Abstract:
An improved timer device which incorporates an electronic circuit to offer the user two selectable timer modes, either one-time timing mode or repeat-cycle timing mode. The cycle interval under the a repeat-cycle timing mode can be presetted by the user. The timer device comprises two AC power control circuits to control two loads concurrently.

Description:
BACKGROUND OF THE INVENTION 
     The conventional timers are mostly mechanical type, which can not set the correct time and are easy to be out of order. Although some of conventional timers are electronic type, those timers can only be presetted several daily ON/OFF times within several specified days. There is no way for a conventional electronic timer to operate repeat-cycle timing or to control more than one load concurrently. Traditional electronic timer device can be improved to meet the special timing requirements. 
     SUMMARY OF THE INVENTION 
     The major objective of present invention is to offer a repeat-cycle timing device which can continuously operate ON and OFF actions after the cycling interval has been presetted. Therefore the timer device can be applied to air-conditioner control, electrical home appliance control and other industrial control. 
     The second objective of present invention is to offer a timer device which can concurrently control two loads. 
     In brief, in accordance with this invention there is provided two cascaded digital counters with the input of the first digital counter connected to a time-base pulse generator and the digital output of the second digital counter connected to a timing interval composition unit. Two switches can select either one of the presetted timing intervals under the repeat-cycle timing mode or one-time timing mode through the timing interval selection unit which is connected to the timing interval composition unit. A bistable circuit will change state when one of the switches sends a pulse and another switch is prevented from sending a pulse. Thereafter a resetted pulse generator will generate a positive pulse to reset two digital counters so as to complete one cycle under the repeat-cycle timing mode. The bistable circuit will only change state one time to reset the digital counters one time under the one-time timing mode. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a schematic diagram of one embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Both IC 1  and IC 2  are the same digital counters. The present invention adopts CD 4020 as an example to describe in the following: 
     CD 4020 is a 16-pinned digital counter with 14-stage digital outputs. Pin 1 is for Q 12 , pin 2  for Q 13 , pin 3 for Q 14 , pin 4 for Q 6 , pin 5 for Q 5 , pin 6 for Q 7 , pin 7 for Q 4 , pin 8 for Vss, pin 9 for Q 1 , pin 10 for pulse input, pin 11 for reset, pin 12 for Q 9 , pin 13 for Q 8 , pin 14 for Q 10 , pin 15 for Q 11 , and pin 16 for V DD . Wherein Q 1 , Q 4 , Q 5 , . . . and Q 14  represent its 14-stage digital output. The inventor herein announced that the adoption of CD 4020 in the embodiment of the present invention is not for confining the scope of the present invention but only for describing the example. Regarding other IC or electronic circuits with a similar function of CD 4020, these are also included in the present invention. 
     Block 1 is a time-base pulse generator. Time-base pulses are applied to pin 10 (pulse input pin) of IC 1  to activate the counting function of IC 1 . Pin 3 (Q 14 ) of IC 1  connects to pin 10 (pulse input pin) of IC 2 , thus the Q 14  of IC 1  is the pulse input of IC 2 . The frequency of time-base pulse input of IC 1  can be changed by adjusting variable resistor VR 1  of Block 1 so as to change the frequency of the output pulse in pin 3 of IC 1 . Therefore the frequency of the time-base pulse input of IC 2  can be changed accordingly, so as to change the presetted interval of a repeat-cycle timer which is controlled by IC 2 . IC1 along with block 1 is incorporated as a time-base pulse generator, with adjustable time-base interval for IC2 
     Pins 7, 5, 4, 6, 13, 12, 14, 15, 1, 2, and 3 of IC2 are respectively digital outputs of Q 4 , Q 5 , Q 6 , Q 7 , Q 8 , Q 9 , Q 10  Q 11 , Q 12 , Q 13 , and Q 14 . The above-mentioned digital outputs are connected to a timing interval composition unit as shown in Block 2. The said timing interval composition unit is composed of several AND Gates and diodes to result in ten different interval outputs. This timing interval composition unit is only used for example description. The same timing interval composition unit can also be achieved by incorporating other similar logic circuit. Any minor modifications which cannot be illustrated herein one by one should also be included in the scope of the present invention. 
     Block 3 is a timing interval selection unit with SW 1  which represents switch 1 and SW 2  which represents switch 2. Either SW 1  or SW 2  can be connected to one of the above-mentioned ten different interval outputs to select one of the ten different presetted intervals, for example, 5 minutes, 10 minutes, 30 minutes, 1 hour, 2 hours, 5 hours, . . . and 24 hours etc. Pin 11 of the timing interval selection unit is a null pin which is specially designed for one-time timing mode whose operation will be described in the later paragraph. Therefore both SW 1  and SW 2  have eleven different selectable positions, ten timing intervals and one null pin. 
