Foam Switch?

You can go for pressure transducer, which are readily available in market. This acts likea switch

thanks

Rajiv Mehan

You don't state what sort of power you want to switch, but a few simple low power switching mats can be made with a layer of standard foam rubber with gaps inbetween two outer sheets of durable plastic, so any pressure compresses the foam rubber until the two sides meet, they should have a conducting surface on them, of course.

If you want a more analogue type of switch to give an output dependant on the pressure applied, I made on some years ago where I used anti-static conducting foam rubber as the filling in the sandwich..... the resistance between the top layer and the bottom then varies as the foam is squashed....

Any use to you ? ........ John.

Thanks for the feedback. I'm looking into a few of the suggestions.

Analog vs. digital doesn't matter too much. As I stated I am just trying to determine if foam is compressed at all. So if it was analog, I could just set a low threshold value for when it is compressed.

Are you seeking a chemical activator for the foam to expand?

Depending on force, load cell technology could be used. It could be molded in and sense the compressing force inside a foam layer.

If suitable for your application, I would suggest you look into a pressurized bladder in place of the foam, which also makes a great adjustable gasket/seal that can be used with a pressure switch - or for analog output, a transducer - possibly try a search on globalspec.com

All these replies are kind of a waste of everyone's time (no offence to those who took time to post ideas; thank you, they will someday hopefully help the next person to search the threads) unless the OP can tell more about thier application.

Is it a "digital" or analog type switch? what cost range/EAU are you looking at? What sensativity are you trying to attain? What is the switch's stimulus? (What are you using as input?)

If you don't know then hopefuly I'm wrong about my statement above and you will research most of those wildcard suggestions to see what's out there, and base the rest of your system around that....

Try searching keyword "softswitch"

You may try a capacitance type device or circuit. Any displacement or change in distance from the top to bottom of foam would be detected as a change in capacitance. The capacitance circuit could then activate the switch output. You'll have to do a search under capacitance to see what is available.

Second choice would be to bond a metal contact to top and bottom of foam. Depending on the thickness of the foam, you would have to dimple the metal or provide a tee type extension to touch the other plate when the foam is depressed. There would have to be some slight clearance between the the tee extemsion and plate (0.005-0.010) in the static condition.