US3387119A

US3387119A - Pulse translator for a counting apparatus

Info

Publication number: US3387119A
Application number: US431047A
Authority: US
Inventors: Michael O'brien
Original assignee: Mangood Corp
Current assignee: Mangood Corp
Priority date: 1965-02-08
Filing date: 1965-02-08
Publication date: 1968-06-04
Anticipated expiration: 1985-06-04

Description

June 4, 1968 M. O'BRIEN PULSE THANSLATOR FOR A COUNTING APPARATUS 2 Sheets-Sheet 1 Filed Feb. 8, 1965 QZDQBQO p s M 2 Y m \a w 3 Mm M wm n 95 w 5 mg W A W% r M "6 i Q1 Q A N w qm x M x L WWWQ v Rh R 3 M: N R m l mm UK /T mm mmw h% 90 5m mQ QEZEQ IT 6 Rm mm m mwmumuu mm aw 1@ Am\ \mw hm A l 9 mm a m 1 ms Q T; fiwiiw? W y WE m Q3 (g m v i Au w a H a; i w m June 4, 1968 M. OBRIEN 3,387,119

PULSE TRANSLATOR FOR A COUNTING APPARATUS Filed Feb. 8, 1965 2 Sheets-Sheet 2 3a. 39. v v

v 1L v P- V V'\ V 36 T 3 k v v V INVENTOR MICHAEL O'BRIEN United States Patent 3,387,119 PULSE TRANSLATOR FOR A COUNTING APPARATUS Michael OBrien, Grayslake, Ill., assignor to Mangood Corporation, a corporation of Illinois Filed Feb. 8, 1965, Ser. No. 431,047 9 Claims. (Cl. 235-92) ABSTRACT OF THE DISCLOSURE An electronic circuit for translating sound impulses of extremely short duration into pulses of longer duration sufficient to operate a conventional counting apparatus. Sound impulses are received by a microphone connected in a sensitive detecting stage and fed through an amplifying stage to trigger a monostable multivibrator, which, in response, produces pulses of long duration by virtue of a capacitance-resistance circuit chosen to maintain a long duration multivibrator on condition. The detecting and amplifying stages are maintained in the triggered state during the multivibrator on condition by regenerative circuitry. A follower stage and driver stage respond to the multivibrator on condition to operate a conventional counter. A recording mechanism is periodically operated to record an accumulated pulse count, while simultaneously shorting out the amplifying, multivibrator and follower stages.

This invention relates to counting apparatus and more particularly to electrical counting apparatus for accurately counting very short pulses.

In trafiic counting and similar counting operations, it is desirable to count vehicles by the sound produced in a detector tube or similar detecting member as the vehicle wheels pass over it in order to obtain rapid or high frequency count. The sound impulses produced :by passage of a vehicle wheel over a tube are of very short duration, on the order of as short as one-half microsecond. Pulses of this duration are too short to operate the types of counting equipment normally employed for traffic counting which require a counting signal on the order of thirty milliseconds. Use of more sophisticated counters capable of responding in a time as short as one-half microsecond would increase the cost beyond that which can be justified for traffic counting and similar counting operations. It is accordingly one of the objects of the present invention to provide counting apparatus which is capable of responding to an input signal of extremely short duration and which provides an output signal of much longer duration capable of operating a conventional counting device.

Another object is to provide counting apparatus in which a short input pulse triggers a monostable multivibrator which produces output pulses of predetermined magnitude capable of operating a counter.

According to a feature of the invention, the multivibrator maintains the pulse detecting stage and preferably the pulse amplifying stage in triggered condition during operation of the multivibrator. This Will prevent additional pulses, whether from the detecting microphone or from internal noises in the circuit, from actually shutting off the multivibrator before it has completed its cycle, thereby to insure accurate counting.

According to another feature of the invention, the counter includes a printing or recording mechanism which may be periodically operated to record the accumulated count and which functions to disable the counting circuit during the recording operation.

