Fresnal lens Allignment

ArkansasElkHunter

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I did a little playing around last night and thought I'd share it with you guys.

First off, you can take a black majic marker and "Black In" the Fresnal lens if you want.  Mark up the Grooved side and it will stay on.   I couldnt tell any difference in sensitivity before or after.  On the smooth side it is just like a dry erase marker, it will come right off.  If you want to remove it from the rough side, use a tooth brush and a little soap,  scrub gently with the grain(side to side).  I know this because after blacking it in I wasn't getting the same results.  I removed the ink and still different.  finally figured out very small differences in allignment were afferting the range.  Blacked it in again and paid close attention and got the same results.  

Second, allignment is a lot more critical than I ever suspected to PIR performance.  I have been using 1" square holes and on my last cam went to a 3/4" round hole.  Moving the lens up or down a little makes a big difference in the vertival band it was sencing in.  i.e. with a 1/16" movement up and down, the sensor would go from picking up a hand wave at knee level to head level at a range of about 15 feet.  What I mean is it would see it onetime at knee height and not see it untill you raised you hand to head height or above after moving the lens abit.  

I tried 5 different fresnal lens with the RS sensor.  I needed to mount my lens at 1" from the surface of the element because of my enclosure design.  I ended up settleing on the original RS lens and was getting consistant   triggers at 45'.  It was a little less sensitive at the 1" distance than the 0.65" from the factory but it diddn't reduce the range more than 7 to 8 Feet.  Just a little left to right mis allignment (1/16")made a much bigger difference in sensitivity than the distance did.  At time it wouldn't see me at 20 feet.

I usually use the MS20 and I have always just kinda got them close left to right and up and down).  I have noticed quite a bit of difference in sensitivity between different cameras I have built and always chocked it up to difference in the sensors themselves.  I always get 35 to 40 feet (my target) but some reach out to 70'.  this may explain some of those differences.  
 

Tinhorn

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Excellent work AEH

be nice to camo the white Fresnel Len's a little

I opened up a security system PIR a while back and noticed a Sensitivity Adjustment on it.  It was a hold down screw you loosened and slid the PIR board (with the detector on it) up and down instead of adjusting the distance from the lens (like you described in your post)   The movement allowed by the screw was "Very Little" so a little must go a long way, like you said.

Thanx for the info

Tinhorn
 

TNDEERHUNTER

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Thanks for the info. I have found the same thing in my tests. I wanted to cut down the distance my RS reached to 35' because my flash doesn't reach any further. So I move my lens over 1/16 to 1/4" this gives me about 35'. LOL
 

gantley

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i have 2 cameras at this point.  i have had good luck at tapeing off a 1 inch strip down the middle with masking tape.  then i paint the camera and detector and everythine around me.  this narrows my detection with.  as for as depth, i have not had mucn luck.  i did have my best luck when i placed the camera at a very narrow spot in the trail....  but that is not exactly what you are doing here......
 

Tinhorn

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Thanx for reminding me CF Bob, I snuck a copy of AEH's report over to Random Thoughts .......
 

Shrewshooter

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The only problem i had was that the cam was going off before the animales were even in the picture at about 15 yards.Just the head or nose would show up. I taped off both sides so that i only had about 3.5 of the fresno lens ribbs showing or about 1" wide. Also taped off about 1/8" across the bottom to cut out rabbits and things like that . It works perfect. If i do want ot get all the smaller critters i just aim the cam down a hair when i set it up. Now i get great picks and the distance does not seem to be a problem at all.My flash is good out to atleast 60'. Mike
 

bat

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Tinhorn.....you got me thinking again hmmmmm.....now you know that spells trouble hehe besides being dangerous!  I remember I had an old camo netting face mask somewhere around here.  Found it and spread it across the front of the cam to camo the fresnal lens.......and it still works, don't know how good yet but just might possible be a camo solution to the white part of the fresnal lens, if that is the color you are using "RS". (I know some people get the colored fresnal lens and put them in place of the white one.)  I tried this at about 20' tonight and will try it at a farther distance tomorrow.  The PIR still can see thru the mess in the netting....may have to shift it a little one way or the other to allow it to be centered.  Might can also make a crisscross pattern of some sort of thin colored material that would not completely block off the PIR and glue it in front of the lens.  bat  
 

Handcannon

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Hi guy's, I have been using Createx transparent gray air brush paint to color my fresnels, it helps camo the lense and also seems to help out on the falsies with the ms20s haven't done it on my RS sensors though so don't know about them.  Also my check my post on the other thread about fresnel lens alignment too. Just remember trying different things is most of the fun!
 

bat

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The mesh idea I tried worked....and didn't work.  It worked but it cuts down so the distance to about 15' on my RS, so it would be ok for some situations but not for others.
just my 2¢, bat
 

Tinhorn

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I messed with the mesh idea too, a little.  

I build a "CamBurglar" to try and catch the theves breaking into my sister's cabin.  I thought we mite hide it behind a lace curtain (with the flash off) and did a test.  The MS20 worked across the living room just fine, probably 15 to 20'   I shifted the cam around behind the curtain several times tho and there was a difference in detection range sometimes (a lot less) so Bat is probably right, mite have to adjust the mesh to get the right window.

Never tried it outdoors to check max range, etc.

Tinhorn
 


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