Converting Fluorescents to LED ?

[binky]

what happens if you put 240V on a florrie tube? I suspect nothing due to insufficient voltage to excite the gas - haven't tried it to find out!

Incidentally I prefer to put sticker on the gear tray so it can be seen when changing tubes. I used to put them on the external surfaces, but dirt could obscure it, and sometimes diffusers get changed due to damage.

 

[Andy™]

on one end, like an LED is wired, its a short circuit

 

[binky]

so worse that could happen is MCB trips?

 

[Andy™]

many people replace tubes whilst power is on...

id expect its also possible for the tube to shatter

 

[binky]

ok florrie tube has an electrode both ends to excite gas, but that eelctrode is rated for what voltage? I'm trawling internet as I type, it seems to be capable of at least 216V as found so far.

 

[binky]

Fluorescent tubes and electroluminescent panels typically require 200 to 600 V for starting and running illumination, so a voltage of about 500 V is applied across the tube. This causes a small percentage of the mercury atoms to ionize (release electrons). These free electrons then accelerate towards the positive electrode and collide with the mercury atoms on the way. If an electron's energy is high enough, it can strip an electron off the target atom and create an additional free electron. This collection of free electrons and residual mercury ions classifies the argon-mercury combination as a plasma. If the impact electron is of lower energy, excitation of electrons in the orbitals around the mercury atom can occur. The mercury gives emission lines at 254 nm and 367 nm (in the ultraviolet region of the electromagnetic spectrum). 

OK, so the electrode must be able to withstand 200-600v, so 240v should not be an issue?  

 

[Andy™]

fluorescent tubes are designed for electric to flow from one end to the other in normal lit state. your LED has L&N on the same side, which fluorescent use as the heater for starting, which is pretty much a dead short

 

[Phoenix]

id expect its also possible for the tube to shatter

I'd suggest its not going to shatter the tube, but there will obviously be a bit of a pop, MCB will go, the new tube will be rendered useless (the pre-heat filament at the end acts as a sort of a fuse) and depending on the PFC at the fitting and how sharply it was twisted into place, the lamp holder may be damaged.

Tubes shattering (apart from being struck) tends to happen if the tube is already lit, and the choke suffers from a shorted turns situation, or is even shorted out entirely.... with the current flow through the ionised gas, the current is only limited by the choke, short part of it it and current goes up, power dissipated in the tube increases, pressure increases until the tube blows

 

[binky]

fluorescent tubes are designed for electric to flow from one end to the other in normal lit state. your LED has L&N on the same side, which fluorescent use as the heater for starting, which is pretty much a dead short

but the heater isn't a dead short and also designed to withstand the same voltages, even a trivial resistance will decrease PFC notably.