Science Buddies: "Ask an Expert"

I am doing a science projected concerning constructing a new controller for Playstation2. It requires a 3-dimensional field in which the player is within a 2.5 meter x 2.5 meter x 2.5 meter field. I was wondering what would be the best sensor to pinpoint exact movements and pressures within the field.

dhmai wrote:I am doing a science projected concerning constructing a new controller for Playstation2. It requires a 3-dimensional field in which the player is within a 6 ft x 6ft x 6ft field. I was wondering what would be the best sensor to pinpoint exact movements and pressures within the field.

Need a bit more info...
If you want to know where a player's feet were, you could use some sort of pressure mat. To sense motion, one way would be to put a little sound generator on the parts you were interested in and have pickups on the outline of the field so you could triangulate the sound.

OK, now what do you think?

Ceal Craig
Science Buddies
Ask An Expert

I think these are great! It's just that i do not know which sensors to use. I also have to be able to connect it to a breadboard/circuit board and program it. A person has mentioned to me about using Force Pressure Sensors and a friend of mine had mentioned Piezoelectric Crystals.
What information do you need?

dhmai2 wrote:I think these are great! It's just that i do not know which sensors to use. I also have to be able to connect it to a breadboard/circuit board and program it. A person has mentioned to me about using Force Pressure Sensors and a friend of mine had mentioned Piezoelectric Crystals.
What information do you need?

Do you need to know where the hands are? the feet are? Are you building a 6x6x6 foot area to test? or will there be a scaled down mockup?

The type of sensor you pick has a lot to do with what information you are trying to gather and the accuracy needed. Is cost a factor?

I'll remember to check back in a couple of days to see what you respond.

Sorry, I forgot to put

Ceal Craig
Science Buddies
Ask An Expert Forum

I have already taken measurements and assumed where they would be on the 2.5 meter x 2.5 meter x 2.5 meter area to test.

I should have thought of scaling, but I have not.

I was thinking instead of using just one type of sensor to get all the information i am trying to gather. I am planning to use multiple sensors.

For an example, a piezoelectric sensor on the floor would take up all the foot movements on the ground, however, I do not know what they are called. I know what they look like. They are quite similar to the Dance Dance Revolution (DDR) dance pads. The DDR dance pads have a thin layer of a material with spaced out holes. The material is placed in between two film-like substance which contain an element or compound ( I am assuming carbon). The material is placed in between to close of the connection. When they stepped on in a particular area, they connect through the holes in the material in between them.

Another thing is the cost factor that i am worried about. I have access to money, but I do not wish to use it carelessly and not being able to return the parts did not need.

Thanks!

Hi folks,

Hope you don't mind me jumping into the conversation with a couple thoughts.

Dhmai, I'm sure you can buy ready-make pressure sensitive mats, but you might well be able to make one yourself for much less money. From your description, it sounds like you've got a pretty thorough design for how to build one.

I haven't seen a DDR pad, but your description sounds a lot like the way many sealed push-button panels and the buttons in cheap plastic keyboards work. Most of them use either conductive plastic or metalized plastic sheets for the outside layers, and they work exactly as you discussed.

If you hunt around, you can probably get hold of similar material. Try searching for "conductive plastic" or "conductive elastomer". A trade name that you might find useful us VELOSTAT, which is 3M's name for their line of conductive plastics. You can buy it in thin sheets for around $5-$10 per square yard, although you may have to hunt around to find someone willing to sell you less than a 150 foot roll of material. (One of the cheapest small-quantity suppliers seems to be these guys: http://www.lessemf.com/plastic.html - I hesitate to point it out since their web site also contains some totally bogus science. The product is real, even if their reason for selling it isn't. Just don't take anything they say too seriously.)

Keep in mind that even the most conductive plastic isn't nearly as conductive as a metal, so you'll probably not be able to use a large plastic pad as a switch to directly drive the input to a logic circuit.

There are some other products, like metal foil tape, aluminum coated mylar sheets, and conductive caulk that could be useful and are pretty cheap. I'd be happy to point you to suppliers if you have trouble finding them. (We use that sort of stuff all the time in our lab for keeping radio frequency interference out of experiments.)

With a bit of ingenuity, you could also find a way to make something work using more readily available materials. For example, one could stack two rectangles of upholstery foam, cut a slight recess from the surface in one to make a hollow cavity, and glue metal foil to the top and bottom wall of that cavity to make a switch which closes when stepped on, and then stiffen the top with cardboard or plastic so that one doesn't have to step right in the center of it.

You could also make something by applying metal foil or by gluing wires to the surface of rubber or plastic sheets.

Finally, here's an example of a home-made pressure sensor using conductive plastic and strips of metal, which is kind of neat even if not entirely relevant. ( http://www.pulsar.org/archive/int/timsw ... ostat.html )

Take care,
Erik

Sounds like great advice!


Ceal Craig
Ask an Expert
Science Buddies Forum