Can any dive light be turned on/off underwater?

[gcbryan]

You can turn led's on and off as often as you want to above and below water. Halogens can be turned on and off but it's harder on the bulbs when you turn them on (just like any bulbed light) but it's only the HID's that shouldn't be turned back on immediately after turning them off.

Any dive light should be capable of being turned on or off underwater.

 

[Jim Lapenta]

I have an LED cannister and just as a matter of practice turn it on before the dive and off when I surface. Not because it is supposed to be but as other have said the switch on any light is a potential failure point. I had a uk switch break off under my thumb and flood the light. I now only use twist on and off. My backups I don't turn on until needed but once on they stay on until I'm out of the water.

 

[spectrum]

It depends on the dive and the light.

If it's a night dive then I need the light so once on, it stays on to avoid the failure potential from switch breakage or lamp stress.

If it's a day dive and I use a light to peer into a dark space then it gets turned off.

These are not HID lamps.

Pete

 

[DennisW]

I don't own an HID light, but the posters here who do obviously know the issues with heat and those types of lights. My dive light is normally only on when I want to see something specific. Most of the divers that dive at night have enough light to dim the sun, so when I dive at night with a group, I save my batteries. Besides, it is interesting to be in the dark sometimes. The bioluminescence is much more noticable when the lights are off.

 

[Web Monkey]

I keep hearing how dive lights should be turned on above water and left on for the duration. is this true? can any be cycled on/off underwater safely? I know my Tec 40 is not supposed to be cycled cut I just got a UK SL4 and was wondering about it.

HID bulbs have a limited number of startup cycles, so if you turn it off, it might not come back on, although once it's on it should stay on as long as the battery lasts.

LED lights can be cycled on and off as often as you want.

Personally, I don't care how bright, white or "focused" any HID light is. Their fragility makes them unsuitable for underwater use. I'd much rather have a light that can be dropped on the boat floor with no damage and will run all night on a single set of batteries, than one that has a little nicer light, but needs to be treated like it's made from fine crystal.

Terry

 

[TSandM]

I've seen a video of (I think it was) Barry Miller pounding nails with the light head of a 21W HID with the Brightstar bulb. I don't think they have to be treated like they are fine crystal. I've certainly dropped mine a time or two!

 

[miketsp]

You can turn led's on and off as often as you want to above and below water. Halogens can be turned on and off but it's harder on the bulbs when you turn them on (just like any bulbed light) but it's only the HID's that shouldn't be turned back on immediately after turning them off.

Any dive light should be capable of being turned on or off underwater.

Just a couple of comments.

If you turn a halogen bulb on then you should let it heat up to its operating temperature before turning it off again. This comes from the halogen cycle:
"How does a halogen lamp work?
It works through the halogen cycle. As tungsten evaporates from the filament, it combines with halogen gas and becomes tungsten halide. This tungsten halide state is maintained at temperatures between 250°C and 1400°C. The temperature of the bulb is kept above 250°C in order to maintain this state and prevent the tungsten from sticking to the bulb wall and darkening it. When the tungsten halide nears the filament, the heat of the filament separates the tungsten from the halogen gas, redepositing the tungsten on the filament. The freed halogen gas then repeats the same process again thus the halogen cycle."

Every time you turn off a halogen bulb that has not yet reached its operating temperature you deposit some of the tungsten on the bulb wall.

As for being able to turn on or off any dive light UW,then yes in principle that's correct. However it's important to bear in mind that at depth, unless you have magnetic or sealed switches with a boot, you may have a lot of sand or grit from the suspension being forced into the o-rings and the external pressure is trying to push this into the light. So when you operate the twist-on-off type or even normal toggles at depth you may be chewing up the o-ring.

 

[lucca brassi]

For halogen it exist very simple solution -Soft-start circuit even with overvoltage. Bulb will last much more longer ! It can be simple only with resistors and relay or NE555 or with some special circuit or with uC.
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HID can be switched on/off with AC based lamps ( inside circuit is so called H- bridge for push-pull function (like power amplifiers for speakers ) which have alsoso caled '' hot restrike''. This ballasts are normaly for automotive industry but some lamp makers have ballast made on that concept (like Hartenberger for example) . AC lamps are normally designed for ower 35W ; under this wattage belongs to DC based lamps.

Normal , most common HID lamps in diving area have DC powered lamps ( W-A , Brightstar), which dont like very much turning on/off because of nature of ignition that uses electrodes much more.

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LED has no such problems.

 

[DiveNav]

I never had any problem turning back ON my lights while underwater.

As someone else said, it is actually quite interesting to turn off your lights during a night dive and watch the Bioluminescence surrounding you .... sometime I feel like an Angel with my own halo

Of course I always carry with me a couple of back up lights .... just in case,

Alberto (aka eDiver)

 

[gcbryan]

I like turning my light off underwater at night as well but if I'm using a HID dive light I do it near the end of the dive and try not to have to turn it on again. With a LED it's not an issue. Is anyone even still using halogen?