Triggering a strobe with a phone flash in a underwater housing


I am trying to use my phone flash to trigger an underwater strobe and looking for your help. The flash easily activates the strobe when the fiber optic cable is placed in front of the flash outside the housing but the flash being so close to the lenses results in light being reflected back towards the camera resulting in hazy parts of the image.

I am looking to have the light be emitted near the hole below the flash as shown in the picture attached or in the following reddit post (Reddit - Dive into anything)

I have tried using a fiber optic cable placed 90 degrees to the LED with hot glue on each end but the light loss is too great and the strobe won’t trigger reliably.

I am looking towards using a light pipe to direct the light away from the lenses, probably a right angle low profile pipe as there is only about 3.5mm of clearance between the lens and the interior of the housing. Any ideas on how to achieve this? If a right angle light pipe exists that has a low enough profile, I could attache a fiber optic cable to it and then use a clear epoxy to diffuse the light towards the front of the housing.

I will attach the fiber optic cable from the strobe to the front of the housing with a mask and velcro so the external connection is not an issue.

Any ideas or recommended part numbers that may be useful in achieving this will be much appreciated.

Thanks in advance,


Add images

Hope this helps with your project.

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Hi handfida,

I don’t think a light pipe is likely to work in your application. The low profile is an issue, and most of them (especially low profile ones) are clear, and therefore likely to still have a fair amount of bleed-through and cause reflected light issues under your housing.

I was thinking that some sort of compressible rubber/silicone/etc. ring/gasket/grommet of the right thickness in an opaque color placed around the LED might be a better option. The purpose would be to prevent light bleed through below your clear protective cover but still allow the light to pass through to trigger your strobe. This would have the added benefit of not compromising your water-proof enclosure.

I was thinking something like this (forgive the crude drawing):

Thanks for the suggestions. I think you are right, all the light tubes are a few mm too high to fit. An issue is that on the outside of the housing the fiber optic cable is quite high and can be seen at the edge of the picture when in wide angle mode. I will play around with the positioning of the optic cable to see if I can move it slightly off center and avoid it being captured in the pictures or if on the very edge, will simply crop the images slightly.

Thanks Rhonda and David for your suggestions.