The above and other objects and features of the invention will be more readily apparent from the following description when read in connection with the accompanying drawings, in which:

ice

FIGURE 1 is a circuit diagram of counting apparatus embodying the invention;

FIGURE 3 is a view of parts in section of a pickup tube and microphone; and

FIGURES 3a to 3k are diagrams illustrating voltage characteristics at various points in the circuit of FIG- URE 1.

The circuit, as shown, is adapted to receive very short pulses on the order of one-half microsecond or more and to convert them accurately into longer pulses of predetermined amplitude which are utilized for operating a counter. The specific circuit, as shown, is particularly adapted for traffic counting in which a sound transmitting member such as a tube 10, shown in FIGURE 2, is stretched across or is embedded in a highway to transmit sound waves generated by the passage of vehicle wheels across the tube. The tube is preferably connected to a hollow housing 11 which may be of metal or any other desired material and which is formed at one end with a tubular nipple 12 over which the tube is secured. The housing 11 contains a micro-phone 13 which may be a conventional carbon pile microphone whose resistance will change in response to compression of the carbon particles for a sound pulse.

As shown in FIGURE 1, the microphone 13 is connected in a circuit with a capacitor 14 across it, between a line 15 connected to the negative side of a source of power and a line 16 which constitutes ground or the positive side of the source of power. The source of power is preferably a battery maintaining the line 15 approximately 12 volts negative relative to the line 16.

A potentiometer 17 is connected in series with microphone 13 and the adjustable wiper thereof is connected through a capacitor 18 to a line 19. The potentiometer acts as a voltage divider to adjust the sensitivity of the circuit. The voltage at the potentiometer wiper is designated point A for reference to the voltage curves as will be referred to hereinafter. The line 19 is connected to the line 15 through a resistor 21 and a rectifier 22 and to the line 16 through a similar resistor 23 and rectifier 24. A point on the line 19 between the resistors 21 and 23 is connected through a rectifier 25 to a line 26. The line 26 is connected through a capacitor 27 to the line 15 and through a resistor 28 to the line 16 with a point between the capacitor and resistor being connected to the rectifier 25 and also to the base electrode of a transistor Q1. The base of transistor Q1 is also connected through a resistor 29 and line 31 to a line 32 for a purpose to appear more fully hereinafter.

The transistor Q1 has its collector connected through a resistor 33 to the line 15, and its emitter connected through a resistor 34 to the line 16. Because of the resistor 34 which acts as an emitter swamp resistor and the resistor 28 from ground to the transistor base together with the resistor 21 from the line 15 through the rectifier 25 to the transistor base, the transistor Q1 will normally be biased to a condition in which it is conducting but just slightly conducting. I have found that by maintaining this transistor which constitutes the detector stage of the circuit in a conducting condition, the detector circuit is extremely sensitive to change in voltage due to functioning of the microphone 13 to increase its conductivity and to. trigger the subsequent sections of the circuit. The base of the transistor Q1 is designated B for purposes of illustrating the voltage conditions at that point with reference to FIG- URE 3. A point designated C between the resistor 33 and the collector electrode of transistor Q1 is connected through a capacitor 35 to a line 36 at a point therein between a rectifier 37 and a resistor 38 with which a second rectifier 39 is connected in parallel. The line 36 below the rectifier 37 is connected to the base of an amplifier transistor Q2 and is also connected through a resistor 41 to a point designated 1 in a line 42 for a purpose to appear later. The base of transistor Q2 is also connected through a resistor 43 to the line 15 and through a capacitor 44 to the line 16. Additionally, it is connected through a rectifier 45 to a line 46 for a purpose to appear hereinafter.

