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Not as tall in real life
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Are there any bright sparks on board who could give me some pointers on how to make a moisture detection system ?

Basically, I have a alloy camera housing and would like to build a circuit that could detect a slight leak.  I was thinking of something small, lithium button cell powered, with a red LED that I could fit just inside the window.

I guess a simple couple of wires at the bottom of the housing that would make a circuit if bridged by water would work but I was kind of hoping for something a bit more clever, maybe resistance based.

Daz
 

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The water is going to have a very high resistance so you will need to detect this and use it to trigger a light. There is probably a simple beginners kit from Maplin which will do that. You could get a cheap book on op-amp circuits and have a play.

If you are interested I can describe basically how the op-amps work.
 

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Even easier, get some self indicating silica gel, it will a) remove small amounts of moisture and b) tell you it has done so.

The reality of a small leak is that it is either not big enough to matter on a dive, or will kill the camera, what use is a sounder at 30M, it is already too late.

An opinion, but I must admit I have considered this myself. Just discarded it.

Andrew
 

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I have this purple headed moisture missile type thingy, but I suspect that if I clamped it into an u/w camera housing consternation would ensue.

There's a wet sensor in an Amphibico housing I have which relies on a couple of wires, a battery and an LED. However instead of wires they've used a couple of flattened strips of copper (more surface area), and placed them at the very bottom of the housing. When you replace the battery at timely intervals it works very well. If you're a twat and don't replace the batteries when you should, it doesn't work when you most need it to. Which is why I have a lovely 100m rated Amphibico housing and no camera to put in it. If you except the salt-corroded slagheap in the corner that is  
 

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Thanks guys,  I have found one circuit diagram.  

And now having identified the rectifier in the diagram might give it a go.

Here is a link to the circuit if interested.  

Moisture detection circuit
 
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