Let's Make Robots!

Moving eyes behind a painting... Reminds me of one of those old 40's or 50's movies.

Eye Movements

One of my nephews said he had the idea of doing a painting with moving eyes that  would follow a person walking past.  He planned to put it at the bottom of a dark stairway, such as going down into the basement.

This is the circuit I gave him to accomplish it. It is a simplified way without requiring elaborate face recognition, etc. It just locks onto any object nearby and follows it with the eye movement. It only gives the illusion that it is following the person, but that should be sufficient for the effect he wants. It would be necessary to hid the ultrasonic uint in a way that it could not be seen, as it has to move back and forth to spot anyone nearby.

Also, I showed using a 28X2 controller, but a smaller one would do the job. —Even an 8-pin one could do it.

(I specified the 28X2, because I just happen to have some 28X2 picaxes laying around and considered he might ask me to send him the parts he needed to build it.)

Anyway, I thought I would post it here as well. It might give someone some ideas for their robot.

ADDED (13JUN2012): Here was an idea I had to hide the sensor by making a special little "Name Plaque Holder" with the sensor and servo inside (Servo attached to inside top of box, so sensor would be closer to the bottom and all inside painted flat black. Padding to be added as needed to quiet the servo.


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Dampen servo noise = slow down servo movements...for example

Whether either IR or Ultrasonics (or UV for that matter) can pass through the painting will be the subject of testing. There may be different things to consider: acrylic paint versus oil paint for example, or whether particular colors will allow more signal to get through.

As to dampening the servo noise, I think that will be alright. The servos themselves could be wrapped in some foam-rubber and the painting itself may dampen the sound of the one moving the eyes, plus the other one, if it is mounted in a box, the box could be lined inside with sound deadening material also.

Regarding the embedding of the sensor into the eyes here some thoughts: 

When you want to track an object with only one reflection sensor like the ultrasonic you need to find out where the object is.

Therefore the sensor must rotate from left to right and right to left to scan the area (see picture). Each scan results to a depth that you use for further calculation. The scan that results to the smallest depth has the direction of the object (that is scan 4 in the picture).

This scanning must be performed periodically to notice a moving object.

So now when you embed the sensor into the eyes that might lead to oscillating eye movements. This is not natural. It is therefore a good idea to encouple the eyes and the motion tracking sensor. Now the eyes point to where the sensor calculated the closest distance to the object.

You would probably need more than one distance sensor to detect movement from right to left so the eyes could follow it. The multiple PIr sensors are what I used in servo (just 3 in that case, but for this two might actually do the trick.) what about Oddbot's array like they use in the Little General? Would there be enough range?

Since I considered the sensor swinging back and forth, only one is needed. Also, infrared is an alternative to the ultrasonic. Either could be used. (Including OddBot's "eye" unit.)

The only type sensor I ruled out was an X-band radar unit, which would pass through the painting perfectly but while it detects motion, does not return precise distance and direction readings. The units as they are made have too wide a field of view to get a proper direction reading to aim the eyes well.  The X-band unit could actually be used, but would not give as good of results for what is needed.

I think the PIR units have a wide field of view also.

This eyes in a painting is in my mind too for quite a while. Neat solution you present here. Thanks for sharing. Collected.