JPH0519754B2 - - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates generally to methods of monitoring and counting, and more particularly to counting small objects such as seeds being sown by field sowing machines.

As is known to those skilled in the art, field seeders include a series of seed shoots or seed discharge tubes, one for each row to be sown at the same time. Each of these seed chute or discharge tubes automatically dispenses individual seeds from a hopper or other seed source into individual furrows that the sower forms in the ground as it moves through the field. Various monitoring and counting arrangements have been used in the past to obtain counts of seeds dispensed by such sowing machines. Such counts are particularly useful in determining and controlling seed density so as to optimize crop yields.

The prior art has commonly used photoelectric elements to detect individual seeds passing through a seed chute or discharge tube. Such configurations typically include a light source, such as a light emitting diode (LED), on one side of the seed chute or release tube, and a photosensitive element, such as a photosensitive transistor, on the opposite side. Thus, a photosensitive element typically generates a steady state signal level in response to incident light from a light source. However, once the seed passes between the chute and the light source and the photosensitive element,
The level of light incident on the photosensitive element is temporarily reduced. Correspondingly, the normal or steady state signal level output of the photosensitive element changes temporarily.

Various electrical and electronic circuits have been devised to receive the output signal of the photosensitive element and respond to level changes caused by the passage of the seed through the seed chute. Ideally, such electronic circuitry should generate a separate signal or pulse for each seed passing through the chute. Therefore, by counting these pulses, accurate information can be obtained about the number of seeds a given shoot will dispense.

However, various problems have arisen in realizing the above-mentioned ideal situation. For example, the environment in which a field sowing machine operates is far from optimal for the photosensitive system described above. In this respect, when the seeder moves across the field, it encounters considerable mud, dust, etc. Furthermore, it is common for seed grains to be provided with various coatings, and these coatings often accumulate in the seed chute or seed release tube. In this way, it accumulates in the seed release tube. This accumulation of material in the seed discharge tube tends to interfere with the proper operation of the photosensitive system. Furthermore, as the properties of the photosensitive element and the light source change slightly over time, the ambient light level incident on the photosensitive element will change and the response of the photosensitive element to the ambient light level and the response of the photosensitive element to changes in light level due to passage of the seed will change. It also changes. If these changes are not compensated for, the response of the photosensitive element can become very unreliable.

A related problem is that of drift or change over time in the nominal characteristics of circuit elements used in electronic circuits. For example, various circuit parameters such as gain, voltage levels, etc. may change or drift slightly over time. Such drifts occur, for example, due to environmental changes, causing the circuit to deviate from optimal operation, thereby reducing the reliability of the counts obtained from the circuit.

Yet another problem is reliably counting multiple seeds that fall down the seed chute in close proximity or partially overlapping. In such cases, both the photosensitive element and the associated electronic circuitry are not fast enough to reliably generate separate counting pulses for each seed.

A related problem often occurs with relatively small, fast-moving seeds such as soybeans. Additionally, soybeans are generally distributed at relatively high speeds or densities. Therefore, the photosensitive element and its associated electronics cannot respond quickly enough to reliably count each seed.

OBJECTS AND SUMMARY OF THE INVENTION Accordingly, it is a general object of the present invention to provide a new and improved circuit for a seed sensor that substantially eliminates the problems of the prior art.

Another, more specific purpose is to respond almost exclusively to changes in the signal level from the photosensitive element due to the passage of the seed, and to be less sensitive to changes in signal level due to changes in conditions such as ambient light levels. The purpose of the present invention is to provide a circuit according to the following.

Yet another object is to provide a circuit according to the above object, which is capable of distinguishing between closely spaced or partially overlapping seeds and reliably generates separate pulses or counts corresponding to each seed. The goal is to provide the following.

A related object is to provide a fast-responsive circuit to accurately respond to small fast-moving seeds, adjacent seeds, or both.

In summary, in accordance with the above objects, an improved circuit for a seed sensor is provided, in which a light source and a photosensitive means are provided along the path of the seeds, and one or more seeds pass between the light source and the photosensitive means. In response to a temporary change in the level of light incident on the photosensitive means from the light source, the output signal level of the photosensitive means is temporarily changed. According to the invention, the circuit includes pulse generating circuit means which, in response to said change in the output signal level of said photosensitive means, generates a separate pulse signal corresponding to each change in the direction of said change in signal level. Occur. A predetermined one of these distinct pulse signals is selected for counting.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Other objects, features, and advantages of the invention will become apparent from the detailed description of the illustrated embodiments and the drawings.

As shown in FIG. 1 of the drawings, a typical field seeding machine (not shown) includes a number of seed chute or seed discharge tubes, such as discharge tube 10. When dispensing and sowing seeds, these seed chute or discharge tubes 10 are placed in the direction indicated by arrow 10.
This serves as a travel path for seeds such as seeds 12 and 14. The discharge tube 10 may be cylindrical or of other shapes and does not form part of the invention.

Additionally, in accordance with conventional practice, suitable seed detection devices are positioned at appropriate locations along the axial length of the discharge tube 10 for detecting seeds, such as seeds 12, 14, traveling along the travel path 16 of the discharge tube 10. Ru. This detection device consists of a light source 18 placed on one side of the emission tube 10 and a photosensitive element 20 placed opposite the light source 18. Preferably, the emission tube 10 is provided with suitable transparent portions or windows 22, 24 so that light from the light source 18 passes through the windows 22, 24 to the photosensitive element 20. As explained in more detail below, light source 18 preferably comprises one or more light emitting diodes (LEDs).

