Question about LED Lights

[ClassicalBGP]

So, I ordered a LED T5 light tube/bulb thinking it would plug into the current fixture. I think it's a normal 12v light fixture for a flouresenct bulb. It came in, I popped the cover and it fit and worked. However, then I realized there was wire attached to the back of the bulb. I pulled it and then looked at the instructions. The instructions say to bypass the ballast. Knowing nothing and trying to learn here. I really don't want to cut wires I don't have to and it worked. Why the bypassing and what harm could it cause not to?

[belizesailor]

Ive converted most of my 12v flourecents to LED, but by bypassing the ballast. Since driving LED is not what the ballast is designed to do, it never dawned on me not to bypass it. But, Im not sure what harm it could do to LED.

Where did you buy your LEDs?

Hope someome will chime in and answer that question.

[ClassicalBGP]

Came from Batteries Plus. Im hoping someone can shed some light on the subject. I'm not so much worried about the $20 led, but starting a fire or using more power than the normal bulb.

[svHyLyte]

The ballast in a florescent light fixture is designed to provide a momentary "blast" of very high voltage to spark an arc between the electrodes on either end of the light tube. The arc excites the gas within the tube which emits light. Once the arc is established, the voltage is dialed back. Using an LED fitted tube replacement with the ballast will rapidly "cook" the LED's.

As a practical matter, with the high quality low power LED replacement tubes available today (ours are from Marine Beam), there is no good reason the retain the ballast On can simply snip the wires and remove it, entirely, or leave it in place and connect the disconnected power wires to either end of the bulb mount. Considering their cost, but prospective longevity, they are an economical replacement but not if you're going to cook them up with the unnecessary ballast.

FWIW...

[belizesailor]

Thanks HyLyte, seems obvious now that you describe it.

[ClassicalBGP]

Originally Posted by belizesailor

Thanks HyLyte, seems obvious now that you describe it.

Second that. Thank you and once put that way, it's a no brainier.

[UNCIVILIZED]

Note that there are some lighting fixtures where an LED bulb will fit, as well as light up, but provide unsatisfactory, & unsafe lighting. Such as in some navigation lights for example, unless they've been designed around LED bulbs from the start. So it's worth check'em before making such a purchase.

[malyea]

Good info...how do I "check" the existing fixture? Thanks

[ClassicalBGP]

I just cut the ballast out and re-wired the bulb to the switch. Works and the fixture is there simply holding the bulb and switch. Anyone for see an issue?

[belizesailor]

Originally Posted by malyea

Good info...how do I "check" the existing fixture? Thanks

What do you mean by "check"?

If it is flourecent flourecent then it has an electronic module (ballast).

[belizesailor]

Originally Posted by ClassicalBGP

I just cut the ballast out and re-wired the bulb to the switch. Works and the fixture is there simply holding the bulb and switch. Anyone for see an issue?

No issue as long as LED bulb has built in voltage regulation.

Ive done the same thing. Remove ballast and wire to switch (you dont actually need to remove the ballast you can just by pass it).

[J Clark H356]

The ballast is not needed for the T5 LED bulb and should be disconnected.

[StuM]

Warning!

Lots of bad information in previous posts in this thread.

Originally Posted by svHyLyte

The ballast in a florescent light fixture is designed to provide a momentary "blast" of very high voltage to spark an arc between the electrodes on either end of the light tube. The arc excites the gas within the tube which emits light.

That's the "Starter", not the ballast and that's not quite how it works.

Once the arc is established, the voltage is dialed back. Using an LED fitted tube replacement with the ballast will rapidly "cook" the LED's.

The ballast limits the current, not the voltage. The ballast provides resistance. Without it, the fluorescent tube will draw more and more current until everything burns out.

...Considering their cost, but prospective longevity, they are an economical replacement but not if you're going to cook them up with the unnecessary ballast.
FWIW...

The ballast won't "cook" an LED replacement, it just puts extra resistance in the circuit.

Check out: How does a fluorescent starter work? | HowStuffWorks for how the starter works.

And more on what the ballast does:
https://en.wikipedia.org/wiki/Electrical_ballast

[belizesailor]

Another related link on how flourecent bulbs work on DC:

http://www.electricalbasicprojects.c...-on-dc-supply/

Not much different, just need to switch the DC polarity regularly to avoid damage to bulb.

So, to the original question. Appears to me the voltage, amps, and polarity coming out of the circuitry for a DC fixture will all vary. If the circuitry in the LED fixture can handle this then it will work.

I expect a low quality, not self regulated, LED would either not work at all or have a very short life...maybe milliseconds during the start spike.

A good quality self regulated LED may work (depending on its circuitry capabilities), but I suspect the additional and frequent "work" the circuitry would have to do would shorten its life.

Anyone know specifically how the circuitry of a self regulated LED would be affected?

[belizesailor]

Marine Beam sells an LED bulb which uses the existing connections on a flourecent fixture, making the conversion easier, but the "ballast" must still be bypassed (thats Marine Beams use of the term not mine...I assume they really mean all the flourecent related circuitry, but on the fixtures Ive converted its all on one circuit board. So refering to the board as "ballast" is convenient, but technically incorrect).

For the OP, this link also contains videos on how to convert an existing fixture to LED.

http://store.marinebeam.com/12-f8t5-...ures-fl-t5-66/