View Full Version : Universal Board
06-07-2005, 08:19 PM
http://www.jesseshunting.com/forums/style_emoticons/<#EMO_DIR#>/smiley-help-green.gif I have just put together my first digital IR unit and everything seems to work fine...thanks to everyone at Jesse's for their help and ideas. I used a D-360l with a Universal Board attached to the lid of my case. I haven't had a chance to test the distance yet, but I did notice it doesn't sense motion until I am straight out in front of it. What angle are they supposed to sense motion at? I thought that with a 2-3 second delay (usually closer to 3) that it should pick things up sooner, otherwise they're gone by the time it taked the picture. My PIR sensor is centered with the lens, but was wondering if maybe the board is too far back. Would this affect the angle? I emailed Bill and he told me to cut down the 1" spacer to 13/16" to get the 5/8" distance between the sensor and the lens. But then I realised there is also a washer and a nut under the spacers? Is my board too far from the lens? http://www.jesseshunting.com/forums/style_emoticons/<#EMO_DIR#>/smiley-confused-yellow.gif
06-07-2005, 08:56 PM
Probably thewasher, nut, and 1" spacers would put the front edge of the PIR way more than the .65" from the fresnel lens. Without the washer and nut the 12/16" spacers would put the PIR at the correct distance. So, measure the washer and nut as close as possible and cut down the standoffs so that the combination of the three items is 13/16".
Now, remember that the ridges of the fresnel must point toward the PIR on the control board. Smooth side out and ridges IN. Also, the angle of detection is 10 degrees.
Below is a chart of the detection are calculated on a 10 degree cone which is what you get with the .65 focal length LODIFF fresnel lens:
Distance to Target, (Calc. Detection Zone ), Rounded Detection Zone
10 feet: ( 1.749774 ) 1.75
20 feet: ( 3.49954 ) 3.5
30 feet: ( 5.24932 ) 5.25
40 feet: ( 6.9971 ) 7.0
50 feet: ( 8.74886 ) 8.75
60 feet ( 10.49864 ) 10.5
70 feet ( 12.24842 ) 12.25
80 feet ( 13.99818 ) 14.0
90 feet ( 15.74796 ) 15.75
Right Triangle Calculation Tool (http://www.webmath.com/rtri.html)
Although this site calculates the flat sides and angles of a right triangle we can use it to project the width of the cone of detection at the end of the target distance by calculating the length of that far leg of the triangle away from the angle and doubling it.
I inserted 5 degrees for Angle E( half of the 10 degree PIR cone). I then entered a ? in leg a ( looking for half the radius of the cone at the desired distance ). I then entered variable distances in leg b ( distance to target ). Then hit the GO button.
The result is the radius of the circle at the end of the cone. So, to get an acurate 10 degree cone we need to double that for the diameter of the end of the detection cone.
Hope this helps
06-07-2005, 09:29 PM
Is that 10 degrees to each side or 10 degrees total coverage? That doesn't seem like very much....I guess I'm used to using the MS20 sensor which has such a wide angle of detection that I have to put tape on the sides to narrow it.
If those numbers that you posted are correct, assuming I don't want my picture much further than 20 to 30 feet away, that only gives me a zone of 3-5 feet to trigger the sensor. That beeing said, a deer walking by will have to be in the center of the camera frame before it is detected, then a 3 second delay will occur, then a picture of the back end of (if you're lucky) the deer will be the result. This just seems very strange to me, but like I said, this is my first digital and pix board.
Thanks for the tips, I'll play with the spacers a bit more and see what happens. I'll let you know.
06-07-2005, 09:47 PM
That is 10 degrees total. I use this lens with my cams and the pix boards and it is the cameras that dictate the time to shutter.
If I setup on a trail I use the angles and point the camera on a bit of an angle where I expect them to come down the trail. This way they are in the middle of the detection zone longer. Also, rubs and scrapes keep them longer in the detection zone. Mock scrapes are used by many to draw them in and get them to stop.
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