The soil moisture based low cost automatic irrigation system was developed by assembling the various hardware components such as raspberry pi (controller), soil moisture sensors, analog to digital convertor, temperature sensor, printed circuit board, LCD screen, membrane keys, solid state relays, solenoid valve, motor, cabinet, wires and other accessories. The programming required for controlling the valve and motor was done in the python language. Dual probe conductance based soil moisture sensors were used to record the real time soil moisture content from the field. The readout shown by the controller during calibration were 325, 516, 726, 772, 779, 808, 808 and 808 mv for 0, 5, 10, 15, 20, 25, 30, 35 and 40 per cent moisture content in the soil, respectively. Initially the difference in the readout was 58.76% followed by 40.69 %, 5.95 %, 2.20 %, 1.26 %, and 1.12 % and for next two readings it was nearly constant. The readout approaches nearly stable value after 30 per cent moisture content. The designed system was tested in the field for cabbage crop. The benefit cost ratio calculated by taking the ratio of gross monetary returns to cost of production was 2.59 for automatic micro irrigation system and 2.16 for manual micro irrigation. The total cost incurred for the design and development of the controller along with accessories was `16,058/- for 1 hectare area while systems available in the market will cost 4-8 lakhs.