Possum TV Cameras


There are many types of security camera available these days, but there are certain special requirements for a possum (or other wildlife) box camera which you need to consider:



One thing I would also recommend is to be sceptical of advice from people who haven't actually set up a nestbox camera, even if they are otherwise knowledgeable. I once talked to a professional camera installer who worked for OzSpy, and he said that cameras like the ones we have used are no good because moisture condenses inside them, causing them to fail after a few months. While I would be willing to accept that this might be the case for cameras which are left turned off for long periods, the fact is that possum box cameras are kept running continuously and the heat they generate prevents condensation from occurring. Our oldest camera has been running for nearly 8 years and is still working.


We have not yet located the ideal camera, but currently we use the following two types, which have shown themselves to be quite usable.




Swann Day-and-Night Camera Swann Day-and-Night

The first two boxes installed had this type of camera. This is a very easy camera to use; nothing to configure and no extra hardware needed (except that you'll probably need an extension cable, but Swann sell a matching extension cable as well). Unfortunately, Swann seem to have stopped making this camera, so a detailed discussion of its pros and cons is a bit pointless. For the record, this camera had the following specs:



If you can still find one of these cameras anywhere, by all means get it. The image is marginally worse than the other camera we use and the narrow lens angle means you have to aim it carefully for the best picture, but otherwise it's almost ideal for the application and runs much cooler than a CCD camera.




QC3474 CameraJaycar/Electus QC3474

This is the new "standard" camera that I've installed in boxes 3 to 7. It's relatively low cost and it does pretty much everything that's needed of it. Disadvantages are that you need to build a separate infra-red illuminator (described below), it runs a little hot, and the mounting screws don't hold it very securely, so it's vulnerable to being knocked out of alignment by inquisitive possums. The specs of this camera are as follows:



The short stub of cable supplied with the camera has a couple of advantages. Firstly it allows you to disconnect the camera easily if you're taking the box out of the tree. Secondly, it allows you to hook in a hand-held video monitor, so you can re-align the camera more easily if it gets knocked out of position.




QC3473 CameraJaycar QC3473 "pinhole" camera

This is very similar to the QC3474. The main differences being that it's smaller and has a "pinhole" lens. It's not actually a true pinhole camera, but merely has a very small lens. The specs are:



When the original Box 2 camera reached the end of its life, this camera was chosen as a replacement, mainly because box 2 is very small and cramped and possums often get very close to camera. This means that the camera needs a very large depth of field to keep the possum in focus. Supposedly, the smaller the aperture of a camera lens, the greater the depth of field, so I had hoped that the particularly tiny lens on this camera would be ideal. In practice, however, it didn't seem to make that much difference - if anything it was maginally worse.


This camera currently seems to be out of stock at Jaycar, but otherwise is probably worth considering if you need a very small camera to install in a restricted location.




Infra-red Illuminator
 

An IR illuminator can be made from a cluster of IR LEDs. There are two main types of IR LED available; those with a "short" wavelength of around 850 nm, which emit a dull red glow, and those with a "long" wavelength of around 940 nm, which are invisible to the naked eye. Unfortunately, cameras are 3-4 times more sensitive to the former type, and therefore illuminators designed for use with (or incorporated into) day-night cameras generally use this type of LED. The Swann day-night camera was an exception to this rule.


For a possum box, you need the "long" wavelength type; you don't want a red glow that might scare away possums and it doesn't matter that it's less powerful since you only have to illuminate the inside of a small box rather than a room or yard.


I have been unable to find a commercially made IR illuminator which is suitable for a possum box. All of them are far too powerful, and virtually all use the "short" wavelength LEDs as well. Fortunately, it's quite easy to make an IR illuminator. The simplest way is to connect a string of around six IR LEDs in series with an appropriately sized resistor, however I decided to use an LM317 voltage regulator as a constant current source to ensure the LEDs would always run at the selected current, regardless of supply voltage variations.


This is the schematic of the circuit I used.


Jaycar is a good source for components, and you can also try looking at Radio Spares or Element 14 (formerly Farnell). These last two are notoriously expensive (some items have outrageous markups), but the pricing varies a lot and you can often find stuff cheaper than at your local Jaycar store. Also, they've got a much larger range of gear available and (unlike some online stores) do have stuff in stock when they say they do, and deliver extremely promptly. eBay is also a possibility if you're very careful.




Cabling

Most of the difficulties and annoyances related to installing a possum box camera are caused by the need to bring a cable back from the camera. Cables run outside get subject to so much wear and tear that even if they are rated for exterior use (e.g. UV stabilised etc.), it's still better to run them inside electrical conduit.


I ran virtually all of the exterior cables inside 25 mm PVC electrical conduit. I initially used 20 mm conduit, but this is really too small to coax the cables through, especially if you've already terminated them (BNC connectors are really fat). If you are running cabling to more than a couple of cameras, you need to go up to 32 mm conduit. I'd also recommend you limit the amount of flexible conduit that you use; the ridges on this stuff make it really difficult to get cables through and the longer the section, the worse it is.


You'll find that in addition to conduit, you'll also require a surprising quantity of miscellaneous fittings (elbows, saddles, junction boxes etc.) to make a good installation, but it's worth the time to do it properly. It's usually best to buy this sort of stuff from your local electrical supplier (e.g. Ideal Electrical or Haymans, if you're in Australia) rather than a normal hardware store because they've generally got lower prices and a better range. A few quick comments:



Don't be shy about purchasing stuff from an electrical supplier if you're not a registered electrician. There are no laws that say they can't sell this stuff to members of the public, and you'll generally find them to be helpful and co-operative.


You can buy pre-made cables with all the right connectors already fitted. These are OK to start with (I used them on the first two cameras) and handy to have available for temporary hookups, but with a larger installation, it's best to cut your own cables to size and terminate them yourself. I have generally used 0.5 mm2 speaker cable for power, RG-59 coax for the video and cheap shielded audio cable for the audio. Power and audio cables are terminated by simply soldering on an appropriate connector, however the coax is best terminated with a crimp-on connector, and this means purchasing the correctly sized crimping tool.


It is possible to use RG-6 coax in place of RG-59. There are bitter arguments about the merits of each type on the web; generally, both will work, but RG-59 is usually both cheaper and somewhat more suited to video cameras.