US3162772A - Electronic sequence timer - Google Patents

Description

Dec. 22, 1964 v Filed June 20. 1961 ELECTRONIC SEQUENCE TIMER C. E. SMITH, JR

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F G 3 INVENi'OR.

CHARLES E. SM'THJn Dec. 22, 1964 c. E. SMITH, JR

ELECTRONIC SEQUENCE TIMER 2 Sheets-Sheet 2 Filed June 20. 1961 FIG.4

FIG.5

FIGS

' ATTOEY United States ate 3,162,772 ELETITRGNEC SEQUENtJE Till KER Charles E. rnith, in, 26 Beach St, North Providence, R1.

Filed Tune 26, 196i, Ser. No. 113,462 5 filairns. (El. Sill-$8.5)

My present invention relates to timing devices and more particularly to a novel electronic timer.

The principal object of the present invention is to provide an electronic timing circuit which permits a wide range of sequence timing.

Another object of the present invention is to provide an electronic timing device which eliminates all mechanical means to provide a device without moving parts.

A further object of the present invention is to provide an electronic sequence timer of great accuracy and reliability.

With the above and other objects and advantageous features in View, my invention consists of a novel circuit more fully disclosed in the detailed description following in conjunction with the accompanying drawings, and more particularly defined in the appended claims.

In the drawings:

FIG. 1 is a circuit diagram of a device embodying my invention.

FIGS. 2 to 6 inclusive are circuit diagrams of alternative hook-ups of the basic circuit shown in FIG. 1.

Many machines or other mechanical or electrical devices require a sequence timer for initiating an operation in timed sequence to a basic movement or operation. Such timing devices are frequently completely mechanical and often combinations of mechanical and electrical devices. In recent years relays and tubes have been used for such timing. However, it has been found that most of these timing devices are unreliable. They will not hold the timing, they miss frequently, they cannot be reset from day to day accurately, and the various portions of the device have short life and high maintainance cost. The present invention provides a simple electronic timing device which overcomes all of the defects of the previous devices. The circuit of the present invention has great flexibility and can provide any desired timing sequence or combination of sequences.

The basic circuit of the present invention is illustrated in FIG. 1 and more particularly to the portion of the circuit to the left in FIG. 1. A direct current voltage having a positive pole 1t) and a negative pole 11 is applied by means of a switch 12 to the load 13. The voltage may be any required amount. The switch 12 may be mechanically controlled as by cams, or may be a relay, photo cell, thermostat or any other circuit connecting means. The load 13 is mounted in series with a silicon controlled rectifier 14 through lines 15 and 1d. The rectifier 14- is normally in a blocking state which does not allow the flow of current until such time that a pulse is applied through its gate 1'7. Due, therefore, to this blocking action, no current can fiow through the load 13. The full supply voltage is present across the anode-cathode of the silicon controlled rectifier 14. Across this anodecathode is a uuijunction transistor circuit. This circuit comprises a unijunction transistor 18 having a base 19 connected through the resistor Ztl to a line 21 which is in turn connected to the anode line 15. The line 21 is also connected through a variable resistor 22 to the emitter 23 of the transistor 18. The emitter 23 is also connected through a line 24 and capacitor 25 and line 26 to the negative pole 11 of the main voltage supply. The second transistor base 2'7 is connected by a line 28 to the rectifier gate 17 and also through a resistor 29 to the negative pole 11. Since a reference voltage must be supplied between the bases 12 and 27 of the transistor 18, the resistors 26 and 29 are unequal. For example, with a 20 volt supply, the resistor 20 may be 390 ohms and the resistor 29 may be 47 ohms.

