Patent Publication Number: US-2010127094-A1

Title: Simple automatic sprinkler assistant

Description:
The simple automatic sprinkler assistant is an apparatus to help the regular sprinkler timer to become a simple, fully automatic and zero maintenance sprinkler control system. The simple automatic sprinkler assistant combines with the regular sprinkler timer will automatically irrigate the lawn only when the Relative Humidity (RH) is below or equal certain target RH such as 70%. The simple automatic sprinkler assistant can be used to replace the rain sensor to stop the sprinkler when it rains because the RH of the air is very high when it rains. The simple automatic sprinkler assistant is connected in series and between the regular sprinkler timer and the valves. 
     BACKGROUND OF THE INVENTION 
     There is a critical need to conserve water due to limited resources of water and an increasing population; however, it is important to ensure that the plants receive the minimum amount of water required for them to remain healthy. 
     How much water is needed for each kind of plant varies, and how much water is needed to irrigate the land varies greatly with different kinds of soils, climates, temperatures, air pressures, and most importantly, the amount of moisture. Temperature and moisture determine the rate of evaporation of water from the land and plants. The hotter or drier an area is, the more water needed to irrigate the plants. To determine how much water is optimum to irrigate the plants at certain times, Relative Humidity (RH) value is an important factor. The regular sprinkler timer is rigid so it is very difficult to avoid over watering or under watering. The smart sprinkler controller is much better but expensive, complicated to use and requires extensive maintenance. The present invention solves those issues by providing a sprinkler control system very simple to operate and best of all automatic and maintenance free. If the air RH is above a certain target RH, the present invention will assist the regular sprinkler timer by stopping the sprinkler valves from watering the lawn. The target RH can be made adjustable by using a variable resistor as described in the description portion. On the other hand, the regular sprinkler timer will work as normal. 
     For different kinds of lands or plants which require varying amounts of moisture, one just simply adjusts the watering time of the regular sprinkler timer. The rest will be taken care of by the present invention. 
     REFERENCE 
       
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 7,063,271 
                 June 2006 
                 Lashgari 
               
               
                 5,853,122 
                 February 1998 
                 Caprio 
               
               
                 5,847,568 
                 Dec. 8, 1998 
                 Stashkiw, et al. 
               
               
                   
               
            
           
         
       
     
     U.S. Pat. No. 7,063,271, June 2006, Lashgari, “Moisture responsive sprinkler circuit” uses Ground humidity in the sprinkler control system. This approach has the advantage of measuring the moisture at the ground next to the roots of the plants; however, this approach has the drawbacks of the inhomogeneous of the land. The humidity at one point of the ground can be very different to the next. This disadvantage is more profound if the ground is not level. The present invention use air relative humidity to solve that problem. There is a close relationship between the air relative humidity and the ground humidity. If we carefully utilize the Relative Humidity reading, we can indirectly control the moisture of the ground. Further more, the air Relative Humidity is a very important factor for the plants. The air temperature and moisture affects the rate of evaporation of water from the land and plants. Thus the air Relative Humidity can help us to determine how much water is needed to irrigate the land with optimum results. The smart sprinkler system controller has high accuracy but expensive and requires extensive maintenance. The present invention solves that problem by introducing a very simple, low cost, simple to operate, automatic and best of all maintenance free. 
     U.S. Pat. No. 5,853,122, Caprio, Dec. 29, 1998, “Relative humidity sensitive irrigation valve control” intends to use relative humidity to control the sprinklers. The disadvantage of this invention is that it uses a humidistat and a thermostat to configure the RH of the air. This is very inconvenient and requires a lot of space. This invention uses a very small sensor to measure the RH of the air and the control circuit is very small also. 
     U.S. Pat. No. 5,847,568, Stashkiw, et al. Dec. 8, 1998, “Moisture sensor and irrigation control system”. This invention tries to measure the land moisture by the photo sensor. This approach is not very accurate. This invention uses a Relative Humidity sensor chip which gives a relative more accurate and easier method to control the sprinkler system. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein: 
         FIG. 1  is a sprinkler system including a power supply circuit and a control circuit according to the present invention. 
         FIG. 2  shows the power supply circuit for the automatic sprinkler controller according to the present invention. 
         FIG. 3  shows the block diagram of the control circuit according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing one or more preferred embodiments of the invention. The scope of the invention should be determined with reference to the claims. 
     The present invention provides a simple but effective apparatus and method to enhance the regular sprinkler timer to become a low cost, automatic, maintenance free sprinkler system controller. 
     From  FIG. 1 , a regular sprinkler timer  1  has a 24 Volt Alternate Current (AC) signals and common lines which can be used to energize the present invention by connecting to the rectifier  2  through the conductors  1 - 2 . The rectifier  2  shown in  FIG. 2  converts the 24 Volt AC into 5 Volt Direct Current (DC) provides the power for all components of the present invention. The Controller Circuit  3  shown in  FIG. 3  turns on or off the Irrigation Valves  4  by connecting or disconnecting the Ground signal to the Irrigation Valves  4 . Only one zone or valve will be turn on at a time and unlimited number of valves can be turn on sequentially. The Regular Sprinkler Timer  1  provides the Irrigation Valves  4  the Valve Signals through the conductor  1 - 4  and the Controller Circuit  3  provides the Irrigation Valves  4  the common signal through the conductor  3 - 4 . 
       FIG. 2  shows the rectifier circuit to convert 24 Volt AC to 5 Volt DC. The Rectifier diode  7  with the help of the Filter Capacitor  9  and 5.1 Volts Zener diode (or Voltage regulator) converts the 24 Volt AC into 5 Volts DC to supply power for the present invention. 
       FIG. 3  shows the brain of the present invention. Based on the capacitance of the Relative Humidity sensor chip, the RH Waveform generator  11  generates a wave form which frequency and period are dependent on the capacitance of the RH sensor which varies with the present air RH. The said waveform is connected to the input of the Retriggerable Monostable Multivibrators (RMM)  12  which is biased with external resistor and capacitor to generate a pulse which pulse width is equal to the period of the timer  11  wave form when the air RH is at the target RH (a variable resistor can be used in the place of the resistor to vary the target RH.) The results are that if the air RH is below or equal the target RH of the RMM  12 , the output of the RMM  12  is a constant high straight line. On the other hand, if the air RH is higher than the target RH of the RMM  12 , the output of the RMM  12  is pulses. The output of the RMM  12  is then connected to the input of the RMM  14 . The pulse width of the RMM  14  is configured to be longer than the possible longest time period of the wave form of the timer  11 . The output of the RMM  14  is a constant high if the input is pulses and constant low if the input is a constant (high or low.) The output of the second RMM  14  is the connected to the clock pin of the D flip flop  17  which is configured to output high at Q pin when clocked. The opposite /Q pin of the D flip flop  17  is then connected to an NPN transistor which will drive a relay. The relay will be turned on when the /Q pin of the D flip flop  17  is high and off when the /Q pin of the flip flop  17  is low. The Relay  16  turns on the Valves by allowing the common signal to go through or turns off the valves by blocking the common signal. 
     In summary, if the air RH is lower than the target RH set in the RMM  12 , the output of the RMM  12  is a constant line, the output of the RMM  14  is low, the D flip flop does not change state in which Q pin is low and /Q is high. The relay  16  will allow the common signal going through and the valves turned on. On the contrary, all the states in the above paragraph are reversed and the valves are turned off.