Title of Invention

"A SOIL MOISTURE SENSOR FOR AUTOMATED MICRO IRRIGATION SYSTEM"

Abstract

The invention relates to a soil moisture sensor for automated micro irrigation system comprising a tensi-meter having a porous cup (1) and connecting tube (2), the said connecting tube is attached to a hole in the bottom cap (4) of a cylinder (3), the said cylinder contain a piston (5) attached to a piston rod (6) and said piston rod protruding out through a hole in the top cap (7) of the said cylinder and other end of said piston rod is threaded (13) for use of a nut ( 12) to contain assembly of springs (8) and a brass plate ( 10) with washers (9, 11) and a brass strip ( 14) fixed to said cylinder such that said brass plate and said brass strip make electrical contacts to each other, said brass plate is connected by wire ( 15) to the negative terminal of a 6-V battery (7) and said bras strip is connected by a wire ( 15) to the terminal E of a 6-V relay ( 21), said 6-V relay provided with five ports ( A to E), Ports B and C are connected by wires to the motor ( 18) of the pump and the Port D is connected by a wire to the said brass strip of the sensor throuh a three port switch ( 22) , and port D is connected by a wire { 15) to the positive terminal of said 6-V battery.

Full Text

The invention relates to a soil moisture sensor for automated micro irrigation system for use by the ordinary farmers who are not very rich or educated. Automated irrigation system is a very recent invention. Initially the automated irrigation system was used for surface Irrigation using some pneumatic control valves, which was actuated by air pressure. Then the pneumatic control valve was replaced by valves using water for actuation. of moisture sensor to automate irrigation has developed intensively over the last decade. Finally, during the last few years some works have been carried out for further improvement and develop some new technique to automate the irrigatiion system. These systems ( sensors) generally include tensiometer, the neutron probe, thermal flux devices and electrical resistance devices. Research and development by the USDA, state experiment stations and industry has produced some successful structure, controls and other devices to automatically control irrigation water on the farm. On-farm irrigation management practices should be simple in design and operation with very little maintenance. The present systems that are available for irri-gati6n managemnent practices has several disadvantages for which such systems have not been popularly adopted by the farmer,particularly in developing countries. - 2 - One of the main disadvantages is that the present system requires cumbersome field water measurements and none of which are well suited for practical applications for reasons such as cost of maintenance requirements. Another disadvantages with the present system of micro iirrigation is that there is frequent equipment malfunctioning and miscalibration making it less popular with the farmers. Yet another disadvantages with the present system of micro irrigation is that there is uncertainity in the method of operation and a lack of understanding of the principles of the equipment and its operation. A further disadvantage associated with the present system of micro irrigation management is that the operation time is high and so also cost of the equipment. A still further disadvantages associated with the present- system is that automated micro irrigation- is in its infancy and very few commercially produced systems and components are available. Therefore the main object of the present invention is to provide a simple, effective and a versatile soil moisture sensor which can readily adopted by the ordinary farmers of the developing countries. Another object of the present invention is to provide a system which automatically senses the soil moisture status and automatically starts applying water at the threshold limit and requires very little power to actuate and deactuate the motor. Yet another object of the present invention is to provide a system which should apply water only to the required level and automatically put it off. - 3 - A further object of the present invention is to provide a system of simple design for low cost construction and high reliability which can be manufactured and assembled from locally available material for a flexible, cost effective, easy to install system and does not interfere with the crop in its operation. A still further object of the present invention is to provide a system where the final operation is relatively insensitive to supply water pressure, as it actuates the micro irrigation, system which requires low water pressure at emitters. Yet a further object of the present invention is to provide a system which quickly responds to the soil moisture suction change, so that the soil moisture content can be kept within acceptable limit without allowing the tensiometer to "break". According to the present invention there is provided a soil moisture sensor for automated micro irrigation system comprising a tensiometer having a porous cup and connecting tube, the said connecting tube is attached to a hole in the bottom cap of a cylinder, the said cylinder contain a piston attached to a piston rod and said piston rod protruding out throuh a hole in the top cap of said cylinder and other end of said piston rod is threaded for use of a nut to contain assembly of springs and a brass plate with washers and a brass strip fixed to said cylinder such that said brass plate and said brass strip make electrical - 4 - contacts to each other, said brass plate is connected by wire to the negative terminal of a 6-V battery and said brass strip is connected by a wire to the terminal E of a 6-V