Flood Triggered Automated Camera System (FTACS)

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1. Camera

For the purposes of the FTACS, a digital camera was clearly the best option due to storage convenience, relatively low cost, and feasibility of internal modifications. Due to the nature of the circuitry on the controlling board, a camera with a sliding on/off switch was preferred over a momentary action switch. This requirement limited the options available, but a suitable candidate was easily found – the Panasonic Lumix LS3 (Fig. 4). It features 8MP resolution, and had the added benefit of being simple to disassemble (Fig. 5), which aided the modification process. A 16GB SD card was installed in the camera, which should hold 8000 photos at 5MP resolution.

Figure 4 - The brand new Panasonic Lumix

Figure 5 - The gutted camera

The locations of the on/off switch and AF/Shutter switches were identified, and thin gauge enamel wire was soldered onto the respective copper pads (Fig. 6).

Figure 6- Soldering onto the existing switches

Figure 5 - The box and fan

The camera was mounted in an IP65 rated waterproof enclosure (Fig. 7) with a transparent lid to allow incoming light to the shutter. As the installation site has little protection from solar radiation, it frequently experiences temperatures above 35C. As such, it was necessary to install an 80mm computer fan (rated IP55) inside the box to provide cooling and ventilation.

Ventilation holes were drilled into the back of the housing, along with mounting brackets secured with pop rivets (Fig. 8). An 8 pin DIN socket was also installed on the box (Fig. 9) to allow communication between the camera and the controller board, which was to be external.

Figure 8- Mounting brackets

Figure 9- The box in its semi-completed state

Fig. 10 shows the semi-complete housing with wires from the modified camera connected to the DIN socket. The completed camera box is shown in Fig. 11, with an elastic band merely to hold the two halves in place prior to installation of a waterproofing rubber gasket.

Figure 10 - Mounting the camera inside

Figure 11- The completed camera and box


2. Enclosure

The camera box itself was not deemed satisfactory protection, as the ventilation holes meant that some water ingress would be permitted during heavy rain, and thus the camera would be subject to the elements. With this consideration in mind, a heavy duty enclosure was designed both to reduce the internal temperature and prevent water ingress. This enclosure was developed from a humble looking waste paper bin from Bunnings Warehouse. An opening slot for the camera shutter was cut out of the plastic (Fig. 12), and right angle brackets were fixed at all four corners of the base (Fig. 13).

Figure 12 - A humble waste paper bin

Figure 13- The bin being slaughtered

Brackets were also fixed on both sides of the open slot (Fig. 14) in order to mount a “roof” to further protect against heavy rainfall. The “roof” was constructed using a rectangular slab of 5mm fibre cement and was mounted at a slight slant to prevent water inundation (Fig. 15).

Figure 14 - Stabilisation and roof brackets

Figure 15 - Sloping fibre cement roof

Finally, the entire enclosure was wrapped in reflective aluminium roof foil to protect the plastic enclosure from the damaging effects of UV radiation. This foil was secured in place with heavy duty aluminium tape (Fig. 16).

Figure 16- The completed enclosure


3. Controller Board

The full circuit diagram of the control board is shown in Fig. 17. The board consists (from left to right) of a 555 timer configured to operate at a frequency that will close the shutter every 15 minutes, a J/K flip flop IC which enables/disables the auto-focus (AF), a NOR gate which selects the appropriate time to trigger the shutter, and finally two relays with their respective BC548 driving transistors and protection diodes. This is the same circuit (and board) used in my time lapse photography system.

Figure 17 - Schematic diagram for the controller board

The 555 timer IC is wired in the regular astable mode, with the values of components chosen such that the frequency is close to 1 per 7.5 min (or ~0.0022 Hz). The AF relay is toggled on and off via the flip flop configured in toggle mode which operates on the rising pulse. Some straightforward logic via the NOR gate ensures that the shutter is operated only when the camera is focused – that is, on the falling edge of the clock signal. The associated timing diagram is provided in Fig. 18.

Figure 18- The associated relay activation timing diagram

The completed board was constructed on strip board (Fig. 19) after initial testing on a breadboard was successful. The relays chosen had a maximum contact current rating of 3A, which proved to be huge overkill for the switching of such small signals. As such, they drew a lot more current when operational than would be necessary otherwise. However their relatively low cost was an advantage, and should prove to be fairly robust in the field.

Figure 19 - The completed controller board

Figure 20 - Voltage regulator slave board

The voltage regulator supplies 5.1V to the camera DC input, thereby bypassing the camera’s internal battery but at the same time keeping it charged so that the date and time settings inside the camera would be preserved. This was constructed using an LD1117V low dropout regulator; although a standard LM317 variable voltage regulator would have sufficed. This part of the circuit was also constructed on strip board (Fig. 20).

Circuitry for the water sensor was mounted on the same board as the two circuits above (Fig. 21). This was built from a modified “kit”; the design consists simply of two water probes which trigger a DPDT relay via a Darlington transistor. The rest of the circuitry on the board is wired through this relay such that no components will be powered when the ground is dry.

Figure 21 - Completed board with water sensor unit

Figure 22 - Battery to be used in the field

Power for the FTACS is sourced from a 12V, 17.2Ah battery (Fig. 22). The 9V battery is for an indication of scale only, and is not present in the final installation.


4. Water probes

A crucial element of the FTACS involves the actual sensing of the water level itself. In essence, the entire system needs to be switched on only when the water level rises above ground. To do this, the circuitry described previously was employed. The probes itself, however, need to be mounted at ground level rather than at the observation box (which is about 6m above ground level) with the other components of the system.
The probes themselves were constructed out of two stainless steel rivets which were each secured in a watertight cable grommet and connected to a naked strip terminal at the other end (Fig. 23). These grommets were then mounted in an IP65 rated ABS box, and connected to a 15m length of twin-core power cable (Fig. 24).

Figure 23 - SS rivets used as water probes

Figure 24 - The water probe box with lid off

The cable was threaded through a third cable grommet and waterproofed by adding a couple of layers of heat shrink tubing (Fig. 25). The probe box was completed after inserting the waterproofing rubber gasket. The completed probe box (Fig. 26) is capable of withstanding long term submersion underwater.

Figure 25 - Watertight cable relief

Figure 26 - Completed water probe box



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