well.

The PWM rate is designed to be faster than normal visual threshold of detection, but below the audio threshold of annoyance... that is, over a hundred HZ or so, but out of the sweet spot of human hearing, a few hundred HZ to a few KHz. It seems counter-intuitive that the visual threshold is lower than audio, but in this case, it is.

The PWM rate could easily be set above the hearing range, but that has potential implications for causing EMI certification problems.

We installed LED lights in our bathroom fixtures -- and one of the wifes' hair appliances modulates the LED bulbs badly. I'm not sure if I should blame the bulbs or the curling iron in this case.

Terry

All LEDs have some start delay. Even the original ones used for
indicators had a short delay. It's while the electrons fill the
electron holes where they should be.

Steve

--
http://www.npsnn.com

 

[Look165]

Anyway, for LED you don't need aballast.

It is a resonant circuit designed for HPOT generation.

Kill it off and connct the LED directly to the mains '(w/o diodes).

You will have immediate lightning ; it is the ballast which introduces a
delay.


Tim R a Êcrit :

I had the ballast in an old two tube T12 fluorescent fixture go bad.

The local big box had direct replacement LED tubes on sale, so I tried them. They wire directly to line current, no external ballast, but the tubes fit in the old tombstone connectors.

They work fine; they start at full brightness even when the room is cold, unlike the old fluorescents they replaced. BUT there is a long delay between flipping the switch and seeing them start. It's on the order of 1 - 2 seconds, I haven't tried measuring yet.

We've been discussing this on another forum. Why would there be a delay? It's not unique to mine, either, others have noticed similar results.

 

[John-Del]

On Wednesday, October 31, 2018 at 12:05:24 PM UTC-4, Look165 wrote:

Anyway, for LED you don't need aballast.

It is a resonant circuit designed for HPOT generation.

Kill it off and connct the LED directly to the mains '(w/o diodes).

You will have immediate lightning ; it is the ballast which introduces a
delay.

How many times does OP have to say he wired around the ballast and connected directly to the AC source?? He also said he switched to LEDs because his ballast was dead.

Internally, they don't connect the LED string to the AC. So first there's a rectifier, then there's an LED current control circuit of some kind. The time the LED string will be powered up will depend on the controller. O2 Micro makes a lot of controllers, and I have seen them in many LED TV supplies. There is often a short delay depending on the control IC before the string is powered up.

The 8 footers I have power up almost immediately, but perhaps the controller IC in OP's tubes delay the output until the input filter is fully charged by design. Since LEDs don't put out any significant light until they reach close to their run voltage, maybe his controller just ramps up the string slower than the one in my 8 foot tubes.

The fact that all his examples do the same tells me it's just the way it's designed and not a failure.

And once again, he DISCONNECTED the ballast and wired them directly.

 

[pfjw@aol.com]

Please note the interpolations:

On Wednesday, October 31, 2018 at 11:33:32 AM UTC-4, Terry Schwartz wrote:

Oh those troublesome holes. Takes forever to fill 'em. Insatiable.

LED's are much faster than incandescents. Look at most any vehicle that has LED's in the side mirrors and incandescents in the rear turns. The timing is visibly different and painfully obvious. At least one vehicle maker has recognized this and compensated for it in the driver timing, even PWMing the LEDs during turn on to emulate the familiar incandescent "warm up".

There are LED lamps and there are LED lamps. "Responsible" makers such as RAB & Cree (and a few others) feed smoothed DC to their lamps, greatly reducing and/or eliminating flicker. Some few of the retro-lamp makers (those that require removal of the ballast and so forth) do the same. But far fewer than with the complete fixture.

> The inherent flicker in LED tail lights (and other LED lighting) bothers the crap out of me. I know not everyone sees it, but apparently my eyesight is a bit more responsive than some. I see the flicker in neon signs and various LED backlights as well.

Agreed on this. But, as you note, some makers take care to handle this in their vehicles. Our Ford C-Max side-mirror led signals are synched well for example. Vehicle systems can be a mixed bag, depending on how well filtered the Alternator might be.

The PWM rate is designed to be faster than normal visual threshold of detection, but below the audio threshold of annoyance... that is, over a hundred HZ or so, but out of the sweet spot of human hearing, a few hundred HZ to a few KHz. It seems counter-intuitive that the visual threshold is lower than audio, but in this case, it is.

The PWM rate could easily be set above the hearing range, but that has potential implications for causing EMI certification problems.

We installed LED lights in our bathroom fixtures -- and one of the wifes' hair appliances modulates the LED bulbs badly. I'm not sure if I should blame the bulbs or the curling iron in this case.