carelay, said 6-V relay provided with five ports (- A to £) , Ports B and C are connected by wires to the motor of the pump and the port D is connected by a wire to the said brass strip of the sensor throuh a three port switchr and port D is connected by a wire to the positive terminal of said 6-V battery. The nature of the invention, its objective and further advantages residing in the same will be apparent from the following description made with reference to non-limiting exemplary embodiments of the invention represented in the accompanying'drawings: Fig. 1 shows a schematic diagram of soil moisture sensor; Fig. 2 shows electrical circuit diagram for the soil moisture sensor. SUMMARY OF_THE_INVENTION In accordance with the present invention a system has been developed which is reliable, simple to operate and have less involvement of labour. Such a system could be only an automated system which automatically senses the soil moisture status and automatically starts applying water at the threshold limit. It should apply water only unto the required level and automatically put it off. The system should be flexible, cost - 5 - 2 effective, easy to install and should not interfere with the crop. In the present invention a soil moisture sensor (SMS) has been developed particularly for the micro irrigation system. This device has been developed using common materials easily available. After going through the various options it was decided to use tensiometer for the purpose. The operating range of the tensiometer between 0 to 80 centibar is well suited range for utilization of water from soil by the crop. The suction developed inside the C tensiometer was to be used to move the piston inside a cylinder up and down using spring. The sensor developed was having a mechanical component and an electrical component. The front elevation of the sensor is shown in the Figure 1 . The porous cup (1 ) and connecting tube (2) were the standard items used in commercially available tensio-meters. The cylinder (3), the bottom cap (4) and top cap (7) were the items taken from commercially available domestic sprayer. They were made of good quality plastic. The connecting tube (2) was attached to the hole created in the bottom cap (4) using good quality adhesive. Adhesive was applied sufficiently to make it leak proof. The piston (5) was developed using leather gaskets and two discs were added for the strength. The piston rod (6) was a simple aluminium rod attached to the piston (5) using adhesive. The other end of the piston rod (6) was threaded (13) to facilitate the use of nut (12) in this - 6 - end. Different types of springs (8) in autdparts shops were used for the device. Washers (9, 11) and nuts ( 12) used were the standard ones which were easily available. The brass plate ( 10) was an ordinary one. It has holes which suited our purpose. The brass strip ( 14) was of standard size,namely a length of about 10cm.wide of 1 cm.and 1c.m thikness of 1.5c.m The connecting wires ( 15) were the standard electrical wires available. The isometric view of the electrical component is shown in the figure 2. The electrical component consisted of a 6V relay (21 ) comprising winding(19) and two relay parts ( 16, 17), a six volt battery (20) ¦ and a switch (22). The relay ( 21 ) was a commercially available one with five ports numbered A to E for the convenience. Port B and C were soldered with the wires coming from the motor (18). Port (E) was soldered with a wire which was connected to a three port switch (22). A three port switch (22) was used to disconnect the system from power ( electrical) as and when required. The positive side of the battery was connected with port E of the relay. The negative of the battery(20). was connected with the sensor. Working principle of the system and manner it is performed: When the sensor is installed in soil at the desired depth the porous cup (1 ) comes in direct contact with the soil. Before installation the water in the sensor _ 7 _ is at atmospheric pressure. The water potential of the soil in terms of pressure is 1 atmosphere or in terms of suction is zero at only fully saturated condition. This means that soil is always at some negative soil potential. Due to negative soil water potential, water from porous cup (1) is withdrawn and pressure inside the tensiometer tries to equilibrate with the soil water potential. Water in the sensor will also be at a pressure less than 1 atmosphere. As the soil dries up the soil water potential decreases further, so does the water pressure inside the sensor. When the difference between the atmospheric pressure and the pressure inside the sensor is able to create so much force as to overcome the friction force of the piston with the cylinder (3) walls, the piston (5) starts moving down. As the piston (5) moves down another force comes into play, the spring (8) force. As the piston (5) moves down the spring (8) is compressed and some force is also required for it to be compressed. That is, the soil water potential further decreases in moving the piston (5) downwards. When water is added to the soil, soil suction starts decreasing. As a result, the pressure in the sensor starts increasing',When the pressure inside the sensor increases sufficiently the difference between atmospheric pressure and pressure inside the sensor decreases and spring (18) which was compressed earlier creates a net upward force which pulls the piston (5) up. As the piston (5) moves up, the compressed spring - 8 - (8) is released and thereby the net upward force decreases. To make the piston (5) move up further, suction in water need to be decreased further, that is water is to be added further to the soil. It is seen that the piston (5) moves down when soil moisture decreases. The brass