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Friday, 13 July 2012

Ltl Acorn 6210 HD Series trail camera re-design cures water problem.

Fig 1:   Ltl Acorn 6210MMX

Most of you reading this will be aware of the huge disappointment felt, when the recent modifications to this camera failed to completely eliminate the water ingress. There was a reduction, but the basic problem persisted.

I had been testing the new unit for a week and although there was less water entering the camera, and non was actually getting into the control panel, condensation was still occurring. I was determined to find the reason for this.

The factory re-design of the control panel housing was certainly working, because although, during tests, there was water in the camera, it was not affecting this area. It was however, collecting at the back above the hinge assembly, and was saturating the inside of the case. I decided to go back to basics and re-analyse the whole process.

The strangest thing about this issue, was that the manufacturers had told me, I was the only person reporting this problem to them; and yet many, many people in the UK were having this problem. It occurred to me that if this were true, then maybe the cause related to particular environmental or climatic conditions.

Fig 2:  Oceanic climate areas
These are the areas of the world where the type of
problem discussed in the text, is most likely to occur.
I already had an idea that case temperature variations may have something to do with it because of a similar issue with a Bushnell with a bad case seal. While pondering this, I had a eureka moment, which went something like, humidity, volume of air, temperature change, expansion and contraction, evaporation and condensation.

So what was likely to cause this problem to predominate in the UK?

I did some research into climate areas and realised that western Europe and particularly the UK, are the largest region of Oceanic (Western Maritime) climate (Figure 2 - Oceanic climate areas coloured green) in the world. Scotland also has areas with subpolar oceanic climates. In these climate types, heavy, cold rain onto relatively warm surfaces is a feature which provides exactly the right conditions for this problem to occur.
Fig 3:   Changes to door panel
showing the extra sinking below the hinge,
and the cut down sides for drainage.

Testing by the manufacturers did not reveal this problem because they are in a tropical climate where wide temperature fluctuations don't normally occur. Even with heavy rainfall, air and rainwater temperatures are similar and relatively constant.

Tests here in Scotland, showed that in ambient conditions where the air temperature in shade was 17C, and in sun was 25C, the cameras case temperature in direct sunlight would rise to 30C. In changeable weather conditions, a sudden rainfall, even in June, would cause the case temperature to drop rapidly by at least 10C. This in turn, would  
Fig 4:   Enlarged water sink below hinge
cause the cameras internal air mass to contract, thereby producing a vacuum.

The old case had a weakness in the seal, at each end of the hinge and also, because of the hinge assembly position and design, water would collect around it during rainfall. Any suction from the vacuum would pull this water inside the case, which would then collect around the control panel.

This seal weakness had already been recognised and in the new case design, the hinge had improved water protection and sinking. Instead of sitting in the base of the door, the control panel
Fig 5:   Side view of modified door
was now raised above it with a 4 mm skirt completely surrounding it, and a tolerance fit with the control panel housing. This was very effective and the reason why initial water ingress was not entering the control panel as it had previously.

Fig 6:   Front view of modified door.
The ends have now been removed completely.
See figure 7 below.
Water was however, still entering the case, and in sufficient quantity to eventually, still cause a problem. I had previously voiced my opinion that the bottom door did not require a seal because, as it was, the case interior was unable to equalise with changing ambient conditions. I felt that with an improved door/control panel design, the seal could be eliminated, thereby allowing the case to breath.

In an attempt to prove my theory, I took the new test camera to the work bench and made some changes, as illustrated in figures 3 to 6.

I removed the door seal, cut extra sinking below the hinge assembly and provided drainage at the sides. I then re-assembled the camera, and started testing again.

The modified camera has been tested for over a week in both natural and artificial rainfall; and there is no indication of water and condensation collecting inside the case The only condensation effect you may see is
Fig 7:   Control panel door edge.
water in the LED array. This occurs during high humidity, when the sun heats the case sufficiently to cause internal evaporation. When the case cools again, water condenses in the top of the case, including inside the array window. This quickly disperses as case temperature and humidity equalise with the outside conditions, allowed by the removal of the door seal. It has no effect on the camera's circuits or the operation of the LED array, as they are designed to operate through 5 to 95% humidity.
Fig 8:   Underside of door.
Because of the equalised environment in and around the case, the only way the control panel will suffer from water is if you drop it in a river.
Even then, providing it is dried thoroughly before use, there will be no lasting damage.

Figures 7 to 9 show the hand made, pre-production shell, with the latest modifications. The door panel profile is now inside the case, the seal is removed, and there's plenty of extra sinking around the hinge assembly.

The combination of the raised control panel and its interference fit with the door's raised internal flange, will prevent any water entering the control panel.
Fig 9:  Control panel housing.
The absence of the seal, extra drainage and sinking will allow water to freely run off the case, and not be drawn inside.

The new mould is being made and I am told that the fully modified camera will be available by the last week in July 2012.

The Ltl Acorn 6210 HD Series cameras are very high specification cameras and these last modifications should make them a reliable, high performer, in most professional user environments.
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This web site is about the wildlife, particularly the mammals, of the Glen Affric National Nature Reserve area in the north west Highlands of Scotland, UK; and the equipment I use to search for them, which is chiefly trail cameras.

I provide a technical support and parts service for the Ltl Acorn range of cameras and the income from this provides for the upkeep of this site and the purchase of cameras for my own surveying.

I hope you find the site useful and informative; and please contact me if you have any questions that I haven't already covered.