After a few experiments I have a pretty decent platform for capturing long term time lapse footage. The system is designed to run for around a month and captures a photo every thirty seconds during daylight hours. It's a fairly cheap build so I'm not too worried about theft or accidental damage. This post contains build instructions and sample code to get the camera up and running. Before that, here's a quick video made from a few test runs:
On the hardware side you need an Arduino Mega 2560 REV3, the OV5642 camera module, an SD module and card, a battery and a solar panel. You'll also want a waterproof case, cables and some zip ties. Everything I used is on this Amazon list. I tried a few different power solutions and the Voltaic Systems 6W solar panel + 6,400 mAh battery combination is ideal. Their battery banks are 'always on' and continue to provide power even when the Arduino isn't doing anything. Most battery banks shut down when there is low power usage. In my testing the 6W panel managed to keep the system running with no issues.
The main limitation is that Arduino only supports up to 32GB SD cards. With the code below this allows around a month of photos. Depending on the application you could go much longer - the variables are interval (I'm shooting a frame around every 30 seconds) and file size (lower resolution and/or JPEG quality). At some point I'd like to figure out cellular upload but for now 32GB will have to do.
Assembly is pretty easy. The OV5642 camera uses both the I2C and SPI buses. For I2C connect the pins labeled SCL and SDA to SCL and SDA on the Arduino Mega (D21 and D20 pins - search Arduino Mega pinout if necessary). The SPI connections are MISO, MOSI and SCK (available at D50, D51 and D52). You also need CS (chip select) - wire this to D10. Finally wire ground and power to the GND and 5V pins. The SD module also uses SPI. Wire its MISO, MOSI and SCK to the same pins (D50, D51 and D52). SD needs a separate CS (chip select), use D7. And finally for SD connect ground and power to GND and 5V. That's it.
The box linked above is large enough to fit all the components easily. You'll need to drill two holes, one for the camera lens and one for the solar panel cable. Once assembled, seal around both as well as you can.
To program the Mega you need to install the Arduino IDE and then download and install the ArduCAM library. Make sure that the ArduCAM folder is directly under the libraries folder for your Arduino IDE (on Windows this is probably C:\Program Files (x86)\Arduino\libraries\ArduCAM). Then open the file memorysaver.h in the ArduCAM folder and make sure that only the OV5642 line is uncommented (#define OV5642_MINI_5MP_PLUS). If you get build errors it's almost certainly this step that is the problem so check carefully.
At this point I'd suggest trying the blink sample to make sure that you can connect to and program your board successfully. Once this is working create a new sketch and then copy the code below:
A few notes on the code. Near the top you can uncomment the line #define USE_SERIAL to get diagnostic messages written to the serial monitor. This can be useful for debugging if necessary. The sketch uses the built in LED to indicate problems as well - if everything is working you'll see the LED light up during setup and then switch off once the main loop starts. When a picture is written to the SD card the SD module LED will light up, so if you see that happening every 30 seconds or so then you should be in good shape. If the setup code fails to find the camera or SD module the internal LED will blink indicating that you need to fix something. Check that the OV5642 and SD modules are correctly wired. I would also try disconnecting power from the Mega for a few seconds. I have experienced connection issues with the OV5642 that are only fixed by a power cycle.
At startup there is also a check for existing files on the SD card and the file number is incremented by 1000 as needed until existing files will not be overwritten. This is useful in case the system loses power and restarts for any reason. I have included most configurable parameters for the camera module in the setup code like contrast and exposure adjustments so these should be easy to tweak based on your specific application.
Finally the startup code disables Mega features that are not used and after each photo the camera is powered down and the Mega put to sleep. Each sleep is around nine seconds. The number of sleeps depends on the size of the image - if below 200K it will sleep for around half an hour before trying again. This saves filling up the SD card with nighttime images and preserves power when the solar panel is unlikely to be helpful. This is another area to tweak depending on how you plan to use the system.
If you have any questions (or if you build this and it works for you) please leave a comment below.