The collector electrode of the transistor Q2 is connected directly to the line 16 and the emitter electrode is con nected through a resistor 47 to the line 15. A point designated E between the emitter of the transistor Q2 and the resistor 47 is connected through a capacitor 48 to a line 49. The line 49 is connected through a resistor 41 having a rectifier 52 in parallel therewith to the line 15 and also through a rectifier 53 to the base of a transistor Q3 constituting a portion of a monostable multivibrator stage. The base of the transistor Q3 is connected at a point P through a resistor 54 having a capacitor 55 in parallel therewith to the line 15 and is also connected through a rectifier 56 to the line 46. Additionally, it is connected through a resistor 57 and a rectifier 58 to the line 15. The collector voltage of transistor Q3 is designated G for reference to the voltage curves of FIGURE 3 and is connected through a resistor 59 to the line 16. The emitter of transistor Q3 is similarly connected through a resistor 61 to the line 15.

A point between resistor 57 and rectifier 58 is connected through a capacitor 62 to the line 42. This line is connected through a resistor 63 to the line 15 and to the collector of a transistor Q4 whose emitter is connected through a resistor 64 to the line 16. The point I as shown lies between the collector of transistor Q4 and the resistor 62. The base of transistor Q4 whose voltage is designated H is connected through a resistor 65 and a capacitor 66 in parallel to a point in the line 32 between resistor 59 and the transistor Q3.

A point in the line 42 between transistor Q4 and resistor 63 is connected through a resistor 67 to the base of a transistor Q which constitutes a follower stage. The base of transistor Q5 is connected through a rectifier 68 to the line 46 and the emitter is connected through a resistor 69 to the line 15. The collector of transistor Q5 whose voltage is designated J is connected through a resistor 71 to the line 16 with a point between the transistor and the resistor 71 being connected to the base of a transistor Q6 which constitutes a driver stage. The emitter of transistor Q6 is connected to line 16 through a rectifier 72 and is connected to line through a resistor 73. The collector of transistor Q6 is connected through a rectifier 74 to the line 15 with a voltage point K between the transistor and rectifier being connected through a resistor 75 and a counter operating coil 76 to the line 15.

The coil 76 is adapted to receive power pulses of predetermined amplitude and to be energized thereby to operate a conventional counter and printer indicated generally at 77. The counter and printer 77 will store pulses received from the coil 76 until either at predetermined times or on command it will be actuated to record the stored pulses. This actuation may be from a remote point to transmit the stored information to the remote point but for purposes of illustration, actuation of record or printer operation is illustrated as being controlled by depression of a button 78. In addition to actuating the recording operation of the counter and printer, depression of the button 78 will close a switch 79 to complete a circuit from a negative voltage bias source shown as provided by connection of a switch to the line 15 and the line 46 through a rectifier 81. In operation, when the microphone 13 is in its normal unactuated condition, the transistor Q1 will be conducting but the current flow therethrough will be very small and the voltage at point C will be a relatively high negative voltage. When a sound impusle is received by the microphone, its resistance will temporarily be decreased so that the voltage at point A will drop very sharply and will then oscillate as indicated by the curve 3A. This initial strong negative voltage pulse will be transmitted through capacitor 18 and rectifier to the base of transistor Q1 to trigger this transistor into conductivity. The rectifier 22 connecting one side of the capacitor 18 to the line 15 provides a fast recovery path for the capacitor. The transistor Q1 will be afiected only by the first negative pulse which is a very sharp pulse as seen in FIGURE 3a on the order of one-half microsecond and the capacitor 14 across the microphone assists in tuning it to provide a response time on the order of one-half microsecond. The capacitor 27 connected between line 15 and the base of transistor Q1 helps to eliminate transients while the resistors 23 and 28 assist in stabilizing the capacitor 18.

The transistor Q2 is normally biased to cut off as the result of its emitter load resistor 47 and its base resistor 43 connected to the line 15. Transient eifects are eliminated by the capacitor 44 While the rectifiers 37 and 39 connected to the line 15 prevent premature turn-on. When the transistor Q1 is triggered to full or maximum conductivity, the voltage at point C will raise to approximately the voltage of line 16 and the capacitor 35 connected to this point will charge up from the negative voltage of line 15 through the resistor 38 which will produce a voltage drop on the order of 8 volts. This will produce a positive pulse through the rectifier 37 on the base of the transistor Q2 to trigger it into maximum conductivity. The rectifier 39 connected to the line 15 provides a rapid discharge path for the capacitor 35.