With the parts thus assembled, the operation of the timer is as follows: The unijunction transistor 18 by its nature blocks the flow of current from its emitter 23 to its base 27 until this voltage is suflicient to overcome the voltage present from the base 19 to the base 27. Under these conditions the supply voltage sets up a reference voltage from the base 19 to the base 27. The capacitor 25 is charged through the variable resistor 22 until the voltage across the emitter 23 to the base 27 is sutficient. The rate of charge is controlled by varying the resistor 22. In effect the entire time sequence is thus controlled by the variable resistor 22,. When the capacitor 25 is charged so that the voltage across the emitter 23 and base 27 is sufiicient, it discharges through the emitter 23, base 27 and resistor 29. This current produces a positive pulse in the gate 17 of the rectifier 14 causing it to fire. When the rectifier 14 fires, the full voltage passes through the load 13 except for a small drop across the rectifier 14. At the same time, when the rectifier 14 has fired and is conducting there is no longer suificient voltage across it to allow the unijunction circuit to re-charge and refire. The load 13 remains energized and the unijunction circuit remains discharged until the switch 12 is opened and again reclosed to initiate another cycle.

The circuit is simple and compact requiring no mechanical parts or tubes and is readily controlled by the setting of the resistor 22. If more than one timing operation is involved the circuit can easily be duplicated as shown in FIG. 1. Here an identical circuit 30 is connected across the same supply line and will start its own timing cycle when the switch 12 is closed. In the same manner additional circuits can be connected in parallel so that the closing of the switch 12 causes all the circuits to start timing. The amount of delay or time in which the load on each circuit is energized is determined by the varying of the resistor 22 in each circuit. In this form' each circuit acts independently of the other circuits and can be made to fire in any sequence.

FIGS. 2 to 6 inclusive show the above described basic circuit used in various combinations to provide different timing sequences. These various combinations can also be combined with each other to provide complex timing sequences of any desired type. In PEG. 2 1 illustrate a hook-up in which the second circuit cannot start timing until the first circuit has fired. Additional circuits can be similarly hooked into the preceding circuit in the same manner. Thus where a machine requires a series of successive timed operations, the sequence is discontinued when any preceding circuit fails to tire. Such a hook-up can be used to avoid breakage of tools or spoilage of material. Referring to FIG. 2, the circuit 31 is identical to the one shown in FIG. 1. It comprises a source of direct current having the positive pole 32 and negative pole 33. The switch 34 controls the current passing through the load 35, anode line 36, silicon controlled rectifier 37 and cathode 38. The unijunction transistor 39 operates in the same manner and the timing is controlled by the variable resistor 40. I now place a second circuit 41 so that the positive end 42 of the load is connected to the switch 34. However, the negative line 43 is now connected to the anode line 36 of the preceding circuit instead of direct to the negative pole 33. With this hook-up the negative voltage necessary to start the circuit 41 through its timing cycle is not present until the rectifier 37 of the preceding circuit has fired. Each succeeding circuit can thus be hooked into the equivalent of the anode line 36 of the preceding circuit. ecause of this if any preceding circuit fails to operate the balance of the circuits do not time out. In a complex operation it is possible to place a lamp in parallel with each load to indicate where the timing sequence has failed. It should be noted that each circuit receives its timing and main voltage from the preceding circuit. Therefore, the rectifier 37 in the first circuit must be capable of handling the total current in the following circuits. Each succeeding rectifier must also be capable of handling the total current of all the circuits following it.

The silicon controlled rectifier is comparatively expensive. The greater the capacity, the more costly is the rectifier. Therefore, the circuit illustrated in FIG. 2 could become rather expensive where a large number of timing circuits are used. I, therefore, provide an alternative hook-up shown in FIG. 3 which produces the same result as the one shown in FIG. 2 but eliminates the need of the rectifier to handle the total current of the following circuits. In this form the basic circuit 44 is hooked up in the same manner as the one shown in FIG. 1. The following circuit 45 is hooked up so that its load 46 and rectifier 47 are connected to the main voltage supply as in the form shown in FIG. 1. However, the negative line 43 of the timing voltage is now connected to the anode line 49 of the circuit 44. Thus when the circuit 44 fires only the timing voltage is transmitted onto the circuit 45. Thus the circuit 45 cannot commence its tim ing sequence until the circuit 44 has fired. This maintains all the advantages of the circuit illustrated in FIG. 2. However, the rectifier 47 must pass only the current necessary for its own load plus a small timing current.

