Small and marginal farmers carry out sowing, weeding and spraying largely by hand, which is slow, costly when labour is scarce, and puts the operator in direct contact with agrochemicals. Tractor-mounted implements solve part of the problem but are too large and too expensive for fragmented holdings, and most low-cost field robots reported so far handle only one task. This paper presents the design and fabrication of a compact, battery-powered robot that carries a seed-metering unit, a rotary weeder and a two-nozzle sprayer on one mild-steel chassis. The drive is sized from a rolling-resistance and gradient analysis, which gives a required torque of about 10.2 kg·cm per wheel on a 5° slope; 12 V geared motors rated at no less than 15.3 kg·cm were therefore specified. An Arduino Mega 2560 coordinates the tools and accepts commands from an Android phone over Bluetooth, and two ultrasonic sensors stop the robot when an obstacle comes within 30 cm. At a working speed of 0.3 m/s the design delivers a theoretical field capacity of 0.054 ha/h, 20 cm seed spacing with a six-cell roller at 15 rpm, and an estimated 2.8 h of operation from a 12 V, 18 Ah battery. The indicative component cost is roughly INR 15,000, which places the machine within reach of small farms, nurseries and greenhouses.

Index Terms—agricultural robot, multipurpose farm machinery, seed metering, mechanical weeding, pesticide spraying, Arduino, Bluetooth control, small-scale farming.