Electricity: electrical systems and devices – Control circuits for electromagnetic devices – For relays or solenoids
Reexamination Certificate
2000-10-25
2002-01-01
Huynh, Kim (Department: 2836)
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
For relays or solenoids
C361S170000, C307S139000
Reexamination Certificate
active
06335855
ABSTRACT:
1. BACKGROUND OF THE INVENTION
The present invention relates to remote switch controllers, and more particularly to an improved battery powered programmable remote switch controller having extended battery life that is adaptable for use in controlling irrigation valves.
2. FIELD OF THE INVENTION
Programmable irrigation valve controllers are well known in the art. Such controllers are used to open and close irrigation valves by providing electric current to solenoids located in close proximity to the valves. Relatively large electric currents are required to activate and deactivate such solenoids. Providing this required electricity is a simple matter if an external power source is readily available, such as a power line. However, many controllers must be located at remote field locations where it is impossible or impractical to run a power line or otherwise provide an external power source. Accordingly, programmable battery powered irrigation controllers have been developed.
The most significant limitation of existing battery powered irrigation controllers is battery life. Two voltage levels are generally required by such controllers: a low voltage level (which can be supplied by batteries, e.g. 3.5 volts) to operate the programming circuitry, and a higher voltage level (which can be supplied by a second set of batteries, e.g. 9 volts) to provide the necessary electrical impulses to operate the valve solenoids. The batteries on most existing battery powered controllers must be changed every few months, making them inconvenient to maintain and potentially unreliable to depend on for controlling irrigation cycles. At least one controller has addressed the problem of conserving the low voltage batteries used to operate the computing circuitry. In U.S. Pat. No. 4,423,484 to Hamilton, the microcomputer is turned off between cycles thereby conserving the low voltage batteries. However, the Hamilton controller does not address conservation of the higher voltage batteries used to operate the solenoids.
It is typical for a battery powered irrigation controller to use charging capacitors to operate the valve latching solenoids. These are generally large capacitors of 1000 micro farads or more. Most controllers (including Hamilton) maintain these capacitors in a charged condition, ready for immediate discharge to the solenoid upon receipt of a signal from the microprocessor (see e.g. U.S. Pat. No. 4,718,454 to Appleby). In addition, in most controllers these capacitors have an uninterrupted connection back to the high voltage (e.g. 9, 12 or 18 volts) batteries from which they are charged. Both of these situations reduce the life of the high voltage batteries, and give rise to other potential problems with the controller.
It is known that all charged capacitors leak over time. This places a constant drain on the high voltage batteries to which they are connected. Such leakage significantly increases with temperature increases. Thus, a fully charged capacitor in a controller located in the middle of an unshaded field during the hot summer months can rapidly deplete the high voltage batteries, even when not in use. The larger the capacitor, the larger the leakage current. Also the higher the ambient temperature, the higher the leakage. This leakage is very significant and could be as much as hundreds of microamps. The leakage causes the capacitor to draw on the battery power supply in order to stay fully charged, thereby wasting energy and leading to the frequent need to change batteries without even any solenoid operation. Preventing this leakage would conserve the life of the high voltage batteries.
Battery operated controllers such as Hamilton use the high voltage batteries for operating both the solenoids and the electronics. Since most low power circuits operate from 3 to 5 volts DC, the high voltage batteries must be reduced and regulated, thereby wasting a considerable amount of energy. Alternatively, a low voltage battery may use a boost converter (voltage multiplier) to step up the voltage as in U.S. Pat. No. 5,572,108 to Windes.
In all controllers, the large capacitors are fully discharged in order to operate the valve solenoids. The capacitors are then recharged from the high voltage batteries. At the instant the discharge occurs, current may also be drawn directly from the high voltage batteries themselves, resulting in unnecessary depletion of the high voltage batteries.
Changing the programming for remotely placed valve controllers also poses an ever present problem. With the change of seasons come changes in the amount irrigation water needed. The additional water required during hot summer months translates to longer open times for irrigation valves. Conversely, the reduced demand for water during the winter season translates to shorter or no open times for such valves. Changes in weather and weather patterns may also affect irrigation valve run times. Also different crops have different water requirements.
In order to address the ever present need to change irrigation valve run times, some remote irrigation valve controllers include a radio receiver which remains operational at all times. In this way, a signal can be transmitted to the receiver at any time and used to change the programming (run times) of the irrigation valves. However, maintaining a radio receiver in the “on” position over long periods of time requires considerable power, and will rapidly deplete the batteries of a remotely located controller. Frequently changing the batteries requires gaining access to the controller in the field which can be messy (especially in a cold, dark and/or damp environment), and may introduce unwanted foreign or corrosive materials to the delicate circuitry inside. In addition, the receiver may pick up an errant signal resulting in improper programming. Finally, unless the controller also includes a transmitter (another drain on the batteries), there is no way to confirm the receipt of programming instructions sent via radio.
The programming of other controllers may be changed by directly accessing the controller in the field. This is typically accomplished by opening the receptacle in which the controller is located and plugging a line into the controller to download new programming. As with a battery change, accessing the controller in this way may also introduce dust, dirt, debris or other undesirable material to the delicate internal circuitry of the controller. It is therefore desirable to avoid direct physical access to the remotely located controller in the field.
The need for battery powered programmable remote control switching systems is not limited to irrigation valves. Numerous industrial, utility and commercial applications also involve remote switches which must be reliably turned on and off at scheduled times in order to initiate or terminate processes, open or close gates, etc.
SUMMARY OF THE INVENTION
The present invention overcomes the disadvantages of prior art remote switching systems by providing a battery powered controller that conserves the life of the battery(ies) which operates the internal controller circuitry as well as the external switches (e.g. latching valve solenoids), and which may be easily programmed without direct physical access to the controller that might otherwise expose the internal circuitry to unwanted foreign material.
In the preferred embodiment, two sets of batteries are used in the present invention. A first set of one or more low voltage batteries (typically 3.0 to 3.6 volts) is dedicated to the internal circuitry (e.g. microprocessor). This low voltage powers the microprocessor directly without the need for regulation which would otherwise waste energy.
A second set of one or more high voltage batteries is provided which is only used for charging the capacitors which discharge into the remote switches (e.g. to operate the solenoids). This obviates any need to reduce or regulate this battery source for use by the electronic circuitry, so this potential energy loss is avoided.
In the present invention, the large capacitors are not
Alexanian George
Carlson Eugene S.
Huynh Kim
Miller Mark D.
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