>Magnet and Hall sensor. Analogue/digital, water-proofable. Cheap

What he Jinx said ^^^.

Also available as a 'turn key' industrial grade 'limit switch' (waterproof).

Or a 'mat' switch, as used in security systems under carpets
to detect intruders, or at supermarkets to open doors (not the
X-band radar openers now more common).


alan smith wrote:
> This is more of a proactive question, because I am afraid I may have to come up with a better solution that whats currently being used.  I am being asked to come and evaluate an existing design where "stepping stones" are used to initiate a waterspray sequence.  In other words, as you step on particular "stones" it triggers a controller input.  
>    
>   Presently the sensing is done using a load sensor that sits underneath a fake stone so stepping on it causes an analog voltage to change and thus triggers.  I've been there once under contract to repair, where the load sensor took a voltage spike and had to replace (about 1K ea) it and also fix wiring issues, realign things, and basically re-engineer some of the control features.
>    
>   That was last year, and now I am getting a call from the end user (it was the design house that contracted me the first time) to come and look at it again.  Can you tell I'm excited about this?  So I am wondering....anyone have other ideas other than a load cell that would stand up to lousy enviormental conditions (being flooded, baked, froze, etc) and would keep working more than a year.  The "stepping stone" is attached to a plate that has the load cell attached to it, so whatever is done has to be easily retrofitted.  Cost isnt such an issue since its not a production run but a one-off deal.
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