US3447054A

US3447054A - Camera control circuit

Info

Publication number: US3447054A
Application number: US583320A
Authority: US
Inventors: Donald E Hansen; Eric G Quist
Original assignee: MOSLER RESEARCH PRODUCTS Inc
Current assignee: MOSLER RESEARCH PRODUCTS Inc; MOSLER Inc
Priority date: 1966-09-30
Filing date: 1966-09-30
Publication date: 1969-05-27
Anticipated expiration: 1986-05-27

Description

May 2 7, 1969 D. E. HANSEN. ETAL CAMERA CONTROL C IRCUIT Filed Sept. 30, 1966 ggNTORS iamz v MX ,IL M

United States Patent US. Cl. 318-269 4 Claims ABSTRACT OF THE DISCLOSURE A motor controlled circuit for automatically advancing, on a continuous or intermittent basis, film in a camera of the type used in photographic security and surveillance systems, including a motor having armature and field windings and having a driven element connectable in driving relationship with the camera film advancing mechanism; selectively operable transistor switches interconnecting a source of potential with the armature and field windings for selectively causing current to flow through the windings to energize the motor to advance the film; a control signal generator for producing pulse-type or continuous signals for controlling the conduction of the transistor switches to thereby regulate the flow of current through the windings; an armature brake circuit including a transistor adapted to selectively short-circuit the armature winding when the potential source is effectively disconnected from the armature winding; and a delay circuit connected to the transistor switch associated with the field winding for delaying the nonconduction of the field winding transistor switch for a brief interval subsequent to disconnection of the potential source and the armature winding to thereby enhance braking action.

. systems.

Photographic security and surveillance systems of the type in which this invention finds particular utility are used extensively in protecting business establishments such as banks, vaults, armored car depots, and other places which, because of the storage of large amounts of money, are frequently the subject of armed robberies. These systems generally include as their principal component one or more cameras strategically located at various positions throughout the area to be protected. For example, in a bank it is common to provide cameras at locations suitable for photographing activity in the vicinity of the bank entrance, the vault, and the various tellers cages. In this manner, people entering and leaving the bank, those approaching the tellers cage, and those near the vault area are subject to being photographed.

It has been found that the changes of apprehending one who has robbed a bank, armored car depot, or other such protected establishment are greatly increased by reason of the photographs of the robbers identity which are provided by cameras of this type. The photographs constitute a clear and unequivocal record of the robbers identity and activity, and can be enlarged and duplicated for distribution to the police, newspapers, and other groups which, directly or indirectly, aid in apprehending the robber.

However, since not all persons entering and leaving a bank or approaching a tellers cage intend to commit robbery, it is not necessary, nor desirable from a practical standpoint, that all such persons have their identity and 3,447,054 Patented May 27, 1969 activities photographically recorded. These photographic security and surveillance systems usually have, therefore, as a further principal component, control means for selectively operating the camera. Typically, the control means has two modes of operation. In one mode, called the alert mode, the control means functions to feed the film through the camera on an intermittent basis as, for example, at a rate of one frame every two seconds. This permits the recording of activity on a periodic, or noncontinuous, basis. Such recording is adequate when it is desired only to record the activity of persons who, while not engaged in the actual perpetration of a robbery, raise suspicion on other grounds, such as, by loitering in a bank lobby or vault area. Generally, a guard stationed in the bank lobby or vault area can, by unobstrusively actuating a suitably located switch, initiate operation of the camera in the alert mode without the knowledge of the individual being photographically monitored, thereby providing a record of the persons activity uninhibited by the knowledge that he is under surveillance.

In the other mode, termed the alarm mode, the camera control means functions to feed the film through the camera on a continuous basis, as for example, at a rate of four or eight frames per second, thereby enabling a continuous record of activity to be generated. Such continuous monitoring is desirable for example, during the actual progress of a bank robbery. To permit the initiation of camera operation in this mode, a foot-operated switch is usually provided in the tellers cage. The switch allows the teller to actuate the camera unbeknown to the robber, thereby initiating, without fear of reprisal, camera operation in the continuous or alarm mode.

One of the principal problems with the prior art camera control systems is that they have not afforded a sufiicient degree of compactness, reliability, and simplicity. For example, many of the prior art systems employ relatively complex electromechanical control components, such as clocks and stepping devices, for intermittently advancing the film. These devices are difiicult to maintain, have high initial cost, and do not afford the compactness, simplicity and reliability desired by present day users.

It has, therefore, been a principal objective of this invention to provide a compact and smplified camera control system having a minimum number of moving parts. This objective has been achieved in the preferred embodiment of this invention by employing a fundamentally different approach to camera control design in which the film advancing mechanism of the camera is driven by a selectively operable motor under the alternative control of electronic pulse generating and latching circuits. More specifically, this objective is achieved by interconnecting in the control circuit of a camera motor, such as in the motor armature circuit, a selectively operable switch for energizing the armature winding and, in turn, operating the camera motor and advancing the film. This selectively operable switch is responsive to the outputs of the pulse generating and the latching circuits, producing, respectively, intermittent and continuous motor operation and film advancement characteristic of the alert and alarm modes.

It has been a further principal objective of this invention to provide a camera motor control circuit'which permits the rate of film advancement to be readily varied when the camera is in the continuous or alarm mode. This objective has been accomplished in the preferred embodiment of the invention by the novel and unobvious inclusion of a multilevel voltage regulator in the armature winding portion of the control circuit. The regulator is capable of selectively applying different voltages to the motor armature winding for producing varous motor and frame speeds.

