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The benefits of using solar tracking mechanisms, particularly where photovoltaic arrays are used to power a water pumping system, are discussed. The principles of designing and constructing a simple automatic solar tracking mechanism are shown. A single-axis tracking system is used, involving the rotation of the solar receiver at the rate of 15 deg per hour around a north-south axis. A water clock device, with a system of valves controlling the flow of water and so the tracking and reversing rotation mode, is used to track the sun. One hundred and forty to 320 litres of water were used in each cycle. The results of the tests shown that the maximum error of tracking was 15 deg during a 4-week period. After that period, resetting of the mechanism was necessary. The total cost of the materials used for construction of the tracking mechanism was approximately US$50, excluding the frame supporting the photovoltaic array.