plate ( 10) comes down and finally makes contact with the brass strip ( 14). As the brass plate (10.) and brass strip ( 14) come in contact the relay circuit (21) becomes active. The brass plate ( 10) fixed at the end of the threaded part of piston rod ( 13) between the top washer ( 11) and the bottom washer (9) and a nut (12) finally fixes in position. As sufficient water is added the piston moves up, so does the brass plate ( 10) and the relay circuit (21) is broken which makes the motor 18 circuit inactive. As the brass plate ( 10) and brass strip (14) makes contact ( mechanical part of the sensor), the current starts flowing throuh the winding of the relay (21). This i creates a magnetic field which completes the electrical circuit to make the motor(18) active. As the brass plate . (10) and brass strip ( 14) contact is broken the current flowing in the winding stops. The motor (18) circuit I is, therefore, inactivated. The tensiometer of the sensor was filled with airfree (distilled) water. The airfree water was poured as gently' as possible. The water was filled upto the brim. The piston (5) was inserted in the cylinder (3) in tilted position, so that it went down as much as possible. Then - 9 - - 10 - the piston rod (6) was made totally vertical. Once the piston (5) was vertical it was pressed down. The piston (5) was leak proof as it did not go down. (If it goes down the piston (5) has to be brought out and cause of l-eakage is checked and corrected). The piston (5) was dipped in lubricating oil before placing inside the cylinder (3). The porous cup (1 ) of the equipment is placed inside the soil as quickly as possible, otherwise air may leak through. Once the sensor was installed the piston (5) started going down. It was allowed to go down till the space sufficient for the placement of the springs (8). Different kinds of springs (8) with varying spring constants were tested by using them in the sensor and the most suitable spring (8) was selected which gave optimum compression. The spring (8) was placed in the , position with the help of the washer(16) and the nut (12) was tnightened, The sensor was now ready for use. Such a simple system is essential for use in developing countries which can be readily adapted without any technical time requirements by the common farmer compared to systems used in developing countries which requires measuring or obtaining quality water data, soil information, crop information and soil-water monitoring for updating schedules. The invention described hereinabove is in relation to a non - limiting embodiment and as defined by the accompanying claims. - 10 - WE CLAIM: 1 . A soi1 moisture sensor device in particular for micro irrigation system, comprising : - a porous cup (1) attached to a connecting tube (2); the porous cup (1) being insertable to with draw water component from the soi1; - a cylinder (3) having a top cap (7) and a bottom cap adhesively accommodate the connecting tube (2); - a piston (5) with a piston rod (6) disposed in the cylinder (3), the distal end of the piston rod threaded and configured to accommodate fastening means (9, 11, 12); 11. - a plurality of springs (8) disposed at a proximal and distal end of the piston rod (6) to cause movement of the piston rod (6); - a brass plate (10) disposed on the rod proximity to a brass strip (14) such that they come into electrical contact when supplied with electrical power via a connecting wire (15) from an electrical means. 2. The device as claimed in claim It wherein the electrical means comprises a relay (21)* a six volt battery (20) , and a three port switch (22), the electrical means (20, 21, 22) being connected to the pump and motor (18) of the irrigation system via the three port switch (22). 12- 3. The device as claimed in claim 1 or claim 2, wherein the relay (21) has atieast five ports (A to E), and wherein the ports (B,C) are electrically connected to the motor (18), the port (D) is connected to + side of the battery (20), the - side of the battery being connected to the brass strip (14). 4. A soil moisture sensor device in particular for micro irrigation system substantially as herein described and illustrated with reference to the accompanying drawings. The invention relates to a soil moisture sensor for automated micro irrigation system comprising a tensi-meter having a porous cup (1) and connecting tube (2), the said connecting tube is attached to a hole in the bottom cap (4) of a cylinder (3), the said cylinder contain a piston (5) attached to a piston rod (6) and said piston rod protruding out through a hole in the top cap (7) of the said cylinder and other end of said piston rod is threaded (13) for use of a nut ( 12) to contain assembly of springs (8) and a brass plate ( 10) with washers (9, 11) and a brass strip ( 14) fixed to said cylinder such that said brass plate and said brass strip make electrical contacts to each other, said brass plate is connected by wire ( 15) to the negative terminal of a 6-V battery (7) and said bras strip is connected by a wire ( 15) to the terminal E of a 6-V relay ( 21), said 6-V relay provided with five ports ( A to E), Ports B and C are connected by wires to the motor ( 18) of the pump and the Port D is connected by a wire to the said brass strip of the sensor throuh a three port switch ( 22) , and port D is connected by a wire { 15) to the positive terminal of said 6-V battery.

Documents:

01680-cal-1998 abstract.pdf

01680-cal-1998 claims.pdf

01680-cal-1998 correspondence.pdf

01680-cal-1998 description(complete).pdf

01680-cal-1998 drawings.pdf

01680-cal-1998 form-1.pdf

01680-cal-1998 form-2.pdf

01680-cal-1998 form-3.pdf

01680-cal-1998 g.p.a.pdf

01680-cal-1998 letters patent.pdf

1680-CAL-1998-FORM 15.pdf

1680-CAL-1998-FORM 27.pdf