| 摘要 |
<p>1,267,847. Watering crops. L'ELECTRONIQUE APPLIQUEE. 5 Dec., 1969 [10 Dec., 1968], No. 59583/69. Heading A1E. [Also in Divisions G1 and H3] In irrigation of crops or spraying of fruit buds in orchards, a relay 33 is energised to close a circuit 55 for the water pump only when the right conditions of temperature and ambient luminosity prevail. In the irrigation control system shown transistors 30, 31 and 32 form an AND gate so that relay 33 can be energised only when all conduct. Transistor 30 conducts only when the temperature sensed by negative temperature coefficient thermistor I exceeds a given value set by adjustment of resistor 9; transistor 31 conducts only when the ambient luminosity sensed by a photomultiplier 2 is less than a given value set by adjustment of resistor 13; and transistor 32 conducts only when the soil moisture content sensed by buried chromium electrodes 3 is less than a given value set by adjustment of resistor 14. Resistor 15 enables compensation to be made for different lengths of cable between the electrodes 3 and the rest of the apparatus. When transistors 30, 31 and 32 are all conducting, R.C. timing circuits 54, 53 and 39, 40 cause transistor 46, and thus relay 33, to be switched off and on at 30 minute intervals. For spraying, the circuit may be arranged so that transistor 30 conducts only when the temperature is below a given value.</p> |