     To facilitate the description of the embodiment of the present invention, SW 1  is assumed to be presetted in timing interval T 1  and SW 2  is assumed to be presetted in timing interval T 2  and T 1  is less than T 2 . After timing initiates and time arrives at T 1 , output of SW 1  will turn to HIGH but output of SW 2  still remain as LOW, which accordingly make input of NOT Gate NOT 2  in Block 4 (SW 1  bistable circuit trigger) HIGH and output of NOT 2  LOW, therefore diode D 7  will be ON, and input point 1, IP 1 , of the bistable circuit as shown in Block 6 will be LOW accordingly. Input of NOT gate NOT 6  in Block 5 (SW 2  bistable circuit trigger) will be LOW due to the LOW output of SW 2 , therefore output of NOT 6  will be HIGH, which will make diode D 11  OFF and input point 2, IP 2 , of the bistable circuit will be HIGH accordingly. According to the theory of a bistable circuit, output point 1, OP 1 , of the bistable circuit will be HIGH and output point 2, OP 2 , will be LOW. This bi-output state, designated as STATE 1, will remain unchanged until IP 1  turns to HIGH and concurrently IP 2  turns to LOW next time, which will make the bi-state output change, with OP 1  changed to LOW and OP 2  changed to HIGH so as to designate as STATE 2. 
     When OP 2  remains LOW in STATE 1, the Base of transistor Q 2  is also LOW which will make Q 2  OFF and accordingly deactivate relay RL 1 . Therefore reed switch of RL 1  will be connected to contact point 1 so as to turn on the Load 1 connected to power receptacle 1, REC 1  controlled by contact point 1 of reed switch of RL 1 . On the hand, Load 2 connected to power receptacle 2, REC 2  will be turned off. 
     As soon, as the bistable circuit turns to STATE 1, OP 1  will produce a square wave which thereafter be applied to a capacitor C 4 , diode D 10  in reset pulse generator, which is shown in Block 7, to generate a positive pulse. The positive pulse will then be applied to the pin 11 of IC 1  and IC 2  so as to reset two digital counters IC 1 , and IC 2  simultaneously. 
     When time arrives at T 1  again after resetting, OP 2  still remain as LOW to make diode D 5  ON. Therefore input of NOT 2  will be LOW in spite of output of SW 1  being HIGH. Output of NOT 2  will be HIGH accordingly to make D 7  OFF and thereafter IP 1  will be HIGH. In the mean time, output of SW 2  remains LOW that will keep the IP 2  HIGH just as the same operation described in the former paragraph. Therefore the bistable circuit can not be changed to STATE 2. Diode D 5  will prevent SW 1  from sending a pulse to Block 4 before SW 2  has sent a pulse to Block 5. 
     When time arrives at T 2  after resetting, output of SW 2  will turn to HIGH. Therefore input of NOT 6  will be HIGH and output of NOT 6  will be LOW to make D 11  ON. IP 2  will change to LOW accordingly but IP 1  still remains HIGH, that will change the bistable circuit to STATE 2, OP 1  to LOW and OP 2  to HIGH just as the description in the former paragraph. Then the base of Q 1  will be HIGH to make Q 2  ON, which will activate the relay RL 1 . Reed switch will hereby disconnect to a contact point 1 but connect to contact point 2, thereafter to turn off Load 1 which is connected to REC 1  and turn on Load 2 which is connected to REC 2 . 
     As soon as a bistable circuit turns to STATE 2, OP 2  will produce a square wave which thereafter is applied to a capacitor C 3  and diode D 9  to generate a positive pulse. The said positive pulse will then be applied to the pin 11 of IC 1  and IC 2  so as to reset two digital counters IC 1  and IC 2  simultaneously. According to the same operation described in the former paragraph, a diode D 13  will prevent SW 2  from sending a pulse to Block 5 before SW 1  has sent a pulse to Block 4. 
     SW 1  and SW 2  will send a pulse in turn to a trigger bistable circuit due to the operation of D 5  and D 13 , thereafter the repeat-cycle timing mode will be activated. If the SW 2  is connected to the null pin, pin 11, of timing interval selection unit, SW 2  will be incapable of sending a pulse forever. Therefore the bistable circuit will remain as STATE 1 once the STATE 1 is achieved in the first time, thereafter the one-time timing mode will be activated. 
     The operation of a switching indicator and timing indicator, as shown in Block 8, will be described as follows: In the STATE 1, during Load 1 turning-on and Load 2 turning-off, OP 2  will be LOW, which will make the negative terminal of diode D 6  LOW. If the output of pin 2 of IC 1  is LOW, the base of transistor Q 1  will be LOW. If the output of pin 2 of IC 1  is HIGH, hereby the D 6  will be ON to keep the base of Q 1  still being LOW. No matter what is output status of pin 2 of IC 1 , the base of Q 1  will always remain LOW only if the bistable circuit remains in STATE 1, so as to make Q 1  OFF and inactivate LED 2 , and OP 1  will be HIGH, which will make diode D 12  OFF. Therefore the output pulse of pin 2 of IC 1  will continuously apply to the base of Q 3  to make Q 3  ON and OFF continuously. Hereby LED 1  will blink so as to indicate STATE 1. In the STATE 2, during Load 1 turning-off and Load 2 turning-on, will deactivate LED 1  and make LED 2  blink according to the same operation described above. 
     A timer inactivating circuit is showed in Block 9. When switch SW 3  is ON, a permanent HIGH voltage will be applied to pin 11, reset pin, of IC 1  and IC 1  to inactivate the timer device. 
     A power supply circuit is shown in Block 10, the points A and B will output 10 V DC voltage to power on the timer device. When AC power is temporarily turned off, the back-up battery will offer 9 V DC voltage to support the timer device.