Abstract:
A concise electronic timer is composed of an adjustable resistor, a supercapacitor and an electromagnetic relay. After a main power is turned off, electricity supplied from the capacitor to the relay will extend or actuate the operation of a load until the discharge of the capacitor is over. Incorporating the resistor with the other two elements, the discharge time of the capacitor can be altered linearly by the resistor, therefore, a linear arrangement of delay extension and time of activation is attained. The simple, compact and economical timer can be used for indoor and outdoor illumination, monitoring security systems, as well as actuating systems.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to time delay extension furnished by electromagnetic relays and supercapacitors, and more particularly to a linear adjustment of time delay extension and time of activation from just three electronic components.  
           [0003]    2. Related Art  
           [0004]    An electronic timer generally requires a timing circuit such as vibrator circuits consisting of resistors, capacitors, diodes, inductors, comparators and transistors, etc., to achieve the desired period of time or timing sequence. For good unit-to-unit repeatability or large time extension ranges, the circuits demand the use of closely matched transistors and capacitors, or timing capacitors with low leakages. In U.S. Pat. No. 3,970,899, which is incorporated herein as reference, a time delay extender that is an improved design over his previous version of multivibrator circuit is taught. Since the U.S. Pat. No. 3,970,899 employed many expensive and bulky electronic components for the extender, it does not satisfy features with the current trend of miniaturization, lightweight and low-cost of today&#39;s electronic devices.  
           [0005]    Supercapacitors are energy-storage devices with energy densities higher than those of conventional capacitors, and power densities higher than those of all known batteries. Because of the dual characteristics, supercapacitors may be used as a back-up power like what the batteries do, as disclosed in U.S. Pat. No. 5,608,684 for long-term data preservation in random access memory (RAM) and read only memory (ROM), devices consuming low currents from μA to a few mAs. On the other hand, supercapacitors may deliver or accept peak currents of hundreds A, for example in electric vehicles as taught in U.S. Pat. No. 6,222,334 issued to Tamagawa et al. where the particular capacitors are included in a regenerative braking system to collect waste energy. Both U.S. Pat. Nos. 5,608,684 and 6,222,334 are incorporated herein as reference.  
         SUMMARY OF THE INVENTION  
         [0006]    The instant invention presents a novel application of supercapacitors in conjunction with electromagnetic relays to form a time delay extender or an actuator, which may be used for extended illumination in garages, warehouses, hallways, homes, office and interior of automobiles, as well as in security monitoring systems, also in actuating systems after a main power therein is turned off. Duration of time delay extension or time of activation is determined collectively by both the capacitance of supercapacitors and the current consumption of relays. When an adjustable resistor is incorporated with the precedent elements, the new circuit can provide a linear adjustment of time extension or time activation. Due to the small sizes, simplicity and ruggedness of the three components proposed by the present invention, the aforementioned electronic timer is light, compact, reliable, and easy of installation and operation.  
           [0007]    The invention provides a circuit of an electronic timer powered by an external power source, wherein the electronic timer controls a connection switch, which allows the external power source to provide a power to a load through the switch. The circuit comprises: an adjustable resistor; a capacitor with sufficiently large capacitance connected to the resistor in parallel; and an electromagnetic relay, connected to the capacitor in parallel to form the electronic timer, wherein the relay controls the connection switch to an on state or an off state.  
           [0008]    In the foregoing description, the external power source charges the capacitor and activates the rely to set the switch at the on state, whereby the external power source also provides the power to the load when the switch is at the on state.  
           [0009]    When the external power source stops powering the electronic timer, the capacitor then activates the rely to maintain the switch at the on state for a duration, wherein the adjustable resistor can be used to adjust the duration. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    The present invention is best understood by reading the subsequent detailed description in referring to the accompanied drawings. Like reference numbers are used for the identical elements in the following figures.  
         [0011]    [0011]FIG. 1 is a circuit block diagram of a preferred embodiment of time delay extender using batteries as power source for both supercapacitor and load.  
         [0012]    [0012]FIG. 2 is a circuit block diagram of another preferred embodiment of time delay extender using batteries as power source for both supercapacitor and load.  
         [0013]    [0013]FIG. 3 is a circuit block diagram of a preferred embodiment of time delay extender using alternate current as power source.  
         [0014]    [0014]FIG. 4 is a circuit block diagram of a preferred embodiment of electronic timer using an adjustable resistor to provide a linear range of time delay extension. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]    Today&#39;s electronic devices are developed towards light, thin and small packages. One way to achieve the goals is through miniaturizing the devices, the other is via reducing the number of chip counts, or integrating many systems on a chip, the so-called SOC design. Timing circuit is widely used in numerous electronic devices wherein many electronic components and meticulous matching procedures are normally required. The present invention offers concise electronic timers utilizing only three electronic components for providing a linear arrangement of time delay extension and time of activation. While the discharge time of supercapacitor decides the “on” time of relay, the resistance of the adjustable resistor impart a linear range for time delay extension and for time of activation. Though the said electronic timer is not as sophisticated as the conventions timers employing flip-flop and duty-cycle modulation, the present invention nevertheless proffers a timing method with minimal and inexpensive electronic components for general applications.  
