Sensor Hole size

ArkansasElkHunter

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I did a little math and with the sensor located 1.05" from the lens (which is where I found to to be the most sensitive) the thoeretical field of view for the sensor looking through a 0.5" hole is 27 degrees or 14 feet wide at a distance of 30 feet.  A 0.25" hole limits the field of view to 14 degrees or  7 feet wide at the same 30 feet distance.  

The glolab lens is supposed to be a 10 degree FOV.  and some comercial mfg advertise about a 6 degree or 4 feet at 30 feet.

Has anyboby tried the smaller hole size.  It should give more of a rifle effect than a shotgun.  just thinking, any comment?
 



gabbyone

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I was wondering if  we could make a small pir hole and put a bright light in the cam case {like a ammo can}   and check it in the dark so see how far out it would cover.
 

davered1

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ArkansasElkHunter,

Are you taking into consideration that the pelican case is 4 mm thick, Elec box is 1/4" thick?

Does it restrict field of view already with the tunnel effect?

let me know
 

Constitutionalist

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I run tests before deployment.  I tape off the sides of the hole until I get pictures taken in the middle of the frame.  The only problem with this is "fast movers" in close, where I walked about eight feet in front of the camera,  I was off to one side of the picture.

I set the camera on a trail where the trail is about twenty feet out.  Allows for centered pictues with the subject squarely in the flash.  

Now, if only the snow would melt above eight thousand feet, I could get mine deployed.  Darned near got my truck stuck last weekend blowing through those four foot drifts (did I have a shovel in the back?  Of course not...)
 

Passthru

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 I just recently rebuilt one of my cams into a metal first aid box,useing the MS20 i made the sensor hole 1" wide by 3/4" tall,to trigger the sensor you have to be almost directly in front of the unit,the range is about 30' but it will not pick up every time,at under 30' it picks up every time.not sure if it will be what i like or not,i pick up the camera tommarow,or at least swap out the film.This is the same cam that i used the flashlight cone in for the flash,so im testing 2 things at once.
 I have it placed 20' away from a trail heading to my feeder.I like the MS20 sensor for 2 reasons,it is sensitive and cheap,but it is too sensitive so im hopeing this set up will work better.I do know that i can crawl under the cam without triggering so the little critters should not be a problem,but it could cost me a pick of a bobcat or something like that??? we'll see this weekend.
 

ArkansasElkHunter

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Davered1,

1/4" thick material would reduce the FOV to 22° fo the 1/2" hole and 11° for the 1/4" hole.  These calculations assume a single point of intersect on the PIR lens.  Since the lens is actualy .1" wide the FOV may be a little larger if you assume the IR light will intercet the PIR at the oposite corner.  I'm gonna pull the sensor off tonight and try wiring it to the board anyway tonight.  I'll try a half inch hole and see what happens
 

INshedpicker

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This is a total shot in the dark, but I'll toss it out anyway.  I'm sure that not all fresnal lenses are created equal, right?  So, could not the actual design of any particular fresnal lense be a limiting factor as to what size hole it could be used with?
 

Rooter

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Does anyone know.  Is the long bars on the MS20 (top ones) designed for the longer range?  If we want to shorten the range can't we just shorten those bars by partially covering them up?  I searched the board and couldn't find an answer.

Rooter
 

ArkansasElkHunter

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Rooter,  sey on the long bars.  there is a diagram that jessie posted in modifying the ms20 senssor.  the direct  focus at a higher elevation tham the shorter ones.  the shorter fet ones point towards the ground so to speak.  with the hole size they would still have the same side to side FOV.

MS,
yes the Glolab lens is advertised as a 10° fov lens.  They have a circular pattern on them if I remember right from Brian.  I think it's two or three bucks each.  There is a link posted somewhere. do a search for glolab.  I'm not sure about the other two mfg. that Arch posted about.
 

Rooter

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Question... Instead of messing with moving the distance from PIR to fresnal lense on the cams to cut the sensitivity wouldn't it be easier to block part of that top band in the lense.  The cam could be then aimed at a downward angle toward the ground to obtain a set distance.  A cheap laer pointer could be mounted in the case to show the aiming point.  I have been meaning to try this.  Do you think it would work?
 

ArkansasElkHunter

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Sure, most guys use tape or something to restrict the horizontal FOV.  It shound work on the vertical as far as limiting how far it will reach.  The will be more like having a baseball cap on pulled down over your eye though.  Some people are wanting the sensor to be less sensitive to small animals as well as limit it's range.  Yea the laser should work.  you will probably have to power and switch it seperatly.  I want to try it too just for grins
 

Brian

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I tried the laser pointer with the camera I built with radio control.  The sensor would transmit a signal from the ground to the camera in the tree to take a picture.  I used the laser pointer to try and aim the camera so I would know it was pointed right.  The only problem was that the laser I was using could not be seen in broad daylight from more than a couple feet.  It worked fine in moderate light or inside but outside the daylight would wash it out.  So make sure if you get one that it can be seen in broad daylight and most cheap lasers cannot.
 

Hill Hopper

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Brian, don't know if this would work or not, and could be a little bulky, but a box, or something with a shadow should work to put in front of it to see a dot. Just a thought.

Butch
 

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