Sensor

Do you want the laser light to be visible as a beam? Otherwise just mount a lamp on the object so it lits up when a button is pressed.

Or do you want to aim with the laser at the object, means one laser for 15 objects.

That would probably need a photocell on the object and complicates matters a lot.

You will have to use a simple logic of while Video A is running no other Video will start.

I'd look into a couple museums to figure how they have done it.

Good luck.

Thanks for your reply.

Well as I want to engage the visitor, I intend to make the light visible. It will help visitors, especially children, to locate the object of their choice. In place of laser, any other coloured light will do. But the only problem in that is- the light should be strong enough for the objects are already kept in normal illumination.

Pease explain further what you are trying to sense. For instance, if you shine a laser on an object, its temperature will rise. Is that what you want to measure?

The very purpose of using laser is to locate the object of choice and nothing else. Usually laser lights are easily visible than normal lights. Thats the reason I propose to use the same.

Okay (maybe), but what are you trying to sense?

In Bangalore Visveshwaraiha Technical museum has many objects on display in a window. If a visitor wishes to know more about any object- he presses a button, selects it, a small LED light next to the objects lights up. You can start an audio to explain about teh object etc. Is this what you are looking for - a explaining about an exhibit?

My approach would be to use a rotary encoder with the laser pointer mount and a PLC or a micro controller like Arduino to keep track of the laser's angular position. When an object of interest is selected, the controller would notify the display which file to run. This would be a good project for a engineering student to help you with.

Note: A rotary encoder is an electronic device that transmit a a series of on/off pulses, normally a pair of pulses out of phase, as an engraved disk is rotated past a stationary sensor. The controller (PLC) keeps count of the pulses, adding or subtracting depending on direction, thereby "knowing" the angular position of the laser pointer.

you think thats actually going to register with this guy?

GA for the principle, but too complex so I did not award it.

Instead of an encoder, drop a vertical shaft from the light rotation mechanism. Fit an arm at a right angle so that it sweeps round in unison with the beam. Clamp 15 limit switches to a horizontal ring so that their position can be easily adjusted. Line up each object with a limit switch. When the beam is lined up with the object it's corresponding limit switch should be triggered by the arm. Wire the 'select' PB in series (AND) with the 15 parallel (OR) limit switches so you get one of 15 alternative signals when the button is depressed. Latch each signal with a two pole 1 N/O, 1 N/C, adjustable timer (pulse triggered one shot) and use the N/O contact of the timer to trigger the audio/video (A/V) commentary. Some A/Vs will run longer than others so set each timer at 5 seconds longer than it's video runs. Wire all the N/C contacts of the timers in series with the 'select' PB so that select is isolated while the A/V is playing. You can do this in hard wiring but a small PLC will cost about the same as 15 timers and the build time will be less. As suggested by others, a concentrated LED light beam will produce better results at a lower price than a lazer.

I don't think what you're asking for can be done with "low maintenance and basic skills", but perhaps an electronic hobbyist with a little programming experience could rig something up.

You need a PC with a USB digital interface (perhaps Arduino based) and light sensors at each of the objects. The interface would need 15 input lines for the light sensors and an output line which would switch power to the laser pointer. A program on the PC would read the sensor input lines, detect an illuminated sensor, turn off the laser, run the related video, and turn the laser back on.

Sense the rotational angle of the lazer light. A cam on the light's spindle to contact switches, Infared transmitter instead to recievers arrayed at angles

I would use a multi-node RF system with a master as the base and the objects would be nodes with assigned individual addresses.

I would install a light sensor on each object so that when the laser engages the sensor for a predetermined time the RF transmitter is triggered and continues to transmit until the light source is removed or the operator pulses the signal.

The master receiving unit would be attached to a small PLC that would be programmed to fetch the appropriate video and display it on a high resolution HMI screen.

More power! I would be more fun to vaporize the objects.

There's more to this than meets the eye, I suggest that first you read this paper on "what not to do", then Google on "museum interactive exhibit design" to see how others have done it.

As a docent it's you responsibility to make the exhibit engaging and easy to use, but you will need the help of some very motivated engineering students to make it happen.

You could use lasers, but you may not have to.

You can get simple an inexpensive LED infrared photoelectric proximity sensors called "retroreflective" that sense any object closer to it than the set distance. Some have a visible LED beam used for alignment. The beam is small and might be hard to see though.

http://literature.rockwellautomation.com/idc/groups/literature/documents/br/photo-br001_-en-p.pdf

If you need a brighter more visible beam, you could use a gun sighting laser mounted to the same thing that is moving the sensor, aimed at the same spot.

If it were me though, I would just back-light the object from below and turn on that light when the sensor sees it. By using an analog output sensor into a controller like a small PLC, you could "measure" the target distance and pre-program the controller something like "If distance = 3.32m, must be stuffed bear, turn on light under stuffed bear". This assumes that all of your objects are different sizes.

You have described an exhibit (one of 15) that can only be used by a single person/group.

So the other 14 will sit there dead while only one is in use?

Is this the intent?

Are you also going supply laser shielding for guest eyes?

Judging by your post and your replies, you are not experienced in the field of interactive displays, and neither am I.

BUT, I do know how to google and I found a mountain of helpful items just by typing in "interactive displays in museums"

you should try it, in fact there is a whole association built around this type of thing.

So try this link first: Museum Association

then is one: Huffingtonpost Interactive displays

Leachinspire Interactive Displays

and finally..

Heritage Interactive

Thanks a lot