         [0016]    Supercapacitors, also known as electric double layer capacitors and ultracapacitors, can store electric charges from a few a hundredth of farad (F) up to hundreds F. As the traditional capacitors, supercapacitors can suddenly release all the stored energy resulting in very high peak currents, or they may gradually discharge in accordance with the power consumption of loads, for example relays of the present invention, leading to timing capability. Since the said capacitors are insensitive to electromagnetic interference (EMI), humidity, vibration and variation of working temperature, they are more reliable than the semiconductor-based components such as transistors and FET. Thus, the electronic timers using the supercapacitors are reliable.  
         [0017]    [0017]FIG. 1 illustrates a circuit block diagram of a preferred embodiment of time delay extender of the present invention. In FIG. 1, a circuit  10  with an electronic timer is used to control delay of power supplying to the load. As the switch  18  is switched on, battery  12  will provide electric energy simultaneously charge capacitor  14 , such as a supercapacitor, and to energize the coil  26  of an electromagnetic relay  16 . Battery  12  can be a primary battery, a secondary battery, a fuel cell or a solar cell. For the protection on the battery  12 , diode  20  is used to prevent back-flow of current from the supecapacitor  14  to the battery  12 . When current flows through the coil  26 , its pivoting pin or plate S moves from the normally-closed contact B to the normally-open contact A due to the attraction of an induced magnetic field. After the electric connection is set between S and A, battery  12 ′, which may or may not have the same type and same voltage as the batter  12 , will drive the load  24 , such as a lamp or an alarm, to lit or to buzz. As soon as the switch  18  is switched off (or open), the supercapacitor  14  then continue to supply electricity to the relay  16  to sustain the connection between S and A until the supercapacitor  14  is discharged down to a working level, so that load  24  can extend its function by a duration set by the capacitance of  14  and power consumption of  16 . If the load  24  is a lamp, people can have sufficient time of illumination to leave the area after the main power therein is turned off.  
         [0018]    In another preferred embodiment of the present invention as shown in FIG. 2, a conjunction switch with the switch  18  and the switch  30  is included in the circuit, where the switch  30  is coupled with the coil  16  in series and with the capacitor  14  in parallel. The conjunction switch is operated under the mechanism. When the switch  18  is open then the switch  30  is close and when the switch  18  is close then the switch  30  is open. In this manner, the power  12  can charge the capacitor  14  without activate the relay  16 . However, after the switch  18  is open, the switch  30  then is close. The capacitor  14  then activate the relay  16  When the switch  18  is open, the load  24  is actuated due to the electric connection between S and A, wherein the relay  16  is energized by the supercapacitor  14 . As a result, the load  24  performs its function until the discharge of the supercapacitor  14  is complete. In this configuration, actuation and time of activation of the load  24  are again controlled by the combined operation of the supercapacitor  14  and the relay  16 .  
         [0019]    Following the same scheme as described in FIG. 1, FIG. 3 shows a circuit block diagram of yet another preferred embodiment of time delay extender using alternating current  34 , such as city electricity, in lieu of battery to serve as a power source. Furthermore, in FIG. 3, a charging circuit represented by the block  32  is used for converting AC to DC and then charging both the supercapacitor  14  and the electromagnetic relay  16 . A voltage step-down and other protective or limiting circuits, such as a circuit to curtail the leakage of capacitor, may also be, for example, included in the block  32 . Such provision of energy conversation as the reduction of leakage is beneficial to limited power sources such as batteries.  
         [0020]    In the circuit, when the switch  18  is close, the AC power source  34  provides power to the AC/DC converter  32 , which then charges the capacitor  14  and activates the coil  26  of the relay  16 . As a result, the node AS and A are connected and the power source  34  powers the load  24 . When the switch  18  is open, the capacitor  14  then continuously activates the relay  16  for a certain duration until the capacitor  14  is discharged down to the cut-off level for the relay  16 .  
         [0021]    Charging electricity furnished by an AC source preferably not exceed both the rated voltages of supercapacitors and the rated currents of relays to avoid destruction of the elements. However, the supercapacitors can accept whatever charging currents so long as the charging voltages are applied by a voltage level no more than 10% higher than the rated voltages of the capacitors.  
