Can any dive light be turned on/off underwater?

[Aigtbootbp]

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.

 

[Gombessa]

Generally, leaving it on is a good course of action; the switch, whether it's a button, twist-contact, switch, magnetic reed etc. is a potential point of failure, and bulbs tend to break more as they're cycled than when they're just "on." So the recommendation that lights not be turned on and off in the water is there to minimize the chances that you'll end up underwater, in the dark, without a light.

All that being said, all underwater dive lights that I've ever seen are more than capable of being turned on and off while underwater. I'd be a bit dubious of any dive light that wasn't designed to handle being cycled while submerged.

 

[a22shady]

Depending on the light. As for HID Canister Lights they are supposed to be only turned on under water due to heating of the componets. You can flip it on right before getting in but probably just smart to do it once your in and ready for it. I have other lights and no other people who have there lights on when they need it and off when done under water both Canister lights and hand helds.

 

[ScubaSteve]

I'd be a bit dubious of any dive light that wasn't designed to handle being cycled while submerged.

For me, this is what it is all about. I would be very leary of any light that came with rules restricting a diver's ability to turn it on/off as required. I have heard of lights that should not be burned for long on the surface due to temperatures however I have never seen or heard of restriction for use underwater.

 

[ptyx]

I was told that HIDs don't like being turned on and off - and liked some cooling off after shutoff before being turned on again. According to my instructor then, HIDs should be turned on at the beginning of the dive (once underwater) and left on for the duration as much as possible to limit the risks of failure.

As far as I remember, that was specific to HIDs. The advice is consistent with the safeguards media projectors have. Is it yet another urban legend?

 

[ScubaSteve]

I was told that HIDs don't like being turned on and off - and liked some cooling off after shutoff before being turned on again. According to my instructor then, HIDs should be turned on at the beginning of the dive (once underwater) and left on for the duration as much as possible to limit the risks of failure.

As far as I remember, that was specific to HIDs. The advice is consistent with the safeguards media projectors have. Is it yet another urban legend?

Here you are talking about cycling correct? Or were you told that turning a light on halfway through a dive or off half way through a dive will destroy the light?

I am asking this about the HID because I am not familiar with them.

 

[Tanked]

I was told that HIDs don't like being turned on and off - and liked some cooling off after shutoff before being turned on again. According to my instructor then, HIDs should be turned on at the beginning of the dive (once underwater) and left on for the duration as much as possible to limit the risks of failure.

As far as I remember, that was specific to HIDs. ?

I have the UK light cannon and turn it on underwater, and leave it on till I'm on the way up.
I've turned it off, and then back on right away, and it takes some time for it to get bright. So now I just leave it on during the dive

 

[Gombessa]

I was told that HIDs don't like being turned on and off - and liked some cooling off after shutoff before being turned on again. According to my instructor then, HIDs should be turned on at the beginning of the dive (once underwater) and left on for the duration as much as possible to limit the risks of failure.

As far as I remember, that was specific to HIDs. The advice is consistent with the safeguards media projectors have. Is it yet another urban legend?

The HID lamps (bulbs) are fairly fragile, similar to the halogen bulbs but much more expensive to replace. More powerful underwater HIDs such as 21w generate a lot of heat, and aren't designed to dissipate it very well above water, so yes these lights are only designed to be run under water for extended periods of time (longer than 30 seconds or so).

Also, striking an HID (turning it on) does put stress on the lamp, so you want to limit the number of times you turn it on and off if possible (and you certainly shouldn't hot-strike it). For me, this doesn't mean you can't turn it on and off if you need to, but you shouldn't flick it repeatedly like a strobe. If my light goes out underwater, I'll turn it off and on to see if it comes back, but if it doesn't, I turn if off and change to a backup light.

 

[Bubbletrubble]

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.

Umm. I own a few Princeton Tec 40 (compact halogen) lights and a couple of the UK SL4s (xenon). They serve as my backup lights. They can be turned on/off under water just like a lot of other halogen, xenon, LED lights.

The lights that you don't want to flip off and then back on quickly are HID lights, e.g., UK Light Canon, certain canister lights. It's my understanding that a hot HID light cannot be restarted because the voltage required to establish the "arc" would be too high for the electronics to provide. That's why you have to wait for the HID light to cool off first before turning it on again. (Don't quote me on this since I'm not a light expert by any stretch of the imagination.)

In summary, feel free to flip your Tec 40 and UK SL4 lights off and on. Don't go too crazy, though, because I guess it's possible to wear the bulb out prematurely if you do it too much. Hope this info helps...

 

[ptyx]

Here you are talking about cycling correct? Or were you told that turning a light on halfway through a dive or off half way through a dive will destroy the light?

I am asking this about the HID because I am not familiar with them.

I was told that turning a HID on puts a lot of stress on the bulb compared to regular burn. Stress is bad over time because it leads to premature bulb death, but the deciding factor was that the extra stress means turning the bulb on is the moment the bulb has the highest probability to die (statistically speaking). The reasoning was that it was perfectly ok to turn a HID off at mid dive, but turning it back on would have a higher risk of failure than if it had been left on. Cycling was a no-no.

Given the price of a bulb and the annoyance of your main light going out in the middle of the dive, that was worth the 'don't do it'.

My engineering bull**** detector wasn't screaming at the time, and isn't today - but I'm not a light specialist. Maybe someone will have an authoritative answer on the subject? (Tobin?)