With the transistor Q2 conducting, point E will have a voltage susbtantially equal to the voltage on line 16 and will charge up the capacitor 48 through the resistor 51 which will produce a drop of approximately 7 volts. This will create a positive pulse through the rectifier 53 on the base of the transistor Q3 to trigger it into conduction. The rectifiers 52 and 53 connecting the base to the negative supply line 15 provide for fast switching time and the rectifier 52 also provides a rapid discharge path for the capacitor 48.

The base of the transistor Q4 is connected to the collector electrode of the transistor Q3 and follows the transistor Q3. When the transistor Q3 is conducting, the voltage at point G will be approximately minus 12 volts due to the connection to the line 15. The capacitor 66 connected between point G and the base of the transistor Q4 supplies the necessary triggering pulses to turn on the transistor Q4. The resistor 65 will hold Q4 turned on during the time the transistor Q3 is conducting.

With transistor Q4 conducting the voltage at point I will raise to approximately the voltage of line 16. One side of the capacitor 62 which is connected to point I will cause the capacitor to be charged through the

resistors

57 and 51. The capacitor 62 in conjunction with the

resistors

57 and 51 and together with the combined forward current transfer ratios of the transistors Q3 and Q4 provide an on time for these transistors of about 30 milliseconds which is the desired pulse length. The switching off time of this circuit which constitutes a monostable multivibrator is on the order of one-half microsecond and the switching off time is about 1 millisecond. The rectifier 58 provides a one-half millisecond discharge path for the capacitor 62 providing a rapid switching off time.

When the transistor Q3 switches on, it supplies a voltage of approximately minus 12 volts from line 15 through the resistor 29 to the point B and the base of the transistor Q1 to maintain it in conductive condition during the full 30 millisecond period. This also provides a means for permitting the microphone 13 to reach a steady state. Similarly, when the transistor Q4 switches on, it will supply a positive voltage substantially equal to the voltage on line 16 through the resistor 41 to the point D and the base of the transistor Q2 to maintain it in conductive condition for the full 30 millisecond period of the monostable multivibrator allowing it to reach a steady state. The voltages at points B and D produced by this circuit are indicated by the

voltage graphs

3b and 3d.

The transistor Q5 functions as a monostable follower.

When the monostable circuit, including the transistor Q4 is conducting, the voltage at point I which follows the curve shown at 3i will be supplied to the base of the transistor Q5 to turn it on. When it is conductive, the voltage at point I which follows the curve shown in FIGURE 3 will be transmitted to the base of the transistor Q6 to trigger it into conduction. When this transmitter conducts it will create a voltage at the point K substantially equal to the voltage on the line 16 and will cause a flow of current through the resistor 75 and the coil 76 to actuate the counter.

When the counter and printer are actuated to record the accumulated count, either on a printed record or by transmitting it to a remote point, the switch 79 will be closed and will impress a negative voltage on the line 46 through the rectifier 81. This voltage will be transmitted through rectifier 45 to the base of the transistor Q2 to bias it to an 01? condition, through the rectifier 56 to the base of transistor Q3, to bias it to non-conduction and through the rectifier 68 to the base of transistor Q5 to bias it into non-conduction. Thus, during the time the recording op eration is occurring, no additional counts can be transmitted by the circuit thereby avoiding any possible confusion in operation of the circuit or the counter and printer.

While one embodiment of the invention has been shown and described in detail, it will be understood that this is illustrative only and is not to be taken as a definition of the scope of the invention, reference being had for this purpose to the appended claims.