An additional objective of this invention has been to provide a camera control circuit having means, operable when the camera is in the intermittent or alert mode, for quickly arresting motor rotation after each frame advancement cycle. In the preferred embodiment of this invention this objective has been accomplished by utilizing a unique braking arrangement in which a selectively operable short-circuiting switch is connected in parallel with the armature winding. The switch is responsive to the pulse generator and effectively short-circuits the armature winding after each frame advancing cycle, quickly dissipating the kinetic energy of the motor and bring it abruptly to rest.

These and other objects and advantages of the invention will be more readily apparent from a consideration of the following detailed description of the drawing showing a preferred schematic circuit diagram of the various components of a camera motor control circuit constructed in accordance with the principles of this invention.

GENERAL DESCRIPTION The prefererd embodiment of the invention, as shown more particularly in the drawing, includes a motor having an armature winding 11 and a field winding 12. In a preferred use, the motor 10 is coupled to the film advancing mechanism of a camera (not shown) by suitable drive means in a manner disclosed in the copending application of Warren D. Novak, for Sequence Camera, filed Sept. 30, 1966, Ser. No. 583,295. 'Energization of the motor '10 for selectively powering the film advancing mechanism of the camera is controlled by a field switch 14 and an armature switch 13. The switches 14 and 13 are connected in circuit arrangement between a power supply v15 and the motor field and armature windings 12 and .11, respectively, and function to alternately connect and disconnect the power supply 15 from the motor field and armature windings 12 and 11, respectively, in response to switching signals generated by a switch control circuit .16. By varying the format of the switching signals,

' a variety of modes of motor operation are possible.

A selectively operable pulse generator 17, which constitutes one input to the switch control circuit 16, is included in the preferred embodiment of the invention for providing a periodic, or intermittent, switching signal format for producing intermittent motor operation. Specifically, the pulse generator 17 produces automatic intermittent operation of the field and armature switches 13 and 14, in turn intermittently energizing the motor windings 12 and 11, respectively, to thereby produce automatic operation of the motor and film advancing mechanism on a frame-by-frame basis. A camera drive motor brake circuit 23, also included in the preferred embodiment, functions to arrest the motion of the motor at the end of each film frame advancing cycle.

By latching the switch control circuit 16 it is possible to continuously operate the motor 10, providing uninterrupted operation of the film advancing mechanism. A bilevel series voltage regulator 20 is provided for supplying two different voltages for application to the armature winding 11 to thereby afford two different motor speeds such as, for example, four frames per second and eight frames per second, when the circuit is operated in the continuous mode.

A footage indicator control 22, which is also responsive to the switch control circuit 16, is included to provide a visual indication of the number of feet of unexposed film remaining in the camera. The footage indicator operates in synchronism with the motor 10.

DETAILED DESCRIPTION The power supply 15, more particularly, includes a center tapped step-down transformer having a primary winding 31, and a secondary winding 32. The primary winding 31 is connected across a suitable source of alternating current potential (not shown) via lines 33 and 34.

Connected in line .33 is a fuse 35 for protecting the power supply 15- against damaging over-currents. Connected in line 34 is an on-off switch 36 for controlling the energi- Zation of the power supply 15. A center tap 37 of the secondary winding 32 provides the positive output of the step-down transformer 30', the negative output being taken at line -38 which is connected to both of the secondary winding terminals 39 and 40 via rectifying diodes 41 and 42, respectively. A filtering capacitor 43 connected across the center tap 37 and the negative line 38 is provided to smooth the rectified output voltage. Thus, with the primary winding 31 of the transformer '30' connected to a suitable source of alternating current and the switch 36 in the closed position, unregulated direct current is available across the positive center tap 37 and ,the negative line 38.

The bilevel voltage regulator 20 provides regulation of the direct current output from the power supply 15, the regulator having one terminal connected directly to the negative line 38 and the other terminal connected to the positive center tap 37 via a fuse 48 and a line 49. The fuse protects the remainder of the circuit from damage due to overcurrents. The regulator 20 includes a pair of emitterfollower transistors Q-1 and Q 2. The transistor Q-1 has a collector 50 connected to the positive line 49, an emitter 51 connected to a line 52 forming the positive output of the regulator 20, and a base 53 connected to the negative line 33 via a biasing resistor 54 and to the emitter 55 of the transistor Q2. The transistor Q-2 further includes a collector 56 connected in common with the collector 50 of the transistor Q-1 to the positive line 49, and a base 57 alternately connectable to terminals 58 and 59 maintained at different fixed potentials corresponding, for example, to the four frame and eight frame per second film rates, respectively. The terminals 58 andf59 constitute different tap points of a voltage divider network connected across

lines

38 and 49. The divider includes a pair of series connected Zener diodes 60 and 61 and a current limiting resistor 62.

