Flood Triggered Automated Camera System (FTACS)
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Construction
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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