# Motion sensing head looks in direction of movement?



## bluebledthesea (Sep 18, 2007)

I would have to save this one for next year, but are there any tutorials out there for creating a creature with motion sensors so that they look in the direction of the movement that sets them off? For example, if someone walked by the creature, the head would basically follow them. I haven't found anything like this yet, but I'd be interested in reading about it. Thanks!


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## Sickie Ickie (Jun 20, 2006)

I know the non-tech way is to use a negative face, but I'm also interested in the electronic way.


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## Otaku (Dec 3, 2004)

The Alive chimpanzee has sensors that will move it's head to follow a nearby person, but I'm told that one has to be very close for the sensors to work at all.


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## Frighteners Entertainment (Jan 24, 2006)

I've installed security cameras that do that. Pretty cool.


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## JohnnyL (Aug 17, 2006)

I saw a motor on some website that is designed to do that, but the price was WAY too high.


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## Shakes (Sep 6, 2007)

i have a few skeleton faces with large eyeballs I bought a few years ago - The eye balls follow you as you move past it. It say's something like "who goes there" and a few other lines. When I pull down my stuff on Oct. 1st I'll see who makes it. I think it was done using two motion detectors.
:zombie:


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## gadget-evilusions (Jan 26, 2007)

Here is one you can buy if you really wanted too.

http://www.monster-tronics.com/product_info.php?cPath=23&products_id=38


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## Hellspawn (Oct 13, 2006)

theres gotta be a way to do that for less money....... I just cant figure out how


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## Richie (Jan 4, 2007)

Someone I know did exactly that on a full size robot. I'm having difficulty contacting him because his website is down. But he used PIR sensors and actually wrote the code onto OOPIC components. As far as I know, it worked very well. The Monster-Tronics version, I have no idea what makes that work or how well it works. But for the price, I'd say it costs about the same as using OOPICs. Is anyone going to purchase the Monster-Tronics head?


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## bluebledthesea (Sep 18, 2007)

Yikes, I was hoping for an inexpensive, DIY solution as well!


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## Dark Lord (Jul 25, 2007)

(As Frighteners Ent.did) You can the use fake security cameras that have motion sensor & follow.Just mount a head on top of it, you can get them pretty cheap,I've seen them on EBay, 4 for 35-40 plus shipping.


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## Death Wraith (Mar 23, 2006)

I imagine it could be done with 2 (or more) PIR sensors running to a prop-1 with a program written to trigger a servo based on info from the sensors. I'm not much for writing code though. Maybe some one else can address?

DW


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## Dr Morbius (Sep 21, 2004)

A PIR is just a switch. I doubt any feedback circuit could be built from one, any more than one could "code" the info from a light switch.


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## Death Master (Jul 1, 2007)

I have a new prop I'm just about done with that has a head that moves left or right and center buy using 3 sensors I plan to have my prop by the sidewalk so I needed a way for the head to turn in the direction the kids where walking from, so I used a left, center, right IR. diffuse sensor you can use PIR or mat switchs if you want to they just act like switch's, so when the kids reach the first sensor the head turns in that direction, then when the kids reach the middle the head gos to the middle position, and when the kids reach the last sensor the head ends in that direction, its not a cheap way to do it ,but its the one way I do it.


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## Death Master (Jul 1, 2007)

You can use three PIR sensors and code it to track a servo, the sensors have to be mounted to the servo, lets say the left sensor picks up movement you code the servo to turn left until the center sensor picks up the movement, then you stop tracking the servo until the right sensor picks up the movement then you code it to keep tracking right, until the center sensor picks up the movement. I'm sure the head movement would be a little jerky, but If you code a buffer in, it would smooth out the movement.


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## Sickie Ickie (Jun 20, 2006)

still mucho moola though.


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## Evil Bob (Sep 1, 2005)

Sometimes having an actor is better than a prop.


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## TommaHawk (Sep 18, 2007)

Fewer components = cheaper solution. I bet it could be done with two motion detectors, a DC motor and two limit switches. Once one side detects motion it sends power to the motor, turning the head, until it reaches a limit switch (killing the power to the motor). Reverse the polarity of the wires coming from the other detector so when _it _detects motion it reverses the motor until hitting the other limit.

Problems:
-You only get side-to-side motion, not centering. There's a wiper motor out there that will always return to the same position once power is cut - maybe you could work that into a centering position.
-No true "tracking"
-Is it hard to limit the side/side visibility of motion detectors? You'd need to make sure the fields of vision didn't overlap in the center.

Cheap is relative - I doubt tracking could be done for mere peanuts.


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## Hellspawn (Oct 13, 2006)

TommaHawk said:


> -Is it hard to limit the side/side visibility of motion detectors? You'd need to make sure the fields of vision didn't overlap in the center.


You could always cover the portion of the motion detector that you didnt want to detect, I have done this by placing a piece of tape, spraypainting the lense, then removing the tape.

its great when you only want the motion detector to trigger from a very specific spot

IE: hand goes for the candy bowl, ect


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## Richie (Jan 4, 2007)

Death Master said:


> so when the kids reach the first sensor the head turns in that direction, then when the kids reach the middle the head gos to the middle position, and when the kids reach the last sensor the head ends in that direction, its not a cheap way to do it ,but its the one way I do it.


Hey Death,

What would happen if a kid reaches the middle sensor and is about to step on the last one, but another kid behind him/her steps on the first sensor?


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## Death Master (Jul 1, 2007)

Richie,
I have the head programed to stay with the last sensor trigged.


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## Richie (Jan 4, 2007)

That sounds great. Can't wait to see a video of it in action.


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## Xpendable (Sep 19, 2006)

You could also use a web cam (mounted in a fixed position) and use software to convert motion detected into servo movements. I think there's some open source projects out there that do the motion tracking part. It would give you x,y coordinates of the area within the image seen by the web camera where motion was last detected. They detect motion by comparing a previous image to a current image and seeing what areas have changed.


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## .id. (Jul 3, 2006)

Seems to me that you could use 2 PIRs and a solar tracking circuit (like this one). This one is designed to run uattended and automatically reset when it hits the limit switch. I think you could also do this using a prop-1 or the likes....Anything that will do Analog to Digital Conversion. Just compare the values of the two PIR's and which ever one is greater turn the head in that direction. I've built solar trackers in classes before, but never used a PIR. The theory is the same.....PIR's just use a selective wavelength.


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