Thermostat Controlled Trail Cam

Richard Webb

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After getting 24 blank pic's during 101 -104 degree temperatures I knew that something had to be done.  Later, while tinkering I found that if you don't keep the daylight sensor powered it wont be fast enough since it is two parallel operations, (1 to trigger the camera and one to not trigger if daylight). So, to eliminate the possible racing condition something has to be using battery current all the time even if a timer is used.  This led me to a typical Furnace Thermostat, because the sealed mercury switch is mechanical not electrical, which means absolutely no battery current is used. I selected the LUX model T10-1141 up at the local hardware store. Cost is $9.99, and the anticipator has a slip clutch. That means that if the trail cam isn't perfectly level in the field a last minute adjustment can be made with the slip clutch. The thermostat simply breaks contact with the shutter wires at temperatures above the thermostat setting, and at all temperatures below the thermostat setting makes contact with the shutter wires. On the down side, a shot of WD-40 will be needed on the spring to stop rust.



 

The picture above shows that the trail cam wont take a picture, because of high temperature.  The RS 49-425 seems to work best at where I have it set (75 degrees & below), but the MS20 will probably do okay at a higher setting.  Next, will try to shut off the PIR battery, because the mercury switch doesn't need power to get going again.



(Edited by Richard Webb at 6:49 am on June 30, 2001)
 



Archilochus

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Hi Richard,
I've been thinking about the temperature issue.
It occurs to me that high temps alone should not be a problem, as the PIR element sensitivity falls as background and subject temps approach equality.  It seems to me the problem must be related to background temperature changing fast enough for the detector to be fooled.  This could be caused by a heated area of ground having a sudden breeze cool it off, or even a heavy shadow passing in front of the sensor from a passing cloud or wind tossed leafy branch.
I've noticed almost all of my pictures of nothing have some distinct sunny areas and some distinct shaded areas.  I never kept track of information such as if the day was windy - but I'm guessing the shaded areas in those pics were being moved around by wind.  I've had this kind of false triggering even on sunny winter days.
I've started placing my cams in areas sheltered from sun
*and* wind and have noticed a distinct reduction in false triggerings - even when temps are in the 90's.
If you have more than one cam working at the moment, maybe you could try an experiment.  Wait for conditions similar to the day you got the bad pics - put one cam in the same place and put another in a shaded, wind-sheltered spot and see if there is any difference.
Do you ever get really hot nights out there?  If so, it would be interesting to put the cam out on a very hot *night* and see if there are any false triggerings during the night.

>>>>>>
I think that if you cut the battery power to either the 49-425 or the MS-20 and then re-apply power with the camera itself turned on, either sensor will cause the cam shutter to close.

Archilochus
 

Richard Webb

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Hi Arch - Thanks for the tips on camera placement.  I could probably save myself a lot of trouble by simply putting out the cameras in the right places. We have a sea breeze in this area at about 3 PM, and it cools down quickly. The terrain is hilly oak savanna to woodsy ravines with patches of chaparral.  When it's hot the wind blows pockets of hot air around. I decided for the thermostat rather than a wind speed sensor, because I got 14 blank frames between 11AM & 3PM on June 10th when the temperature was up over 100 degrees. Another plus for the thermostat was that the weather report gives the predicted night temperatures, so a thermostat can be set for night use only. All this is strictly experimental, and having fun doing it.
 

Jaggermax

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Well, i just finished my new microcontroller based cam just this week.  I hopefully will be posting pictures of it as soon as I can.  I read many tech sheets for the PIRs out there and I took an automated approach to overcome this high temperature stability issue.

I built in a digital temperature sensor that constantly monitors the outside temperature.  When the temperature gets above 97 degrees, I turn off the PIR sensor to eliminate false triggers.  So far, it works well.  I live in south Mississippi and it has been about 90 to 95 degrees.  The camera still detects fine at that temp, but at 97 degrees, (I held a blow drier near the PIR to test it,) and once the housing was heated well, it started taking pictures one after another.  
 

Archilochus

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Hi Richard, Jaggermax,

Richard....A wind speed sensor... Now there's an idea!!
>>>>>>>
Anyway....What I meant was that something with a higher or lower temperature than the background must be  *moving*  by the sensor in order for the sensor to be triggered.  False triggerings due to hot/cool air pockets or moving shadow/sunnny spots can fool the sensor at  *any*  temperature.  Since I never get empty pics at night (even windy nights in the high 80's), I figure that the falsing is due to changing lighting conditions rather than temperature.
Since you have higher temps out West, you'll be able to test this theory by putting your cams out on very hot/windy *nights* and see what happens.  I'm guessing that even on very hot/windy nights that you don't get false triggers of the sensor.
>>>>>>>>>
Are you putting the thermostat (or, for Jaggermax, the temp sensor)  inside   the housing?  If so, It might take quite a while for the temperature inside the box to equalize with the outside temp.  If the thermostat is inside the box you might still get the falsing during the time the interior temp is still lower than the exterior temp.
>>>>>>>>>
Here's another fun problem.... When there is a cool rain on a warm night, the cool rainwater running down the lens of the PIR sensor can cause false triggerings also.  I think some people have been using hoods over their PIR lenses to reduce this problem.  I try to position my cameras so that they tilt down a bit, this seems to reduce or nearly eliminate the rainwater triggering.
>>>>>>>

Hi Jaggermax... When you did the hair dryer test, was any of the heated air blowing across the front of the sensor?  If so, the moving, heated air could have caused your false triggering.  I've read that heating/cooling systems are a real problem for security system PIR sensors as the heat / AC coming on starts the heated/cooled air moving and trips the sensors.  I can't wait to see the results with your cam.  I'd love to have more knowledge about writing code for these micro-processors, but the books are just too damn big!!  Seems that a micro is the easiest way to build the circuits for a trail-cam, if you know how to write the code.
>>>>>>>

Anyone used something like "Rain-ex" to help keep the camera lens window clear in the rain??  I was wondering if it works.  Hate seeing what would be a nice pic ruined with a big streak of rainwater across the lens.

Archilochus
 

Richard Webb

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Hi guys - Yesterday I set out my thermostat controlled cam at the reservoir where I got my first pics. After a few days we'll see what happens. Today we are having a ham radio flea market, and many hams have a mini weather station setup. These guys give a weather report when they first start talking, so there should be some old weather junk for sale. I'm looking for Slow Scan Television equipment for my next trail cam project, but will also keep an eye for wind sensors. Wish I knew more about micro controllers, because there is usually tons of that stuff at the swap meet.  
 

Richard Webb

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Hi guys - I checked the cam today, and it didn't take a picture all week.  So, I moved the thermostat up from 70 degrees to 80 degrees.  We'll see what happens in a couple of weeks. While we were out on the lake we noticed that there were 3 seperate families of doe & fawns in the shade under oak trees. Typical black tails.

Ammended:

I found one night picture on the roll that was in the thermostat controlled cam, so the project is on target.  



(Edited by Richard Webb at 8:45 pm on July 6, 2001)
 

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