Mark II Underwater Video Housing - construction details

I've had a lot of requests for more details on how to build either the housing or the electronics so here are some further details.

Click here for a set of scale drawings. These are full size and can be printed out on multiple sheets and stuck together.

First the electronics - which most people seem to be unsure about. If you look at the picture on the left you can clearly see the controller on the inside of the housing.

At the top are two reed switches which operate the camera zoom in and out - they are thin glass tubes that have contacts which close when in proximity to a magnet. They are connected to the blue connector (so I can disconnect everything easily). The blue connector is glued onto the back of the printed circuit board of the remote control that came with the camera. To the left of the PCB is a black battery box which has two AA bateries to provide the 1.5 volts needed for the remote.

The wires that come out of the blue connector go through the PCB and are attached to the other side. If you look at the top picture again you will see that the reed witches are joined in the middle (blue wire) and have a black wire at each end. These correspond to the same coloured wires on the PCB (the other wires here are for other functions on the camera - ignore them). These are attached to the PCB by removing some of the coating on the tracks on the PCB and soldering onto them. The tracks are not broken. When the reed switch closes, when a magnet passes over it, the wires short out the button and that operates the zoom in or out, as if someone had pressed the button on the remote. Simple.
On the outside of the housing are sliders which have powerful magnets in them. As they are moved backwards or forwards they pass over the reed switches on the inside of the housing and cause them to close. This is how the camera is controlled without drilling any holes in the housing. No holes means less chance of a leak.

The handle below the slider is made from a piece of the original tube (you can see the curve) with a piece of plumbing pipe glued to the bottom of it for the handle. This assembly is screwed to the housing (not all the way through) so it can be removed for transit etc.

The camera record on/off is controlled seperately because when the camera goes to sleep it cannot be woken up by the remote. However pushing the record button on the camera does wake it up so I have used a solenoid to press the button for me. The solenoid is a 12 volt unit running from two 9v batteries in series (18volts - but that's fine as it's very short duration and the batteries supply limited current). This uses another reed switch which supplies power from the batteries to the solenoid instead of being connected to the remote. The picture left shows the setup and you can also see the mounting screws for the camera which fit the tripod mount.
The plate that the camera mounts on slides in and out of the housing in the grooves shown left. The screw in the foreground is a stop for the camera mounting plates and also fits into the lead (shown underneath the bottom shelf) to stop it moving about.
This is a picture of the end plate retaining clips showing the position they are in when open. Note the amount of X ring squish between the end plate and the housing and the position of the clip prior to closing. This is about the optimum angle for a nice tight fit without overloading the clip. If you remove the X ring (or O ring) the clips should still be tight enough to hold the end plate on. If they are not tight enough they can come undone underwater when under pressure. If this happens and you don't notice, the end will fall off at the surface when the pressure has gone.
This is another picture of the end plate retaining clip. The holes are tapped into the plastic - be careful or it will crack. Note the small screw to the left. This is screwed in from the other side and along with two others at 120 degree separation, assists with alignment of the end plates when they are attached.
Here is a shot of the X ring groove. You can also see the lead ballast, a retaining clip and the bottom of the camera remote control, top left. If I was building another one (and I have) I would use standard O rings instead of the X rings. They are much cheaper and the groove tolerences are much easier to work with.

Take a look a the Mark III to see what I mean.


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