See the first instance. We tried (cheap, as in FREE) some utility-supplied LED lamps in the kitchen at our summer house - and instantly lost FM reception anywhere within a 30' sphere of these lamps. We switched over to SMT LED fixtures (no separate lamps) and all became well.

I will soon find out a lot more about LED retrofits. We are about to install about $1,500,000 in conversion fixtures and retro-lamps in the buildings I manage based on a fairly chunky Utility rebate. These are medical offices, outpatient clinical spaces and heavy-duty research facilities - gene splicers and all that. So, if there is any tendency for mutual interference, I will know soon. The installer says not. Famous last words, or not.

It is a very mixed bag, and one size does not fit all.

Terry

All LEDs have some start delay. Even the original ones used for
indicators had a short delay. It's while the electrons fill the
electron holes where they should be.

Steve

--
http://www.npsnn.com

Peter Wieck
Melrose Park, PA

 

On Wed, 31 Oct 2018 09:36:29 -0700 (PDT), John-Del <ohger1s@gmail.com>
wrote:

On Wednesday, October 31, 2018 at 12:05:24 PM UTC-4, Look165 wrote:
Anyway, for LED you don't need aballast.

It is a resonant circuit designed for HPOT generation.

Kill it off and connct the LED directly to the mains '(w/o diodes).

You will have immediate lightning ; it is the ballast which introduces a
delay.


How many times does OP have to say he wired around the ballast and connected directly to the AC source?? He also said he switched to LEDs because his ballast was dead.

Internally, they don't connect the LED string to the AC. So first there's a rectifier, then there's an LED current control circuit of some kind. The time the LED string will be powered up will depend on the controller. O2 Micro makes a lot of controllers, and I have seen them in many LED TV supplies. There is often a short delay depending on the control IC before the string is powered up.

The 8 footers I have power up almost immediately, but perhaps the controller IC in OP's tubes delay the output until the input filter is fully charged by design. Since LEDs don't put out any significant light until they reach close to their run voltage, maybe his controller just ramps up the string slower than the one in my 8 foot tubes.

The fact that all his examples do the same tells me it's just the way it's designed and not a failure.

And once again, he DISCONNECTED the ballast and wired them directly.

I just replaced some incandescent bulbs with LED bulbs and they have a
delay like the OP describes. The new LED bulbs are the dimmable type.
I wondered if the delay is coming from a cap being charged through a
resistor. They also have an off delay similar to an incandescent. Not
exactly the same but they do dim until almost completey off and then
abruptly turn off all the way.
Eric

 

[bilou]

Tim R avait soumis l'idée :

I had the ballast in an old two tube T12 fluorescent fixture go bad.

The local big box had direct replacement LED tubes on sale, so I tried them.
They wire directly to line current, no external ballast, but the tubes fit in
the old tombstone connectors.

They work fine; they start at full brightness even when the room is cold,
unlike the old fluorescents they replaced. BUT there is a long delay between
flipping the switch and seeing them start. It's on the order of 1 - 2
seconds, I haven't tried measuring yet.

We've been discussing this on another forum. Why would there be a delay?
It's not unique to mine, either, others have noticed similar results.

To start the switching control IC needs a 12V supply.
The only low cost way to get it is by slowly charging a capacitor from
rectified mains through a rather big dropping resistor.
After start a special transformer winding takes care of the 12V.
If the LED lamp can be used on both 120/240 VAC start must be much
slower with 120V.
Here in France I never really noticed the problem.
On the other hand,normally off lamps, sometimes blink slowly in the
dark
because of capacitive coupling of the wiring around the switch.

 

[Look165]

the cap is useless.

Just make sure you have a rectifyer bridge instead than a simple diode
as rectifyer.

think od half sine and double sine feed.



Tim R a Êcrit :

I had the ballast in an old two tube T12 fluorescent fixture go bad.

The local big box had direct replacement LED tubes on sale, so I tried them. They wire directly to line current, no external ballast, but the tubes fit in the old tombstone connectors.

They work fine; they start at full brightness even when the room is cold, unlike the old fluorescents they replaced. BUT there is a long delay between flipping the switch and seeing them start. It's on the order of 1 - 2 seconds, I haven't tried measuring yet.

We've been discussing this on another forum. Why would there be a delay? It's not unique to mine, either, others have noticed similar results.

 

[Tim R]

On Saturday, November 3, 2018 at 2:32:14 PM UTC-4, bilou wrote:

On the other hand,normally off lamps, sometimes blink slowly in the
dark
because of capacitive coupling of the wiring around the switch.

I have not noticed this, but there is approximately 15 feet (5 meters) of mains wire between the switch on the wall and the light.

When I lived in Germany many of the light switches were momentaries, and just changed state of the breaker in the panel. Here in the US I've never seen that done. The light switch on the wall directly controls the power to the light.