What is claimed is:

1. A pulse translator for a counting apparatus comprising a microphone to produce a variable resistance in response to a sound impulse of extremely short duration, a circuit connected to the microphone to produce a voltage signal in response to the sound impulse, a monostable multivibrator circuit connected to the first named circuit and triggered thereby to produce a voltage pulse of predetermined duration each time it is triggered, said voltage pulse being of sufficient duration to operate said counting apparatus.

2. A pulse translator for counting apparatus comprising in combination a microphone to produce a variable resistance in response to a sound impulse of extremely short duration, a circuit connected to the microphone to produce a voltage signal in response to the sound impulse, a monostable multivibrator circuit connected to the first named circuit and triggered thereby to produce a voltage pulse of predetermined duration each time it is triggered, said voltage pulse being of sufiicient duration to operate said counting apparatus, and recording means connected to the counting apparatus and multivibrator circuit, the recording means being operable periodically to record the pulses counted and having means to disable the multivibrator while the recording means is actuated to record the pulses.

3. A pulse translator for a counting apparatus comprising a microphone to produce a variable resistance in response to a sound impulse of an extremely short duration, a circuit connected to the microphone to produce a voltage signal in response to the sound impulse, an electronic switching device, means biasing the electronic switching device into a state of low conductivity, said circuit being connected to the electronic switching device to bias it into a state of high conductivity in response to said voltage signal, a monostable multivibrator circuit, means responsive to current flow through the electronic switching device when it is in a state of high conductivity to trigger the multivibrator circuit, said multivibrator circuit producing a voltage pulse of suflicicnt duration to operate said counting apparatus.

4. The pulse translator of claim 3 in which the output of the monostable multivibrator has regenerative circuitry feeding back to the electronic switching device to maintain it in a high state of conductivity whenever the multivibrator is in an on condition.

5. The pulse translator of claim 3 in which the counting apparatus includes recording means, means periodically to operate the recording means, and means operated by the last named means to disable the multivibrator when the recording means is operated.

6. A pulse translator for a counting apparatus comprising a microphone to produce a variable resistance in response to a sound impulse of extremely short duration, a circuit connected to the microphone to produce a voltage signal in response to changes in resistance of the microphone, an electronic switching device connected to said circuit to be triggered into high conductivity by the voltage signal, a monostable multivibrator connected to the switching device to be triggered in response to current flow therethrough when it is in a high conductivity state, the multivibrator circuit being triggered thereby to produce a voltage pulse of predetermined duration each time it is triggered, said voltage pulse being of sufiicient duration to operate said counting apparatus, and a connection from the multivibrator through the electronic switching device to maintain it in a highly conductive state while the multivibrator is operating.

7. A pulse translator for a counting apparatus comprising a microphone to produce a variable resistance in response to a sound impulse of extremely short duration, a circuit connected to the microphone to produce a voltage signal in response to changes in resistance of the microphone, an electronic switching device connected to said circuit to be triggered into high conductivity by the voltage signal, an amplifier connected to the electronic switching device to produce an electrical signal in response to current flowing through the electronic switching device when it is in a state of high conductivity, a monostable multivibrator connected to the amplifier to be triggered by the electrical signal therefrom to produce a voltage pulse of predetermined duration each time it is triggered, said voltage pulse being of sufficient duration to operate said counting apparatus, and connections from the multivibrator to the electronic switching device to maintain it in a state of high conductivity and to the amplifier to maintain it in operation.

8. The pulse translator of claim 7 including in combination, recording means, means operable periodically to actuate the recording means, and means operable by the last made means to disable the amplifier and the multivibrator when the recording means is actuated.

9. A pulse translator in accordance with claim 7 wherein said multivibrator has a capacitance-resistance circuit which maintains a long duration multivibrator on condition.

References Cited UNITED STATES PATENTS 3,024,414 3/1962 Nordqvist 340-38 X 3,105,952 10/ 1963 Kidder 3403-8 3,319,222 5/ 1967 Grant 340-38 3,322,937 5/1967 OBrien 235-92 MAYNARD R. WlLBUR, Primary Examiner.

G. J. MAIER, Assistant Examiner.