Light sensor Interface

[bashekraai]

Hi everybody,


I’m working on a project and want to make a device which enables you to browse wirelessly and contactless through different slides in a slideshow. The idea is that you make some gestures like making a swype kind of movement horizontally with your hand from the right to the left to go to the next slide.


I’ve already tried to do this with a leap motion, (https://www.leapmotion.com/) but this turned out to overcomplicate it a bit so now I’m trying to look for another way to realize this project.


The idea I have now is to make this with light sensors. I think that if I place two light sensors in a housing this can be the solution. It has to work like this: when you move your hand from the right to the left over the housing, the sensors will notice that the right sensor gets dark first and then the left sensor. A computer has to recognize this as a gesture and ‘plop’ the next slide will be shown.


My knowledge in electronics is not that good and I think I have to program some software to run this thing. Does anyone have tips or suggestions for this project? It will be appreciated a lot, thanks in advance!

 

[KrisBlueNZ]

Hi there and welcome to Electronics Point

That's an interesting idea and I think you may be able to make it work. I would be concerned about nuisance activations though. You would need to be able to detect a fairly specific sequence of events - a rapid and significant drop in light on one sensor, followed by a rapid and significant drop in light on the other sensor, followed by a rapid and significant increase in light on the first sensor, followed by a rapid and significant increase in light on the second sensor.

This is a suitable application for a small microcontroller. You didn't say what programming experience you have. If you don't have any, for simplicity of programming, you might try a PICAXE (http://www.picaxe.com), which can be programmed in a BASIC-like language and will probably be fast enough for this application. Alternatively, any small microcontroller such as a PIC or AVR would be suitable. Or you could go for a complete board, with power supply and I/O devices already built, such as an Arduino, Raspberry Pi, BeagleBone, etc. See https://en.wikipedia.org/wiki/Comparison_of_single-board_computers for a list of possibilities.

You need a board with two analogue inputs (for the light sensors) and probably two digital outputs to control advance/reverse on the slideshow. More inputs and outputs might be useful for configuration and operating mode setting, and other features you might want to add later.

 

[hevans1944]

This is an ideal project for wearable, wireless, electronics. Just fit a few MEMS accelerometers orthogonally to a wrist cuff. Use an embedded microcontroller in the cuff (see attached PDF file), or at least connected to it if located nearby, to read and interpret the analog accelerometer outputs, sending the digitized accelerometer signals to a remotely located computer controlling the slide projector. A Bluetooth connection would be an ideal communication link. Also visit this Google result. At the remote computer you will need a hand-waving detection algorithm that will recognize a suitable gesture, as detected and reported by the accelerometers. Try using something unusual like a quick rotation of the wrist with simultaneous motion of the forearm upward or downward.

Some experimentation will be necessary to discover a (perhaps unusual) arm motion that does not normally occur while discussing the currently projected slide.

Oh, and welcome to Electronics Point! Enjoy your visits here!

 

[Gryd3]

One other possibility is to ignore the 'swipe' feature and simply have a proximity sensor on the left/right edge... a simple 'tap' like when browsing images online.
You could also look at similar techniques used in 'VR headtracking' for your gesture controls...
It's essentially IR light, and a camera to follow it. You may also be able to use something like OpenCV which is an image recognition software that will work with video... Or perhaps you could explore using the Xbox Kinect for an unintended purpose... as it's used in lots of custom projects.

 

[hevans1944]

You could also use a Bluetooth "clicker" suspended from a lanyard or attached to the wrist. Just push one or more buttons to advance or re-visit a slide. Works from anywhere in the room, minimal programming to recognize button pushes. There are also other wireless devices, similar to automotive electronic keys, readily available. Maybe the KISS principle is valid here.

 

[Gryd3]

You could also use a Bluetooth "clicker" suspended from a lanyard or attached to the wrist. Just push one or more buttons to advance or re-visit a slide. Works from anywhere in the room, minimal programming to recognize button pushes. There are also other wireless devices, similar to automotive electronic keys, readily available. Maybe the KISS principle is valid here.

Good call. Depends on what the purpose is though.. contactless and wireless was asked for. I assumed that it would be for random guests or users to use.

 

[hevans1944]

Good call. Depends on what the purpose is though.. contactless and wireless was asked for. I assumed that it would be for random guests or users to use.

Yeah, we do presentations here at work using an LED projector connected to a laptop. There is a remote control thingy somehow interfaced to the laptop to select slides from a Microsoft PowerPoint file. It is not at all uncommon for new users to get confused about how to operate it. I kinda miss the old school overhead projectors with transparencies you could write on with a felt-tip marker. <sigh>