I need to make a backlit plexiglass box, with images on it. If you put your hands on the right images it can detect that and then that will do something else.
I'm struggling to figure out how I can detect the hands in the right place.
Capacitive sensors seem to be right, but they would cast a shadow right?
Any help is appreciated,
Gilligan
How are you making the images?
Weedpharma
Probably printed backlit adhesive vinyl.
That's cool.
Would there be any sort of proxy sensor that would go through vinyl and plexi?
Not sure i understand the question.
The film is conductive and fairly transparent to light.
A lot of cooker hobs with glass surfaces for instance use capacitive pickup but depend on mains ac voltage being present to work.
My concerns with the transparent film is how to turn that into something that works as a switch behind plexi.
I need this behind a large say 2'x4' display where someone would need to touch 4 sensors at once, one at the top, two in the middle and one at the bottom.
Make 4 buttons with the film.
It needs to be 'etched ' somehow like a pcb.
Then use a capacitive detector ic , the type made for hobs.
Just a thought i recently acquired a vinyl / stencil cutter , perhaps that would work to trace out a circuit.
I could probably do that. Wife just told me she wants it about 6' x 2' so they will be spread out a good bit.
Wouldn't IR pass through acrylic/polycarbonate and backlit vinyl?
If light passes doesn't infra red light also pass?
Embed infra-red LEDs and photodetectors in a thin frame around the sheet and detect when the 'beams' of infra-red light across the front of the sheet are interrupted.
Archibald:
Embed infra-red LEDs and photodetectors in a thin frame around the sheet and detect when the 'beams' of infra-red light across the front of the sheet are interrupted.
That's not a bad plan, I could essentially do a matrix of them and the right combination of off and on would be what it would take.
Its possible to etch ito like a pcb, i do not know what to use as etch resist though.
Boardburner2:
Its possible to etch ito like a pcb, i do not know what to use as etch resist though.
Referring to the possible use of the conductive transparent film, I do not understand why you would need to etch it. Couldn't you simply use four pieces of film each say 100mm x 100mm? The issue is connecting to the film invisibly unless the pieces are at the edge of the panel.
As that ITO film is 0.175mm thick I wonder whether its edges would be visible (unless hidden by the artwork).
I have been using an MPR121 touch sensor breakout board (with insulated buttons) and would recommend it for use with the ITO sheet. You can set its thresholds but I have not tried it working through the thickness of acrylic sheet.
It would be good to have invisible extremely fine conductive traces of e.g. gold on the back of the acrylic sheet to be used for capacitive proximity sensing. However that's unrealistic except as an industrial process.
Archibald:
Referring to the possible use of the conductive transparent film, I do not understand why you would need to etch it. Couldn't you simply use four pieces of film each say 100mm x 100mm? The issue is connecting to the film invisibly unless the pieces are at the edge of the panel.
The film is a 'solid' conductor the purpose of etching is to give different lands that can be used as isolated differentiated sensing areas (buttons if you like).
It s possible to make the connections outside of the bezel area so they are invisible.
Using bits like you describe would work but they have visible edges and i thing the op wants to backlight which makes it worse visibly.
Look at a smartphone or ipad you cannot see the traces.
Easy in mass production but not for the hobby market.
Addafrit sells the base material which in itself is quite a plus, this used to be unobtanium for the hobby market.
Boardburner2:
Addafrit sells the base material which in itself is quite a plus, this used to be unobtanium for the hobby market.
The box is to be 6 feet by 2 feet:
Gilligan:
Wife just told me she wants it about 6' x 2' so they will be spread out a good bit.
I guess the film could be laser etched . . . . but would it show?
Archibald:
The box is to be 6 feet by 2 feet:I guess the film could be laser etched . . . . but would it show?
the box is 6 feet by 2 feet.
Is thsi he size of he display?
It is to mimic a stain glass window that is 6' tall and 2' wide, it will be the only light source in the room.