motion switch

[oliphant]

Can anyone help me to build a motion detector switch that will turn on a video camera when triggered.

Thanks

Olly

 

[magno_grail]

Why not buy a motion detector light switch and connect the output to a relay or whatever to turn on the video camera? Everything is all sorted and they have controls for sensitivity, range and duration.

 

[stevez]

Do you want the camera to come on or a recorder?

Something I've wondered about - it would seem that a video camera that is on is delivering an output that repeats itself constantly, if nothing in the field of view is changing. If something moves into the field of view then things change relatively quickly. I wonder if that change couldn't be detected/managed in software (possibly sound card) and used to trigger something.

 

[gerty]

Steve, we used to use something like you described years ago in the security industry. It was called VID-ALERT you would run the video cable thru thier 'black box' then to your monitor. The box had two pots on it to superimpose two vertical lines on the screen. Any movement between the lines, even a light switching on would set off the alarm . All movement outside the lines was ignored. The alarm was a set of dry contacts ,momentary or maintained, your choice..Don't know if they're still available..

 

[magno_grail]

Stevez-
They make video capture boards that allow you to compare frames pixel by pixel. Frequently used in TV guided missile targeting systems to locate and track a target. Software uses edge detectors and shape comparison routines to locate objects of interest in the frame.

 

[bmcculla]

You could make a simple analog circuit to integrate the NTSC or PAL signal from the camera each frame. A sudden change in the integrated value would indicate a change in the camera view. A simple microcontroller could read the Integrated value and trigger a alert signal to start recording. The microcontroller would also reset the integrator each frame. You could do all that with counter chips too if you felt like it.

 

[zevon8]

There are very reasonably priced video capture cards available that do everthing you need. Hauppage makes one, and several others, all based on a Conexant CX878 , BT848, chips or members of its family. There are quite a few software packages available for this chip, and one feature that is common is motion sensing capture. You basically define an area in the cameras view that you want to monitor, and any motion in that view will trigger the software to start recording.

These cards are used for computer based security systems that stream jpegs or MPEG2 video to the hard drive, and also allow remote monitoring via modem.

The same family of chips is used on many PC video cards for TV tuners, and is very well supported with developement kits from Rockwell/Conexant.