         [0022]    Supercapacitors generally can be charged and discharged up to a million cycles or longer, thence they are maintenance-fee and endurable. Electromagnetic relays are equipped with a cut-off voltage, which is also the termination point of the discharge of supercapacitors. In other words, as the voltage across the electrodes of supercapacitors drops with discharge to below the cut-off voltage of relays, it will trigger the “off” state of relays. Thereafter, the load  24  will cease its operation as S and A are disconnected and the circuit of load is open.  
         [0023]    [0023]FIG. 4 includes an adjustable resistor  15  to form the electronic timer that can provide a linear arrangement of time delay extension, or time of activation if relay is charged only by the supercapacitor. Resistor  15  and supercapacitor  14  are connected in parallel thereby the resistance of  15  can alter the discharge time of  14  linearly. The resistances of  15  can be, for example, from 1 Ω to millions Ω so that a large time delay ranges of several orders of magnitude can be attained. As resistor  15  is set at a higher resistance, the dropping voltage of capacitor  14  will reach the cut-off voltage of relay  16  get slower, and thereby the time delay extension of load  24  is increased. The linear correlation between the time delay extension and the regulating resistance, as well as time of activation and resistance, can be calibrated easily. Thus, an electronic timing device with a controlling dial can be constructed according to the circuit block diagram of FIG. 4. Even both supercapacitors and electromagnetic relays are operated at a very low voltage, for example DC 3V or larger, the timing circuit comprised by them can extend the performance of loads operated at much higher voltages, for example AC 110V or higher. Nevertheless, no transformer is required for the aforementioned controls.  
         [0024]    Various supercapacitors, commercial and home-made devices, are incorporated with, for example, the LEG-3T of Rayex, which consumes 0.11A, in a circuit using a lamp as load as shown in FIG. 3 to demonstrate the distinctiveness of the present invention. Using a constant current of 3A, supercapacitors are charged at a given time and to 2.5V. Then switch  18  is switched off, the candescent times of lamp  24  are measured. TABLE 1 lists the results of time delay extension corresponding to different charging times of supercapacitors. Though different manufactures may utilize different materials, processes and packaging to fabricate their supercapacitor, any supercapacitor can be employed to carry out the present invention. Based on the desired range of time delay extension, people can choose supercapacitors with acceptable electric specifications, dimensions and cost.  
                                                                           TABLE 1                           Time Delay Extension and Charges Stored in Supercapacitors                                    Time                           Charg-   Delay               Electric           ing   Exten-           Supercap.   Specific-   Dimensions       Time   sion       #   Source   ations   (mm × mm)   ESR   (sec)   (sec)                    1   ELNA a     2.5 V × 20 F   18 Φ × 40   57.2   10   390                       mΩ   60   537                           180   564       2   Matsushita b     2.5 V × 10 F   18 Φ × 35   45.1   10   290                       mΩ   60   315                           180   328       3   Tokin c     5.5 V ×   28.3 Φ ×   2.47   10   35               2.2 F   18.4   mΩ   60   47                           180   50       4   Tokin c     5.5 V × 1 F   28.3 Φ ×   628   10   25                   11.1   mΩ   60   26                           180   28       5   Tokin c     5.5 V ×   21 Φ × 11   1.22   10   12               0.47 F       mΩ   60   12                           180   12       6   Home d     2.5 V × 2 F   16 Φ × 25   85.9   10   37           made           mΩ   60   49                           180   54           made           Ω   60   35                           180   46       8   Home d     2.5 V × 2 F    19 Φ × 3.2   2.66   10   13           made           Ω   60   40                           180   49       9   Electrolytic   50 V ×   35.5 Φ ×   18.2   180   1               10 4  μA   46   m Ω                                                  
 
         [0025]    There is no intention to compare the quality of supercapacitors in Table 1, it serves only to illustrate the effect of the capacitance of supercapacitors on the time delay extension. As seen in Table 1, the periods of extended incandescence of lamp  24  are principally determined by the capacitance of capacitors. The supercapacitors tested in Table 1 are in either cylindrical shape or coin type, but other configurations, for example rectangle, square or pyramid, are applicable as well. Relative to the power density of supercapacitors, the consuming current of the relay (0.11A) is considered as low load, hence the ESR (equivalent series resistance) of capacitors appears to have no influence on the time delay extension. With the small dimension of #8 supercapacitor and compact size of the relay (15 mm×19 mm×15 mm high), a concise timing circuit is thence created. For explanatory purpose, an electrolytic capacitor, #9, with 50V rated voltage and 10,000 μF nominal capacitance is tested. Same as other samples, the conventional capacitor is charged 3 minutes, yet it yields only 1 sec of time delay extension. Obviously, the conventional capacitor is too small in capacity and too bulky in dimension, it could not be used for constructing the electronic timer as supercapacitor do in the present invention.  
         [0026]    Although several preferred embodiments are described in the present invention, a number of additional applications and various modifications will be apparent to those skilled in the art. This invention is thus to be limited, not by the specific disclosure herein, but by the following appended claims.