In operation, assuming that the potential difference between

lines

49 and 38 exceeds the sum of the break-down potentials of Zener diodes 60 and 61, the Zener diodes 60 and 61,,will be continuously operated in a break-down condition with resistor 62 limiting the current and thereby preventing diode destruction. With the Zener diodes operated in the break-down region, substantially constant voltages are maintained thereacross, providing at terminal 58 a relatively fixed voltage corresponding to the breakdown voltage of Zener diode 60 and at terminal 59 a relatively fixed voltage corresponding to the sum of the break-down voltages of Zener diodes 60 and 61. Depending on the film frame rate of advancement desired, one or the other of terminals 58 or 59 is connected to the base 57 of transistor Q-Z. Since the transistor Q-2 is connected in an emitter-follower configuration, the output of transistor Q-2 taken at the emitter 55 is a function of the input to transistor Q2 at the base 57. Since the input to the base 57 is at either of two constant reference potentials, the emitter 55 of transistor Q-2 will be at either one of two fixed potentials. With a fixed potential input to the base 52 of transistor Q1, a fixed output potential input to the base 52 of transistor Q-l, a fixed output potential is present on the emitter 51 of transistor Q-l inasmuch as transistor Q-1 is also connected in an emitter-follower configuration. Hence, the output line 52 of the regulator 20, being in reality the emitter potential of transistor Q-I, is independent of the collector potential 50, which in reality is the input to the regulator on line 49. Stated differently, the regulator output on line 52 is independent of the regulator input on line 49, the regulator output on line 52 being a function only of the particular one of the reference voltage terminals 58 or 59 connected to the base 57 of transistor Q-2.

The pulse generator 17 is connected across the regulated direct

current lines

52 and 38, and includes a transistor Q-9 and a uni-junction transistor Q-10. The transistor Q-9 has an emitter 65 connected directly to the negative line 38, a collector 66 connected to the positive line 52 via a load resistor 68, and a base 69. The unijunction transistor Q- has a first base element 70 connected directly to the negative line 38 and a second base element 71 connected to the positive line 52 via a load resistor 72 and a normally open switch 73. The uni-junction transistor Q-10 further includes an emitter 74 connected to the positive line 52 via the switch 73 and a pair of series connected resistors 75 and 76. A capacitor 77 is connected between the base 69 of transistor Q9 and the emitter 74 of uni-junction transistor Q-10. The charge path of the capacitor 77 includes the variable resistor 76, the resistance of which can be varied to alter the charge time, and the base 69 and emitter 65 of unijunction transistor Q-10. The discharge path of the capacitor 77 includes a resistor 78 connected between the positive line 52 and the emitter 74 of the uni-junction transistor Q-10. The resistance of resistor 78 in part establishes the discharge time of the capacitor 77.

In operation, with switch 73 closed, the generator 17 produces pulses on generator output line 80, the spacing of which is controlled by the resistor 76 in a manner to become evident hereafter. Until the capacitor 77 charges through switch 73 and resistors 75 and 76 to the triggering level of the uni-junction transistor Q10, the transistor Q-9 is biased into conduction producing on line 80 a low level output which is substantially equal to the potential of line 38 due to the negligible emitter-collector voltage drop of conducting transistor Q-9. This low level output on line 80 corresponds to the pulse base, that is, to the potential corresponding to the space between pulse peaks. The duration of this low level output which constitutes the pulse spacing, is dependent upon the duration of transistor conduction, which in turn is dependent on the charge time of the capacitor 77, which in turn is dependent upon the resistance of the capacitor charge path. Since the capacitor charge path includes the variable resistor 76, the charge time of the capacitor 77, and, hence the pulse spacing, can be varied by merely altering the resistance of the resistor 76.

When the capacitor 77 has charged, in accordance with the polarities shown, to the triggering level of the unijunction transistor Q-10, the uni-junction transistor Q-10 fires. This allows the capacitor 77 to discharge through the uni-junction transistor for a period determined by the resistance in the capacitor discharge path which includes the emitter-base resistance of the forward biased junction formed by base 70 and emitter 74, and the resistor 78. During the period of capacitor discharge and uni-junction transistor Q-10 conduction, current is shunted from the base-69 of the transistor Q-9, driving transistor Q-9 into cut-off. With transistor Q9 in cut-01f the potential on the collector 66 rises, raising the signal on generator output line 80 to a level corresponding to the pulse peak. The width of the pulse peak, which corresponds to the period of transistor Q-9 nonconduction and uni-junction transistor Q-10 conduction, is substantially constant inasmuch as the resistance of the capacitor discharge path, which controls uni-junction conduction, and, hence, transistor nonconduction, is constant. When the capacitor 77 has fully discharged, the uni-junction transistor Q-10 is driven into cut-off once again allowing the transistor Q-9 to conduct, producing on output line 80 the low level signal corresponding to the pulse space. Thus, with switch 73 closed, pulses are continuously produced on generator output line 80 having a substantially constant pulse width and a variable pulse spacing dependent upon the setting "of resistor 76. In practice, pulse widths of 200 milliseconds and pulse spacings of two seconds have been found to be satisfactory.

The switch control circuit 16 includes a transistor Q-3, a silicon controlled rectifier SCR, a test switch 85, an end of film switch 86, and a microswitch 87. All of these circuit components, under varying conditions to be described, connect a source of control potential, namely, the negative line 38, to a junction 88 constituting the output terminal of the switch control circuit, producing switching control signals operative to control the footage indicator 22, the field and armature switches 13 and 14, and the camera motor brake 23.

