Author：Chang Yuan-Tsung, Li Chien, Tainan District Agricultural Research and Extension Station, Council of Agriculture, Executive Yuan

Phalaenopsis is an important floral product in Taiwan for export. An orchid garden is usually over 10,000 square meters in size, in which various types of watering devices are developed with the hope to save manpower. Most automatic watering devices used to be of the suspension type, which does not hinder the movement of operators working under the watering devices and is not restricted by the specifications of the benches. The disadvantage, however, is that the devices work on the fixed benches only and cannot be moved freely. It is not cost effective as orchid needs watering only once in every 7 to 10 days. The new self-propelled watering device, either of the single-lever or the crossover type, moves along different pathways between benches, so one watering device can serve the needs of the whole greenhouse. A moveable coil is used at the water outlet to match the different pot sizes and water the plants from above. As the position of the orchid pots often changes due to their growth and management needs, manual adjustment is needed to ensure the water outlet is at the correct direction to provide even amount of watering. This is why this system is called semi-automatic. It means more labor consumption and continuous water discharge that causes waste of water.

In order to reduce the workload of the watering device operator and solve the problems of waste and uneven watering, Tainan District Agricultural Research and Extension Station improved the watering device so that it can automatically locate the plant for watering. In the laboratory test, the photosensitive element camera is used to locate the coloring point (the plant), and signals are transmitted to the microcomputer control panel to control the water outlet. As the precision design of the mobile water outlet involves higher cost and the risk of malfunctioning, the array-based one-way water discharge valve is used instead, and a laser scanner (single dimension) is installed next to the valve. Four valves work in a group, which uses the data from the laser reflection to determine through algorithms the position of the potted plants for watering. This means that water is discharged only when there are plants below. Fully automatic operation is achieved as there is no need for manual adjustment of the water directions.