Capacitive Sensor Question

[danbrookwell]

I have a special effect that is triggered by someone stepping on an aluminum foil plate that is on the floor which is connected to a capacitive sensor which then goes to the effect's computer. When I put a small piece of foil on the end of the sensor, the sensor works fine (I touch the foil and the effect goes off), however when I put a big piece of foil (appx 7"x5") the sensor jus stays in the on position and the effect wont stop because it keeps getting a signal from the sensor. This has been a big headache and any help would be greatly appreciated since googleing proved a failure.

Dan

 

[MPowers]

Your statement reminds me of the old joke, Doc, it hurts when I do that! Then don't do that! ..... If the large piece of foil doesn't work, don't use a large piece of foil! Perhaps the larger piece doesn't have the resilence to rebound from the step pressure, ...just thinkin'.

My thoughts are:
1. Why do you need the large piece of foil??? Just use a small piece, that seems to work.....Right??? Am I missing something here?
2. use a pressure plate/N.O. momentary switch. Why the capacitance method?

Explain the gag a bit more thoroughly. When talent triggers the bit by stepping on the activator, does he remain on it or does he move on? If he remains on the trigger, you need it to trip a timing relay. The timing relay then can be set to wait from 0 to (a long time depending on the relay) to switch on and will latch on or, at a specific time, turn back off, even if the trigger is still depressed. Most can be programed to stay off after the first trigger so if talent steps off and back on the gag FX doesn't repeat.

Just out of curiousity, what is the FX?

 

[danbrookwell]

The effect is for a walkthrough attraction I am a part of. When guests step on the foil, they trigger the sound to play in that specific room. The reason I need a large foil piece is because i want to fit it under a door mat and I need something big enough that I can be sure each guest will hit it with their foot.

 

[MPowers]

Hmmmm?? OK, the FX doesn't turn off. Public still standing on the mat? Or, several people in a group stepping on it in succession? or......???? How many people are coming through at a time? A foil trigger does not seem to be robust enough for the application or it would work. I'll repeat one of my original questions, why use a capacitance trigger rather than a simple switch? Also, instead of having the foil trigger the FX directly, why not use a timing relay to control the results of someone stepping on the "foil" and triggering the gag?

Other possibilities, make the entire door mat a pressure plate. Get a piece of 3/16" plate, 24" x 36" (or to suit your door mat) and put it under the mat. If it is heavy enough to trigger the gag by itself, put some strips of 1/4" carpet padding around the perimeter until the balance is neutral.

Just thoughts.

 

[derekleffew]

Switch - Floor Mat - 14 Inches x 30 Inches

 

[danbrookwell]

Correct me if I'm wrong, (i didn't build the circuit so I'm not really sure how it works) but the tin foil is connected to a sensor which has a screw going through the foil and back into itself. I looked everywhere online and it seems to be a capacitive sensor. The sensor has a light on the top of it to indiciate whether or not its being triggered. My issue is that the light stays on when I have a large piece of tin foil, however if i put a really small piece on it works just fine (i touch it and the light goes on, and goes off when i let go)

 

[MPowers]

I'm not sure about this but I think the larger piece of tin foil is changing the capatance. The result is a much longer delay time before it stops conducting to recharge. Try changing the size of the foil in small increments. If the light stays on longer with each increase, there's your answer.

I maintain the real answer is to "switch" to a switch.