Thin Pressure Pads

there are systems that are designed to be placed between the subfloor and the floor joists.

I dont know where, but I once saw systems that were integrated into the vinyl itself.

I'd look at piezoelectric polyvinylidene fluoride films.

Polyvinylidene fluoride - Wikipedia, the free encyclopedia

Squeeze it, you get an electrical output.

If you're doing this as a one off, get a calculator keypad of similar from the local electronics shop, or even a cheap calculator and strip out the switch film from behind the keys.

Find a dead microwave and get parts of the control panel.

Find an auto wrecker and get a dash mounted "touch" switch.

They are all NO configuration. You will need signal amplification.

In Arm prosthetics we sometimes use a touch pad, its a thin switch, its expensive and is about as thin as a playing card.

Spacecannon

DIY - a laptop or keyboard membrane?
Go through some switch catalogues. (online or hard copy)

Does it have to be under the floor?
Have you thought about using light sensors / beams, e.g. one from the top frame
dividing the doorway space vertically in half? These can be set such one has to
enter to see it. i.e. they are triggered before being aware of it.
Even proximity switches can be hidden in door frames, etc.
(retailers use them in doorways to count the customers entering.)

I am only suggesting these because:

1) Under floor switches can be difficult to maintain (hence using mats.)
2) These are well know to intruders, and can be easily stepped over.

Hope this helps.

jt.

"Knock Knock. " (on the door)
- If that's the invisible man, tell him I cannot see him today!

Thanks for your reply, it's for a floor design I'm trying to make it interactive by standing on certain objects. I suppose I could use light sensors on the floor to react when they are covered by a foot but the foot would have to be on a specific part of the shape. I just thought by now alarm pressure pads would be up to speed and not so tacky looking.

In that case a resistive touch screen technology may be the way to go: you just need one big sensor and a bit of electronics to work out where the person is.

One problem: two people on one sensor will "confuse" the electronics.

EDIT....

Hang on a minute what about those mats they use for dance games on games consoles.

Thanks I've thought about that but again they are quite similar to the alarm pressure pads available. They are really baggy and would cause a problem under a flooring such as vinyl.

Some cars use very thin flexible pads in the seat cushions to detect if anyone is sitting there. They are what cause the nagging seat belt light to flash until you do up the belt. I know they are used in higher model Vauxhalls but other makes will have them.

Excellent reply, but my understanding is they are REALLY expensive......but of course they would work great!

Recently had to get one replaced in an Audi, €600,- (about $700 or so at a guess) with the hours as well!!

What also can be used is that thin conductive foam that is used to stick Semiconductor chips into, you can buy (be given it!) it quite thin. Or make up a "slicing board to take a thin "skim" off a thicker piece.

Place it between two pieces of aluminium foil and measure the resistance between the two sheets of foil.

When crushed, its resistance drops considerably. A simple single transistor circuit will usually be enough to detect the change.....

I did it once for the same reason many years ago but I found two things that made it unnecessary, the first was PIR sensors, the second was a house alarm system that does not need any sensors of that type it works on house resonant frequency and air pressure changes.....

I know what you mean, when I think of car parts I automatically think that I would be doing the work myself with parts from a scrap-yard.

What about a resistive touch screen overlay.

http://www.google.is/search?sourceid=chrome&ie=UTF-8&q=piezo

Thanks for all your replies, but my quest goes on. Am I thinking too far into the future again where it's too much to ask for an under flooring sensor not to resemble a puffy sleeping bag or a dodgy part of a microwave oven.

If you are after "heaps of them" then that's a different question. I had presumed that you were after a limited number for yourself.

If you're into manufacturing, then ask in that context. I could nominate 3 suppliers in Aus who would be capable of "membrane" sensors that would be less than 1mm thick, made from Polycarbonate film providing an on/off output with easily 100mA current capacity, shipped with peel off adhesive backing and ..... whatever features you want to specify.

They are the primary manufacturers for that sort of stuff. There are equivalents in the US, Europe and Asia and the types of devices we suggested be canabilised are what they make.

They will fabricate to your specifications.

LNI ADCAL (Aus) and Cadilac Plastics (US) are two that I've dealt with in the past but I would not want to be seen to endorse any specific supplier over another.

I completely forgot a better way to make such sensors, just add some strain gauges under the floor or even "in" the floor.....add some simple electronics to interface them and provide a signal.....

If you download some data sheets for strain sensors, there is often an example circuit for the interfacing.....search using Google.

If you want more detail from me, just ask.

This is the smallest lightest and best method I feel....