The transistor Q-3 has a base 90 connected to the output line 80 of the pulse generator 17, and an emitter 91 connected directly to the negative line 38. The transistor Q-3 further includes a collector 92 connected to the positive line 52 via a line 93, the normally closed end of film switch 86, lines 94 and 95, a diode 96, and resistors 97 and resistor 98. The collector 92 of the transistor Q-3 is also connected via line 93, normally closed end of film switch 86, and line 94 to the output junction 88. Providing the end of film switch is closed, the transistor Q-3, each time it is driven into saturation in response to a positive pulse on line 80 output from the generator 17, efiectively couples the negative line 38 to the line 94, providing at junction 88 a negative output for actuating the footage indicator 22, the field and armature switches 13 and 14, and the brake 23.

The SCR includes a cathode 100 connected directly to the negative line 38 and an anode 101 connected to the positive line 52 via a normally closed switch 112, a resistor 102, and a diode 103. The anode 101 of the SCR is also connected to the positive line 52 via a diode 104, the switch 86, lines 94 and line 95, diode 96, and resistors 97 and 98. A triggering circuit for the SCR, which is connected between the positive line 52, the negative line 38, and the SCR gate 99, is provided. The triggering circuit includes the series connected, current-limiting resistor 105, a normally open switch 106 for turning on the SCR, and resistors 107 and 108. The normally closed switch 112 connected between the SCR anode and the resistor 102 provides a means for turning off the SCR.

The resistors 107 and 108, in addition to providing a divider for triggering the SCR when the switch 106 is closed, also act as an attenuator for transients, thereby avoiding false triggering of the SCR. A capacitor connected in parallel with the resistor 108 forms, in conjunction with the resistor 108, an RC filter network for transient suppression. Likewise, a capacitor 111 connected between the negative line 38 and the junction of the switch 106 and resistor 107, forms, in conjunction with resistors 107 and 108, an RC filter network for transient suppression. The circuit path including the resistor 102 and the diode 103 forms a holding circuit for the SCR. The diode 104, when the switch 87 is transferred from the position shown in the drawing, isolates the anode of the SCR from the negative line 38 thereby preventing the SCR from being cut-01f should it be conducting.

The SCR is triggered by momentarily closing the normally open switch 106, allowing current to flow through the

divider comprising resistors

105, 107 and 108. The current flow through the resistor 108 raises the potential on the gate 99 of the SCR to which its high voltage side is connected, triggering the SCR. The SCR when triggered conducts through the path including diode 103, resistor 102 and anode 101, effectively connecting the line 94 to the source of control potential, namely the negative line 38 via the switch 86, diode 104, and the anode 101, producing a negative output or control signal at the junction 88 for operating the footage indicator 22, the field and armature switches 13 and 14, and the armature brake 23. The SCR is cut-off by momentarily opening the normally closed switch 112, interrupting the holding circuit for the SCR, thereby terminating conduction.

The test switch 85 is connected between the junction 88 and the negative line 38. This normally open switch, when closed, acts independently of the operation of the SCR and the transistor Q-3 which is responsive to the pulse generator to provide an output at junction 88. Specifically, when closed, the test switch 85 directly connects the source of control potential, namely, the negative line 38 to the line 94 providing a negative output or control signal at the output junction 88 for actuating the footage indicator 22, the field and armature switches 13 and 14, and the armature brake 23. By reason of the direct coupling of the negative line 38 to the junction 88, the test switch acts irrespective of the state of conduction of the SCR and the transistor Q3. The test switch 85 is useful, for example, when it is desired for test purposes, to operate the footage indicator 22 and the motor when no unexposed film is present in the camera. Such operation is otherwise impossible due to the switch 86 which opens when no unexposed film remains in the cameras, decoupling any coupling between junction 88 and negative line 38 which might exist through either the conducting SCR or the conducting transistor Q-3.

The microswitch 87 includes a contact 115 connected at one end to the negative line 38 and at the other end alternately to a normally open contact 116 and a normally closed contact 117. A cam 119, which is located in the camera and driven at the rate of one revolution per frame actuates the switch 87 transferring the contact 115 in a manner to be described. The cam 119 is shown in the position it occupies at the beginning and end of the frame advancement cycle. The contact 117 is connected to the base 120 of a transistor Q-6 via a resistor 121 and a capacitor 122. With the contact 115 in the position shown, contact 117 couples the source of control potential, namely, the negative line 38 to the base circuit of transistor Q-6 conditioning transistor Q-6 for conduction. The contact 116 is connected to line 94 coupling the source of control potential, namely, the negative line 38, to the output junction when contact 115 transfers from the position shown, thereby providing a negative control signal at junction 88 for operating the footage indicator 22, the field and armature switches 13 and 14, and the brake 23. In practice, the contact 115 transfers from the position shown in the drawing at a point in the frame cycle slightly prior to the time at which pulses from the generator 17, if there are such, terminate, and re-transfers at approximately the end of the frame cycle. Thus, the motor 10 is operated for substantially an entire frame notwithstanding the width of the pulse which, in the intermittent mode of operation initiates the operation of the motor and the frame cycle, is less than the frame cycle duration.

The pulse generator 17, SCR, test switch 85, and switch 115 alone, or in combinations of two or more, function as a control signal generator for generating control signals for operating the armature brake 23, the indicator 22 and the motor 10.

