Toch sensor suggestions

Looking for advice on some touch/pressure (not sure if pressure only means barametric pressure) sensors. I don’t need the sensors to do anything difficult like variable pressure just when when something is resting on it or not. I would also like the sensors to be as thin as possible. I saw one video somewhere with a touch sensor that seemed to be the thickness of a sheet of paper. Any suggestions on a particular brand/type of sensor? Also can anyone clarify for me what the proper term is pressure or touch sensor?

Thanks!

http://www.parallax.com/Store/Sensors/PressureFlexRPM/tabid/177/CategoryID/52/List/0/Level/a/ProductID/384/Default.aspx?SortField=ProductName%2cProductName

thats one pressure sensor, a bit expensive though, but if you have some conductive foam, you could do this on the cheap.

http://www.instructables.com/id/DIY-Force-Sensitive-Resistor-FSR/

also, cherry switches may work.

That first sensor was the exact type I am looking for however I thought they would be a little less expensive. I need 20 for my project. I guess I could also look into using proximity sensors of some kind but I want something that would work in a variety of lighting conditions.

This: http://www.lynxmotion.com/Product.aspx?productID=627&CategoryID=8 might be more up your street. I bought a handful, but haven't gotten round to trying them out yet.

Capacitance sensing is another option, but might need more experimentation than you have time for. Capacitance only works with particular materials, although you can fashion the sensor out of most conductive materials (tin foil, etc). I've only done it with dedicated IC's, which can often do many buttons at once.

Hope this helps. :)

That is exactly what I was looking for...except for price ouch $5 for that little thing. I was hoping that I could find some sort of sensor for like $.50 or so. I am also looking at buying a crap keyboard and taking it apart to see if I can get individual sensors out of it. Again I don't need anything fancy like accurate force I just need to know if an object is sitting on top of it or not.

Thanks

How "thin" does thin have to be? How about an LDR or phototransistor?

If your just looking to see if something is sitting on something, you could just use some microswitches. http://www.sparkfun.com/commerce/product_info.php?products_id=97

Looking at the phototransistor method I have one question. Can they act like a on off switch? By that I mean how does the arduino handle input that is not HIGH or LOW because of the phototransistor putting it somewhere in the middle?

Question about the micro switches. How much force does it take to push them down? Also are the micro switches loaded to always return to the off position or does it lock into place once pressed and require another press to release it?

Thanks

A microswitch will spring back when you let go of it. They're spring loaded. As for the force required, that depends on the type of microswitch. Some types have quite low operating forces. Other types, particularly the ones with high current ratings, require a stronger force.

Cool then it seems like microswitches might be the way to go I will get a few to experiment with.

Thanks

You might also want to try something like this limit switch. Im sure you can find some less expensive then this one at radio shack. It is spring loaded, and is much easier to press down. http://www.radioshack.com/product/index.jsp?productId=2049718