How can I create a sign that has components that rotate based on a persons proximity?

I want to create a sign that is 48"x 24" that is broken down into 4" squares. I want each square to rotate or flip so that one side has a message and on the other side is an entirely different sign. I want the squares to rotate at random so that they full flip to one side or the other.  The rub is the following. I want the sign to be spaced so that at a given distance (300 feet) the sign has one message. As the person walks closer to the sign, it is triggered so that the squares flip and a new independent sign is seen on the other side. 

I dont care  about material or cost (generally) I was thinking along the lines of the old train station signs in Europe that flipped over as trains arrived. However I I want the sign to be triggered by a individual getting closer or further away. SO  that if the person walks 10 feet closer to the sign, perhaps 3 more squares are flipped around, and if they go back in distance to where the started, the squares would flip back to the original point. I was thinking either passive radar or sonar, or lasers across points of embarkation. 

Please I need help!

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bwrussell29 days ago

There are lots of options.

You could use laser trip wires, like the ones that prevent garage doors from closing if they're blocked. A cheaper method for "trip wires" would be passive IR motion sensors spaced along the path.

You can get pretty inexpensive sonar units for micro-controllers but the needed range might necessitate using a couple along the path. You might be able to use IR in a similar fashion but instead of distance it would calculate the percentage change between readings and equate that to a human moving closer to the sensor.

iceng bwrussell29 days ago


Hack into a passive IR sensors before the on/off discriminator to get amplitude deviations and use several so modified sensors...

rickharris29 days ago

Ultrasonic is good up to about 6 or 7 meters.

Radar line of sight but more complicated.

Simple light detector a few feet.

Lasers - light not sure how you might do that except as said as a trip wire.

Whatever you'r into micro controller territory and programming.

For the display perhaps the easiest way would be to have the cubes / squares on rods and drive them with a small stepper motor again more programming.

You have a lot of design decisions to make, some may depend on your skill set or require you to gain new skills before you cam progress.

Pencil, paper and lots of drawing to work out the best way.

You could be better off considering an LED array in place of physical squares.