The camera drive motor brake circuit 23 includes a transistor Q-7 having an emitter 130 connected directly to the positive line 52, a base 131 connected to the output junction 88 via a resistor 132, and a collector 133 connected to the base 120 of the transistor Q6. The transistor Q-6 has an emitter 135 and a collector 136, the emitter-collector path being connected in shunt with the armature winding 11. The transistor Q-7 is cut-off and the transistor Q-6 is biased for conduction, although not necessarily conducting, when the signal at the junction 88 is not at a low level corresponding to the operative condition of the camera film advancing motor. With the transistor Q-6 biased for conduction via the transferred contact 115, the armature winding 11 is short-circuited. The short-circuiting of the armature winding, which occurs at the end of each film frame, effectively enhances the braking of the motor 10. Improved braking results because the kinetic energy of the armature, which normally is dissipated via mechanical friction as the armature coasts to a stop, can be dissipated more quickly by taking advantage of the fact that the motor becomes a generator when it is no longer driven. Thus, by short-circuiting the armature winding, the generator is loaded, quickly converting the kinetic energy into electrical energy which is dissipated through the transistor Q-6. When the motor 10 is actuated by the presence of a negative signal at junction 88 which switches on field armature switches 13 and 14, the brake is disabled. Specifically, the transistor Q7 is switched from cut-ofi to saturation, biasing transistor Q6 to cut-ofi, and thereby terminating the armature winding short-circuit connection. The function of the capacitor 122 is to provide a high pulse of base current to the transistor Q-6 during braking, insuring complete saturation of the transistor Q-6 without the need for making the resistor 121 a small, high Wattage resistor.

The motor 10, in addition to the armature or control winding 11 and the field winding 12, also includes a'diode 138 in shunt with the armature winding 11 and a diode 139 in shunt with the field winding 12. The diodes 138 and 139 prevent unduly high and damaging transient voltages, which are generated as a result of the inductive kick produced when the current in the motor windings ceases, from being applied to the transistors Q4 and Q5. The diodes 138 and 139 perform this protective function by providing a shunt path to the negative line 38 for any of the reverse polarity transients produced by the inductive kick of the windings 11 and 12, thereby avoiding the application of these transients to the transistors Q4 and Q5.

The field winding switch 14 includes a transistor Q-S having a collector 140 connected to the winding 12 and to the cathode of the diode 139, a base 141 connected to the output junction 88 via a resistor 142, a diode 143 and line 95, and an emitter 146 connected to the positive tap line 37 via a diode 147 and a line 145. A capacitor 148 connected between the collector 1'40 and the base 141 of transistor Q-5 is provided to delay the turn-off of transistor Q-S, thereby enabling current to be present in the field Winding 12 during motor braking, enhancing the braking operation. A resistor 149 connected between the base 141 of transistor Q-S and the junction of the anode of diode 147 and the line functions in conjunction with the diode 147 to provide a reverse bias on the emitter-base junction of the transistor Q-5 thereby preventing leakage of the transistor Q5 when cut-off. Should leakage occur, the emitter 146 becomes more negative than the base 141 cutting off the transistor Q-S.

In operation, when energization of the field winding 12 is desired, the junction 88 is driven to a low potential in any one of the manners described previously, biasing the transistor Q5 into conduction thereby effectively coupling the positive line 52 to the field winding 12, completing an energization path. The bias applied to the base 141 of transistor Q-S by the low potential at junction 88 overcomes the amount of reverse bias applied to the emitterbase junction of transistor Q-5 by the diode 147 and resistor 149 combination, allowing the transistor Q5 to switch from cut-off to saturation when it is desired to energize the field winding 12.

The armature switch 14 includes a transistor Q-4 having an emitter 150 connected to the positive line 52 via a diode 151, and a collector 152 connected to the armature winding 11, the cathode of the diode 138 and the emitter 135 of transistor Q-6. The transistor Q-4 also includes a base 153 connected to the output junction 88 via the resistor 97, the diode 96, and the line 95. The resistor 98 and the diode 151 function to prevent leakage of transistor Q-4 when the transistor is cut-off by the absence of a low level signal at junction 88 in the same manner that the diode 147 and the resistor 149 prevent leakage of transistor Q-S in the absence of a low level biasing signal at junction 88. In operation, when energization of the armature winding is desired the junction 88 is driven to a low potential in any one of the manners described previously, overcoming the reverse biasing of the resistor 98 and diode 151 combination and biasing the transistor Q-4 into conduction, thereby effectively connecting the positive line 52 with the armature winding 11, completing an energization circuit to the armature winding.

The footage indicator 22 includes a motor 160 connected between the terminal 40 of the primary winding 32 of transformer 30, and a full wave rectifier 161 connected between the motor 160 and the transformer center tap 37. The rectifier 161 includes

diodes

162, 163, 164 and 165 connected in a conventional full wave rectifying bridge configuration. In addition, the rectifier includes a transistor Q8. The transistor Q8 has a collector 166 connected to the anodes of

diode

164 and 165, and an emitter 167 connected to the cathodes of

diode

162 and 163 via a diode 168, and a base 169 connected to the output junction 88 via a line 170, a resistor 171 and line 95. A resistor 173 is connected between the base 169 and the anode of diode 168. The resistor 173 and the diode 168 function to prevent leakage of transistor Q8 in the same manner as the diode 147 and the resistor 149 and the diode 151 and resistor 98 function to prevent leakage of transistor Q and Q4, respectively.

