Why does an LED replacement for fluorescent tube start with a delay?

em. They wire directly to line current, no external ballast, but the tubes fit in the old tombstone connectors.

unlike the old fluorescents they replaced. BUT there is a long delay betw een flipping the switch and seeing them start. It's on the order of 1 - 2 seconds, I haven't tried measuring yet.

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 the y start immediately.

But, they do have an input range between 100 and like 270VAC. There is so me 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?

them. They wire directly to line current, no external ballast, but the tub es fit in the old tombstone connectors.

d, unlike the old fluorescents they replaced. BUT there is a long delay be tween flipping the switch and seeing them start. It's on the order of 1 -

y? It's not unique to mine, either, others have noticed similar results.

hey start immediately.

some sort of circuitry inside that keeps the current consistent as LEDs act a lot like zeners when it comes to over-volting them.

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

Mine are single end 4 foot tubes. They require a nonshunted tombstone, whi ch I was lucky enough to already have, but changing them out isn't hard. T he power wires go to only one end, and there was plenty of wire there to no t have to splice.

em. 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 o ld tombstone connectors?

unlike the old fluorescents they replaced. BUT there is a long delay betw een 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 ki nd of switch-off that operates to prevent a power surge from frying the LEDs. That protect ion circuit can be triggered by the power-on transient, and take a while to reset itsel f.

** 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

them. They wire directly to line current, no external ballast, but the tub es fit in the old tombstone connectors.

old tombstone

Yes. There were LED tubes available that worked on a ballast, and I consid ered 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 rep lacements were expensive. So I removed it and wired 120VAC directly to the tombstones.

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 connecte d 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 M icro makes a lot of controllers, and I have seen them in many LED TV suppli es. There is often a short delay depending on the control IC before the st ring is powered up.

The 8 footers I have power up almost immediately, but perhaps the controlle r 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 reac h 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

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.

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.

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.