This paper describes the design of a robot for cleaning rubbish floating on the water surface. Three important issues for designing the aquatic robots are a cost-effective solution along with robustness and durability. Due to the nature of the cleaning work, we designed the vehicle structure that can provide high stability, good ability in maneuver and can easily collect all the waste flowing in between. A pontoon shaped hull works best for this case and fulfils all the hydrostatic, structural stability criteria. For removal and collection of surface waste, a motor-driven collecting-arm system has been designed for collecting the wastes and redeploying it into a rectangular basket on the hull. This design provides simple and effective waste removal and accommodates large amounts of waste within a small space. For the prototype, the hulls were made up of styrofoam which is wrapped by fibre and then coated with waterproof and resin. It supported together by aluminum. This light and tough structure support the total weight of the system. The propulsion system based on a differential drive mechanism has been designed, which allows the robots to take a 360 turn on the spot and provides high thrust. Electronic circuit and motors have been placing inside the hull, in order to protect them from water. The robot is manually controlled by remote control based on Xbee Pro wireless modules. The testing of the robot prototype proved to be effective in waste collecting and removal. The maximum trash loads that robot can bear is up 16 kg.

Abstrak  Penelitian ini bertujuan untuk merancang instrumen pengukuran panjang fokus lensa bikonveks secara otomatis. Dengan menerapkan sifat lensa bikonveks dimana berkas-berkas sinar  yang paralel terhadap sumbu lensa akan dibiaskan dan berpotongan pada titik fokus. Titik fokus lensa ditentukan menggunakan sensor TEMT6000 dan panjang fokusnya diukur meggunakan motor stepper. Sinar dari dua buah laser dioda yang dipasang sejajar terhadap sumbu lensa akan berpotongan pada titik fokus sehingga intensitas di titik tersebut akan maksimum. Sensor TEMT6000 yang terhubung dengan motor stepper bergerak linier sesumbu dengan sumbu lensa dan berhenti pada titik fokus lensa karena hasil pembacaan sensor bernilai maksimum pada titik tersebut. Mikrokontroler akan menghitung jarak yang ditempuh sensor dan menampilkannya pada display sebagai panjang fokus lensa. Instrumen ini akan diujicobakan pada tiga buah lensa yang memiliki spesifikasi panjang fokus 100 mm, 150 mm, 200 mm, 250 mm dan 300 mm. Berdasarkan penelitian yang dilakukan, panjang fokus hasil pengukuran secara otomatis adalah: 103,8 mm untuk lensa berspesifikasi panjang fokus 100 mm dengan tingkat kesalahan 3,8%, 153,1 mm untuk lensa berspesifikasi panjang fokus 150 mm dengan tingkat kesalahan 2,1%, 203,2 mm untuk lensa berspesifikasi panjang fokus 200 mm dengan tingkat kesalahan 1,6%, 253,2 mm untuk lensa berspesifikasi panjang fokus 250 mm dengan tingkat kesalahan 1,3%, 303,5 mm untuk lensa berspesifikasi panjang fokus 300 mm dengan tingkat kesalahan 1,1%. Penyebab terjadinya penyimpangan titik fokus adalah berkas sinar yang berasal dari laser tidak sejajar dengan sumbu lensa dikarenakan terjadi penyimpangan sudut tembak laser. Kata Kunci: panjang fokus lensa bikonveks, sensor TEMT6000, motor stepper   Abstract This study aims to design an automatic instrument for measuring the focal length of biconvex lens. By applying the property of a biconvex lens, the rays parralel to the axis of the lens will be refracted and intersect at the focal point. The focal point of the lens was determined using a TEMT6000 sensor and the focal length  measured using a stepper motor. The rays from the two laser diodes that were placed parallel to the lens axis would intersect at the focal point so that the intensity at that point would be maximum. TEMT6000 sensor which is connected to the stepper motor moves linearly about the lens axis and stops at the focal point of the lens because the sensor reading is maximum at that point. Microcontroller would calculate the distance travelled by the sensor and show it on the display as the focal length of the lens. The instrument would be tested on five lenses that have focal length specifications of 100 mm, 150 mm, 200 mm, 250 mm and 300 mm. Based on the research wich has been done, focal length of the automatic measurement results is: 103,8 mm for the lens with the specification of focal length 100 mm and the error was 3,8%, 153,1 mm for the lens with the specification of focal length 150 mm and the error percentage is 2,1%, 203,2 mm for the lens with the specification of focal length 200 mm and the error percentage was 1,6%, 253,2 mm for the lens with the specification of focal length 250 mm and the error percentage was 1,3%, 303,5 mm for the lens with the specification of focal length 300 mm and the error percentage was 1,1%. The cause of focal point deviation is, ray from the laser was not parallel to the lens axis due to laser beam angle deviation. Keywords: focal length of biconvex lens, TEMT6000 sensor, stepper motor