In operation, each time the motor is operated in response to the presence of a low potential control signal at junction 88, the transistor Q8 is biased into conduction via line 95, resistor 171, and line 170 allowing current to flow through the motor 160. The motor 160, in turn, drives a suitable film footage indicating element such as a pointer associated with a dial (not shown) suitably calibrated in feet of unexposed film remaining in the camera. Since the motor 160 is driven at the same speed irrespective of the particular terminal 58 or 59 to which the base 57 of the transistor Q-2 is connected, that is, irrespective of whether the film is driven at four or eight frames per second, the dial preferably has two scales, one being calibrated for the four frames per second rate and the other for the eight 'frame per second rate.

The

diodes

96, 103 and 143 prevent, when the terminal 40 is positive, a sneak bias path from being completed for the transistor Q8 during periods of motor 10 inoperativeness, thereby preventing the motor 160 from advancing and giving a false indication of the remaining unexposed film footage. Specifically, the diode 96 prevents a sneak bias path from being completed for the transistor Q8 via terminal 40, motor 160, diode 162 and 168, the emitterbase path of transistor Q8, line 170, resistor 171, 97 and 98, line 52, the emitter-collector path of transistor Q-l, line 49, fuse 48, and tap 37. The diode 103 prevents a sneak bias path from being completed for the transistor Q8 via terminal 40, footage motor 160, diodes 162 and -168, the emitter-base path of transistor Q8, line 170, resistor 171, lines 95 and 94, switch 86, diode 104, switch 112, resistor 102, line 52, the emitter-collector path of transistor Ql, line 49, fuse 48, and tap 37. The diode 143 prevents a sneak bias path from being completed for the transistor Q8 via terminal 40, footage motor 160, diodes 162 and 168, the emitter base path of transistor Q8, line 170, resistors 171, 142 and 149, line 145, and tap 37.

A lamp 180 connected across the positive and negative lines 37 and 38 in series with a footage motor controlled switch 181 is provided to indicate that a point has been reached wherein only a predetermined amount of unexposed film, such as 30 feet, remains in the cameras. In operation, the switch 181 is normally open and the lamp 180 extinguished. However, when the motor 160' rotates to the point where only 30' feet of unexposed film remains the switch 181 is closed by suitable means associated with the motor 160 (not shown) illuminating the light 180, and thereby providing a visual indication that only 30 feet of film remain in the camera.

The end of the film switch 86 is also controlled by the footage motor 160. In operation, this switch is normally closed enabling the SCR and the pulse responsive transistor Q-3 to operate the motor in either the continuously or intermittently driven modes, respectively. However, when the motor 160 has advanced to the point where no unexposed film remains, the switch 86 is tripped by the motor 160 in any suitable manner interrupting any coupling which might exist between the negative line 38 and the terminal 88 via either the trigger SCR or the intermittently operated transistor Q3. Notwithstanding the opening of normally closed switch 86 at the termination of the film roll, the motor 10- is still operable by closing the normally open test switch 85, directly couplingthe terminal 88 with the negative line 38, thereby actuating the field and armature switches 13 and 14, and, hence, the motor 10.

A lamp 184 is connected across the positive tap 37 and the negative line 38 and provides illumination for the footage indicator. This lamp is lighted wherever the switch 36 is closed. A lamp 185 is connected across the positive line 49 and negative line 38 and provides an indication that direct current power is available, that is, that switch 36 is closed and that neither fuse 35 nor 38 has blown.

OPERATION The control circuit has three principal modes of operation, namely, an intermittent mode in response to the operation of the pulse generator, a continuous mode in response to the operation of the SCR, and a test mode in response to the actuation of the test switch 85. In addition, in the latter two modes, there are two sub-modes depending upon the terminal 58 or 59 to which the base 57 of transistor Q-2 is connected. These sub-modes correspond to the four frame per second motor speed and the eight frame per second motor speed.

Operation in the intermittent mode is accomplished by closing the switch 36 which provides power to the supply 15 and the switch 73 which actuates the pulse generator 17. In practice, the switch 36 is closed whenever it is contemplated that the camera may be in use. Thus, if the camera is located in a bank lobby, the switch 36 is in the closed condition during banking hours since it is during banking hours that a bank robbery is likely to occur. The switch 73 is typically controlled by the bank teller or the bank guard and is closed when periodic, or intermittent photographing is desired such as may be the case when a suspicious-looking person enters the bank lobby and it is desired to record his activity should it later turn out that he attempts to rob the bank. Of course, the switch 73 may be kept closed if continuous surveillance is desired.

With switches 36 and 73 closed, switches and 106 open, and switch 112 closed, the pulse generator proceeds to go through its cycle, generating a pulse on line 80 of typically 200 millisecond duration for biasing transistor Q-3 into saturation and thereby effectively connecting the negative line 38 to the junction 88 for switching transistors Q4, Q5, Q-7 and Q8 into conduction. The switching of transistor Q7 into conduction shunts current from the base of transistor Q6, switching transistor Q6 into cutoff and thereby terminating the short-circuit on the armature winding 11 of the motor, effectively terminating the braking action. Prior to the switching of transistor Q6 in response to transistor Q7 being driven into conduction, transistor Q6 biased for conduction via

contacts

115 and 117 of switch 87, although not actually conducting since transistor Q4 is cut-off preventing current How in the armature winding.

