Modifying a Pencam for Rocket Launch Triggered Aerial Movies.

When I first got interested in water rockets, the most fascinating images I saw on the Internet were the movies of rocket launches. The best of these by far were the onboard, in-flight movies. This got me into thinking about how this could be done. The camera needed to be light, have a sensible amount of memory, be able to take a reasonable length of movie and be cheap. The answer came with the a surf on www.ebay.co.uk. I did a search for "pencam" and found the camera featured here. It can take stills, 10 seconds worth of movies at 640x480 resolution (10 frames per second) or 30+ seconds worth of movies at 320x240 resolution (again at 10 fps). It has 64Meg of SDRAM. The only problem I had was how to trigger the camera to take a movie without setting it up while stood next to a pressurised rocket (not sensible).
After some faffing about I figured a way of triggering it using the launch string and of all things a paper clip. It does mean a small modification to the camera itself, fitting two new switches to the side of the camera. Needless to say this modification will void any warranty the camera might have had.

How the camera is triggered.

This camera has two buttons, one on the back the other on the top. The one on the back is used to turn the camera on or off and to select options, the one on the top is the shutter and also used to confirm options. To take a movie, after selecting the right option,  the top button (shutter) needs to be held down for the duration of the movie.
The camera will also switch itself off after 1 minute idle time.
I found that if the camera is set to movie mode then switched off, if you then hold down the shutter and switch the camera on by holding the back button down, the camera will
a.) Not turn itself off while both buttons are held down and
b.) it will begin to take a movie when only the back button is released.

Now I had a way of remotely triggering the camera I needed new switches.
These came from Maplin (www.maplin.co.uk)
An ultra miniature SPST toggle switch (code: FH97F) and
a Sub-Microswitch/lever (code: GW67X)
Also needed are some short lengths of fine wire, solder, a soldering iron and a set of jewelers screwdrivers.

Opening the camera up

Pull the battery compartment lid out and underneath you will see a small screw. Remove this screw to release the front cover of the camera. Carefully remove the front cover, there are plastic clips about one third of the way from the top of the camera and one at the top (just visible in the next image). Try not to break these as you remove the cover.

The camera case is in three parts, the front cover, the side section and the rear cover.

This is a view of the camera with the front cover removed.

You now need to remove the battery compartment and side section of the camera case (all one unit).

Remove the two screws arrowed to release the battery compartment and side section.

Be very careful about the wires from the battery comparment to the circuit board, these will very easily break off if put under any slight stress. (they can be soldered back on if this happens)

With the side section removed, you now need to remove the circuit board. The board is held down by the screws arrowed. Removing this board will also expose the CMOS sensor, take care not to get dirt on the sensor and also some of the circuitry is static sensitive, an anti static wristband would be ideal, however I didn't bother and the camera still works OK. I did however minimise how much contact I made with the circuit board.

Soldering in the new switches

When you remove the circuit board, the LCD display may become detached, don't worry about this, it is held in contact by being squeezed between the rear panel and the circuit board and some conductive foam rubber strips. Make sure you know which way up it goes and carefully slot it into the back panel, with the foam rubber strips in place.

Turn the board over.
Arrowed in the picture are the connections from the cameras rear switch to the micro switch. Strip and tin the ends of your wire and cut the conductor to length (2-3mm) beyond the insulation. Hold the wire on the point you are soldering to and apply only as much heat as is necessary to melt the solder. Remove the heat and allow the solder to cool before letting go of the wire.

 At the micro switch...

I drilled 3 small holes in the side right hand side of the side panel of the casing to accept the switch contacts for me to solder to. I then glued the micro switch to the panel using hot melt glue, with the contacts poking through these holes.
I then soldered the wires from the switch on the circuit board to the "make" contacts of the micro switch.
i.e. pressing the lever makes a contact.

This switch is used to trigger the movie at launch by removing a paper clip paper clip.

 With the circuit board the turned back the right way, connect the camera's top switch (shutter) to the toggle switch. This switch I fixed to the left side if the side panel. Be very careful where you drill the hole for this toggle switch as it is a very tight fit next to the camera lens housing, when everything is put back together. I had to gently bend the terminals slightly out of the way to make the switch fit in place.
Again solder to the points on the circuit board arrowed and connect to the switch

 Here are the two switches soldered up and ready to close the case up again,

Closing the camera up again

Again the side panel and the circuit board are in place and screwed down. Make sure the circuit board is screwed down properly, otherwise you might find that the LCD display, doesn't display properly.

You will notice if you look carefully, I have forgotten to put the top shutter button back in place, I did this every time I closed the case (arrgh!) It is in place in the next picture.

Make sure everything is where it should be before putting the front cover back on - including the battery compartment cover, view finder, etc, etc.

Here it is, the finished product ready for attaching to a rocket (oo-er)

I recommend taping up the battery compartment and case with electrical tape. Any loss of power to the camera will wipe the memory. I found this out the hard way, after an unplanned balistic flight the batteries were jolted out of the camera, never to be seen again.

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