FIG. 4 illustrates the basic circuit hooked into an alternative timing sequence. In this form the basic circuit 50 is identical with the basic circuit shown in FIG. 1. The second circuit 51 is identical with the second circuit shown in FIG. 1. However, an additional line 52 connects the positive line of the timing circuit of the circuit 51 with the anode line 53 of the first circuit Now when the switch 55 is closed both timing circuits start to build up. When one fires it will discharge the timing current from the other one and prevent the buildup of the timing current. This will prevent the firing of the other circuit. So long as circuit 50 has not fired, circuit 51 can fire. It circuit 50 fires then circuit 51 cannot fire. Similarly, additional circuits 56 can be hooked up into the sequence. In FIG. 5 the same result is accomplished by eliminating the line from the anode to the timing circuit in each station and connecting the timing circuit directly to the anode of the preceding circuit. For example, the basic circuit 57 is connected through the line 53 to the timing portion of the circuit 59. The circuit 69 is connected to the circuit 59 in the same manner. If one circuit fires it discharges the next circuit.

FIG. 6 illustrates a pair of circuits 61 and 62 that are cross connected so that the timing circuit of the circuit 61 is connected by a line 63 to the rectifier of the circuit 62 and the timing circuit of the circuit 62 is connected by a line 64 to the rectifier of the circuit 61. With this hook-up whichever circuit fires first discharges the other so that it cannot fire.

These are some of the combinations and timing sequences which can be developed with the basic circuit shown in FIG. 1. The various combinations can be used separately or in combinations with each other. The variations are infinite. The chance of a breakdown is small and the circuit itself can be housed in a small compact unit requiring little or no care. The timing is accurate. If the variable resistor is supplied with a calibrated dial, it will be found that the timing at a given setting will always remain constant from day to day. There is no residual charge left in the timing circuit to throw off the time. In other words, the main switch can be interrupted without disturbing the timing opera tion. Another great advantage of this circuit is that the time delay set by the variable resistor is not affected by variations in the supply voltage. Other advantages of the present invention will be readily apparent to a person skilled in the art.

I claim:

1. An electronic sequence timer comprising a source of direct current having a positive and negative line, a switch in the positive line, a work load and a silicon controlled rectifier connected in series between said positive and negative lines, and a pulse discharge circuit across the anode-cathode of said rectifier for producing a positive pulse at the gate of said rectifier after a predetermined interval of time causing it to fire and allow the current to flow through the load, and a second sequence timing device connected to said positive line, the negative line of said second timing device being connected to the anode of said rectifier of said first timing device, whereby said second timing device will not time out until said first device has timed out.

2. An electronic sequence timer comprising a source of direct current having a positive and negative line, a switch in the positive line, a work load and a silicon controlled rectifier connected in series between said positive and negative lines, and a pulse discharge circuit across the anode-cathode of said rectifier for producing a positive pulse at the gate of said rectifier after a predetermined interval of time causing it to fire and allow the current to flow through the load, said pulse discharge circuit inciuding an unijunction transistor having its primary base connected to the firing gate of said silicon controlled rectifier, a resistor between the anode line of said rectifier and the secondary base of said transistor, a resistor between the primary base of said transistor and said negative current line, a variable resistor between said anode line and the emitter of said transistor, and a capacitor between said emitter and said negative current line, and a second sequence timing device connected to said source of direct current, the negative line from the primary base of the transistor and its resistor and from the capacitor of said second device being connected to the anode of said rectifier of said first described device.