The switching of transistors Q4 and Q5 into conduction effectively connects the windings 11 and 12 to the positive lines 52 and 37, respectively, allowing current to flow through the windings 11 and 12 energizing the motor 10 As the motor 10 becomes actuated, the cam 119 begins to rotate and, prior to the termination of the pulse on line 80, transfers the contact 115 from the normally closed contact 117 to the normally open contact 116, thereby coupling the negative line 38 to the junction 88 via the line 94 maintaining the conducting state of tran istors Q4, -s, Q7 and Q-8.

The switching of transistor Q8 into conduction enables current to flow through the full wave rectifier 161 and, hence, through the footage motor causing the footage indicating pointer to move in synchronism with the camera film advancement assembly driven by the motor 10.

Subsequent to the transfer of contact 115, which occurs after a brief interval due to cam 119' being rotated by the film advancing mechanism of the camera, the pulse on line 80 terminates driving transistor Q3 into cut-off effectively decoupling the negative line 38 to the output junction 88 via the line 94, the normally closed switch 86, line 93 and the emitter-collector path of transistor Q3. This decoupling, however, does not switch transistors Q4, Q5, Q7 and Q8 due to the coupling of junction 88 to the negative line 38 via the transferred contact 115, normally open contact 116 and line 94.

When the cam 119 has completed one revolution and returned to the position shown in the drawing corresponding to a single operational cycle, or the advancement of the film one frame, the contact 115 retransfers to the position shown in the drawing, decoupling the junction 88 from the negative line 38, and thereby removing the bias from transistors Q4, Q5, Q-7 and Q8, which tends to drive them from saturation to cut-off. The removal of bias from the transistor Q-8 immediately disables the full wave rectifier 161 preventing any further current flow through motor 160 and, hence, terminating the operation of the footage indicator 22. The removal of the bias from the base circuit of transistor Q4, likewise, immediately drives transistor Q4 into cut-off, effectively open-circuiting the armature winding circuit due to the high impedance of the emitter-collector path of transistor Q4. The removal of bias from the base circuit of transistor Q7 immediately drives transistor Q7 into cutoff, which in turn drives transistor Q-6 into conduction effectively short circuiting the armature winding 11 of the motor to effect braking action.

The removal of bias from the base circuit of transistor Q is not however, immediately effective to switch transistor Q-5 into cut-off due to the presence of capacitor 148 which effectively delays the outing-off of transistor Q5. The delaying of the cut-off of transistor QS functions to permit field current to flow in the field winding 12 of the motor for a brief period to enhance the braking action of the short-circuited armature winding 11, the armature winding being short-circuited by the emittercollector path of transistor Q6 biased into saturation via

contacts

115 and 117. The delay introduced by capacitor 148 is substantially coextensive with the time required to arrest the motion of the armature of the motor 10.

With the motor armature having terminated its motion, the circuit is ready for another cycle of operation in response to the occurrence of the next pulse, which typically occurs after a duration of, for example, two seconds corresponding to the spacing between pulses. The occurrence of the second pulse causes the

motors

10 and 160 to be energized for another cycle advancing the film one frame, and suitably advancing the footage indicator, respectively. This cycle of operation of the

motors

10 and 160 continues in response to the pulses on line 80 output from the generator 17 until either the switch 73 is opened, disabling the pulse generator, or the end of the film is reached whereupon the switch 86 is opened in response to its actuation by motor 160. The opening of the switch 86 prevents the transistor Q3 from periodically coupling the junction 88 to the negative line 38 via the emitter-collector path of transistor Q-3 in response to successive pulses output on line 80 from the pulse generator 17. Thus, the opening of switch 86 in response to the end of film condition prevents further actuation of the

motors

10 and 160 in response to pulses output from the generator 17.

The continuous mode of operation is produced by closing the switch 36, which provides power to the supply 15, and in addition, momentarily closing the normally open switch 106 which effectively triggers the SCR, causing it to latch through the holding circuit including diode 103 and resistor 102 and anode 101. The switch 106 is closed when continuous photographing is desired as, for example, when a bank robbery is in progress. This switch may be a foot-actuated switch located in the bank tellers cage or it may be a money clip switch actuated when a tellers cash box is emptied. With the SCR latched by momentarily closing the switch 106, the negative line 38 is effectively and continuously coupled to the output junction 88 via the anode-cathode circuit of the SCR, diode 104, normally closed end of the film switch 86, and line 94. This coupling of the negative line to the junction 88 provides continuous bias for the transistors Q4, Q5, Q7 and Q8 holding them in the saturated condition thereby disabling the armature brake 23 and allowing energizing current to flow though the footage indicator circuit 22 and the motor windings 11 and 12 continuously advancing the footage indicator in synchronism with the film advancing activity of the camera. The exact rate of film frame advancement in this mode varies depending upon which terminal 58 or 59 is connected to the base 57 of transistor Q-2. Specifically, if terminal 58 is connected to the base 57, the film rate is eight frames per second. In contrast, if terminal 59 is utilized, the film rate is four frames per second. The continuous operation of the

motors

160 and 10 continues until either the switch 112 is momentarily opened cutting off the SCR, or the end of the film is reached whereupon the normally closed switch 86 is opened preventing the coupling of the negative line 38 and the junction 88, thereby removing the bias from the transistors Q4, Q-5. Q7 and Q-8. The removal of this bias stops the

motor

10 and 160 in the manner described previously with respect to the intermittent mode of operation.