3. An electronic sequence timer comprising a source of direct current hooked in series with a load and a silicon controlled rectifier, and means for applying an electrical pulse to the gate of said rectifier after a predetermined interval of time, and a second sequence timing device in series with said source of direct current, the pulse applying means of said second device being negatived by the pulsation of said pulse applying means of said first described device, whereby said second device will operate only before the operation of said first device.

4. An electronic sequence timer comprising a source of direct current having a positive and negative line, a switch in the positive line, a work load and a silicon controlled rectifier connected in series between said positive and negative lines, and a pulse discharge circuit across the anode-cathode of said rectifier for producing a positive pulse at the gate of said rectifier after a predetermined interval of time causing it to fire and allow the current to fiow through the load, and a second sequence timing device mounted between said positive and negative lines, the pulse discharge circuit of said first described device being connected across the cathode of said rectifier and the anode of the rectifier of said second timing device, the pulse discharge circuit of the second device being connected across the anode of said rectifier and the cathode of the rectifier of said second timing device, whereby the timing out of either device prevents the timing out of the other device.

5. An electronic sequence timer comprising a source of direct current having a positive and negative line, a switch in the positive line, a work load and a silicon controlled rectifier connected in series between said positive and negative lines, and a pulse discharge circuit across the anode-cathode of said rectifier for producing a positive pulse at the gate of said rectifier after a predetermined interval of time causing it to fire and allow the current to flow through the load, said pulse discharge circuit including a unijunction transistor having its primary base connected to the firing gate of said silicon controlled rectifier, a resistor between the anode line of r said rectifier and the secondary base of said transistor, a resistor between the primary base of said transistor and said negative current line, a variable resistor between said anode line and the emitter of said transistor, and a capacitor between said emitter and said negative current line, and a second sequence timing device mounted between said positive and negative lines, the pulse discharge circuit of said first described device being connected across the cathode of said rectifier and the anode of the rectifier of said second timing device, the pulse discharge circuit of the second device being connected across the anode of said rectifier and the cathode of the rectifier of said second timing device, whereby the timing out of either device prevents the timing out of the other device.

References Cited by the Examiner UNITED STATES PATENTS OTHER REFERENCES Solid State Products, Inc, Bulletin D42002, August 1959, page 15.

Silicon Controlled Rectifier, GE. Co., December 1958, page 54-.

Cartier et al.: IBM Technical Disclosure Bulletin, V01. 3, No. 6, November 1960, page 44.

GE. Controlled Rectifier Manual, 1960, FIGURE 913 on page 1964, and FIGURE 4.12(a) on page 55.

JOHN W. HUCKERT, Primary Examiner.

GEORGE N. WESTBY, ARTHUR GAUSS, Examiners.

Claims (1)

1. AN ELECTRONIC SEQUENCE TIMER COMPRISING A SOURCE OF DIRECT CURRENT HAVING A POSITIVE AND NEGATIVE LINE, A SWITCH IN THE POSITIVE LINE, A WORK LOAD AND A SILICON CONTROLLED RECTIFIER CONNECTED IN SERIES BETWEEN SAID POSITIVE AND NEGATIVE LINES, AND A PULSE DISCHARGE CIRCUIT ACROSS THE ANODE-CATHODE OF SAID RECTIFIER FOR PRODUCING A POSITIVE PULSE AT THE GATE OF SAID RECTIFIER AFTER A PREDETERMINED INTERVAL OF TIME CAUSING IT TO FIRE AND ALLOW THE CURRENT TO FLOW THROUGH THE LOAD, AND A SECOND SEQUENCE TIMING DEVICE CONNECTED TO SAID POSITIVE LINE, THE NEGATIVE LINE OF SAID SECOND TIMING DEVICE BEING CONNECTED TO THE ANODE OF SAID RECTIFIER OF SAID FIRST TIMING DEVICE, WHEREBY SAID SECOND TIMING DEVICE WILL NOT TIME OUT UNTIL SAID FIRST DEVICE HAS TIMED OUT.

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