The above operation'of the circuit in the continuous mode will exist irrespective of Whether or not the switch 73 is closed, causing the pulse generator to produce pulses on output line 80. Specifically, the continuous coupling of the negative line to the output terminal 88 existing in the continuous mode effectively overrides the intermittent coupling of the negative line 38 to the output terminal 88 via the intermittently actuated transistor Q3, causing the continue-d presence of bias at junction 88 for operating the

motors

10 and 160.

Operation in the test mode is produced by closing the switch 36 which applies power to the supply 15, and closing the normally open switch 85. With the switch 85 closed, the negative line 38 is directly coupled to the output junction 88 providing bias for the transistors Q4, Q5, Q7 and Q8, producing operation of the

motors

10 and 160, in turn advancing the footage indicator and the film at a rate determined by the particular terminal 58 or 59 to which the base 57 of transistor Q-2 is connected. This continuous operation prevails notwithstanding the open position of the end of film switch 86 which occurs when no unexposed film remains in the camera.

The operation of the circuit in either the continuous, intermittent, or test mode is terminated if the switch 36 is opened or the fuse 35 blows. The open circuiting of the primary winding by opening the switch 36 or blowing the fuse 35 removes all power from the circuit. Blowing of the fuse 48, while not removing power from the footage indicator 22, does prevent operation of the motor 10 due to interruption of the

positive tap line

37, 49, 52. In addition, in either the intermittent, continuous or test mode, when the footage indicator reaches the point corresponding to the 30 foot mark, the switch 181 is actuated by the footage motor 160, illuminating the lamp and thereby indicating that only 30 feet of unexposed film footage remains.

The principles of this invention can also be utilized to operate two or more independent cameras. Specifically, pural cameras can be operated by providing, for each camera being controlled, separate switch control circuits 16, armature brakes 23, motors 10, armature and field switches 13 and 14, and footage indicators 22. The pulse generator 17, regulator 20, and power supply 15 may be common to each camera control circuit. In operation, the various switch control circuits associated with the different cameras would control the operation of the field and armature. switches, the armature brake, and the 13 footage indicator of their respective cameras in the same manner that switch control circuit 16 controls the field and armature switches 13 and 14, armature brake 23, and the footage indicator 22.

We claim:

1. A circuit for selectively actuating a camera film advancing mechanism, said circuit comprising:

motor means having a driven element connectable in driving relationship with said camera film advancing mechanism and an armature winding responsive to the flow of current therethrough for causing said motor means to impart driving motion to said driven element for actuating said camera film advancing mechanism, said motor means further including a field winding;

a source of potential;

a control circuit having control signal generating means for producing pulse-type control signals and continuous control signals;

a first transistor having an emitter-collector path connected between said source of potential and said armature winding and having a base responsive to said control signals for alternatively operating said first transistor in states of conduction and nonconduction in response to control signals;

a second transistor having an emitter-collector path in parallel with said armature winding and having a base responsive to said control signals for biasing said transistor into conduction when said first transistor is nonconductive, thereby short-circuiting said armature winding to cause said motor means to function as a generator and effect braking when said armature winding and said potential source are eifectively disconnected by said first transistor; and

a third transistor having an emitter-collector path connected between said potential source and said field winding and having a base responsive to said control signals for alternatively operating said third transistor in states of conduction and nonconduction, said third transistor further having a delayed nonconduction characteristic for allowing current to flow in said field winding during operation of said motor means as a generator, thereby enhancing said motor braking.

2. A circuit for selectively actuating a camera film advancing mechanism, said circuit comprising:

motor means having a driven element connectable in driving relationship with said camera film advancing mechanism and an armature winding responsive to the flow of current therethrough for causing said motor means to impart driving motion to said driven element for actuating said camera film advancing mechanism, said motor means further having a field winding;

a source of potential;

2. control signal generator for signals;

selectively operable switch means interconnecting said producing control source of potential and said armature winding, said switch means being responsive to said control signal for selectively causing current to flow through said armature winding;

an armature brake having selectively operable means for short-circuiting said armature winding to effect braking when the said motor means functions as a generator while the armature of said motor means is coasting to a stop and said potential source and armature winding are disconnected;

a field winding switch including (a) a first transistor having an emitter-collector path connected between said field winding and said potential source and having a base responsive to said control signals for selectively interconnecting said potential source and said field winding, and

(b) a capacitor connected to said base which is adapted to discharge when said armature winding and said potential source are disconnected for delaying nonconduction of said transistor to allow current to flow in said field winding during operation of said motor means as a generator, thereby enhancing said motor braking.

3. The circuit of claim 2 wherein said control signal generator includes a pulse generator, and wherein said control signals are pulses having a spacing greater than the delay during which said transistor is maintained conductive by said capaci or following disconnection of said armature winding and potential source.

4. The circuit of claim 2 wherein said selectively operable switch is a second transistor having an emittercollector path connected between said armature winding and said potential source, and having a base connected to said control signal generator for alternatively rendering said second transistor conductive and nonconductive in response to said control signals, and wherein said circuit further includes a first diode and a second diode connected in parallel with said armature winding and field winding, respectively, for protecting said first and second transistors, respectively, from transient signals produced by the inductive kick of said windings when said transistors switch to nonconductive states.

References Cited UNITED STATES PATENTS ORIS L. RADER, Primary Examiner. K. L. CROSSON, Assistant Examiner.

US. Cl. X.R. 318-272, 381, 443