According to a preferred form of the invention, the photosensitive element 2
0 is constructed with photovoltaic cells, as will be explained in more detail below. Preferably, the light source 18 and the photosensitive element 20 are arranged directly opposite each other across the seed travel axis or path 16 of the discharge tube 20.
Therefore, for each element of the emission tube 10, 14 is connected to a light source 18.
and the photosensitive element 20, the photosensitive element 20
The level of incident light changes temporarily. As is well known, the photosensitive element 20, such as a photovoltaic cell, generates an ambient or steady state signal level in response to incident light from the light source 18. However, if there is a temporary blockage or change in this incident light level, a corresponding temporary change will occur in the signal level of the photocell 20.

Next, FIG. 2, which shows a novel circuit according to the present invention, will be described. The circuit of FIG. 2 is particularly useful in providing an accurate count of the number of seeds passing through the discharge tube 10 in response to the above-described output signal characteristics of the photosensitive element or photovoltaic cell 20. A photovoltaic cell 20 is connected in the schematic circuit diagram between an inverting input and a non-inverting input of a first operational amplifier (op-amp) 30 . Photocell 2
0 and the non-inverting input of the operational amplifier 30 connected to one side thereof are referenced to the circuit ground.

Opamp 30 is conveniently provided with a gain control feedback circuit including a diode 32. The anode of the diode 32 is connected to the output of the operational amplifier 30, and the cathode is connected to the inverting input of the operational amplifier 30. Therefore, operational amplifier 30 and diode 32 function as an automatic gain control circuit. For this reason, the photovoltaic cell 20 by the passage of seeds as described above
The output level of the operational amplifier changes temporarily approximately in proportion to the temporary change in the output signal level of the operational amplifier. Only the DC level of this output is affected by more gradual changes in the photoelectric output. Such gradual changes may occur due to the passage of time, changes in the circuitry due to changes in temperature or humidity, or other factors that change the level of light produced by the light source 18. Such gradual changes may also be caused by dirt, dust, etc. accumulating and partially clouding or blocking the windows 22, 24. Due to the presence of feedback diode 32, photovoltaic cell 20 operates in a substantially linear region near zero signal level.

The output of the operational amplifier 30 is the output of the second operational amplifier 34
AC-coupled to the inverting input of operational amplifier 3
The non-inverting input of No. 4 is connected to a predetermined reference voltage Vr. In this way, the second operational amplifier 3
4 receives a gain control signal from the photovoltaic cell 20 using this predetermined reference level Vr as a reference. This reference level Vr is obtained from a suitable positive voltage source +V using a voltage divider composed of resistors 81 and 83 and a smoothing capacitor 85. In the illustrated embodiment, the operational amplifier 34 is provided with a suitable current limiting input resistor 36 and feedback resistor 38, resulting in a gain of approximately two.

The output of operational amplifier 34 is coupled in series through capacitor 35 and resistor 42 to the inverting input of high gain operational amplifier 40. The non-inverting input of operational amplifier 40 is coupled via a suitable current limiting resistor 41 to the same voltage reference level Vr. This operational amplifier 40 is also provided with a feedback resistor 44, and this feedback resistor 44 is connected to the resistor 42 so that the gain is close to 40.
has been selected for. Therefore, operational amplifier 40 can respond to relatively small changes in the signal level received from operational amplifier 34 with respect to the reference voltage.

According to one feature of the invention, capacitor 35
The coupling point between the resistor 42 and the resistor 42 is coupled to the cathode electrode of the diode 46 and the anode electrode of the diode 48 of the pair of diodes 46 and 48. The remaining anode and cathode electrodes of these diodes are each coupled to the output of operational amplifier 40. Therefore, the signal at the junction of capacitor 35 and resistor 42 is clamped within one diode voltage drop in either direction. This signal will be at the reference voltage level Vr if the output signal level of the photovoltaic cell 20 does not change temporarily in response to the passage of the seed.

Referring now to FIG. 3, representative waveforms generated by the photovoltaic cells, operational amplifiers 30 and 34, and operational amplifier 40 are shown to aid in understanding the operation of the circuit components described below.

A first waveform 50 represents both the output of photovoltaic cell 20 and the output of operational amplifiers 30 and 34.
Opamps 30 and 34 invert their inputs and add the gain control and voltage comparison functions described above so that their output waveforms approximately follow the waveforms generated by photovoltaic cell 20 in response to the passage of the seed.

As previously mentioned, an important feature of the present invention is the ability to distinguish between closely spaced or partially overlapping seeds passing through the seed chute 10. In this respect,
The circuit described so far is thus able to generate separate signals suitable for counting even when seeds are close together or partially overlapping.

The first waveform 50a in FIG. 3 shows the photocell and operational amplifiers 30, 34 when one seed passes
A typical response of its subsequent circuit including On the other hand, waveform 50b shows a typical response of the circuit elements described above to the seeds of FIG. 1, as well as to a pair of adjacent or partially overlapping seeds, such as 14 seeds.

The second waveform of graph 60 shows the response of the novel circuit comprised of operational amplifier 40 and related components. This new circuit will hereinafter be referred to as the discrimination or identification circuit and will be designated in its entirety by the reference numeral 49. A first graph portion 60a represents the response of this discriminator circuit to waveform 50a thereon, and a second portion 60b represents the response to waveform 50b.

As you can see in the figure, the reference level Vr is waveform 50
and 60 as the reference or baseline in both graphs. Therefore, the waveform 50 can be considered as the output waveform of the operational amplifier 34, and the operational amplifier 34 converts this waveform or level change into the reference voltage Vr.
Compare with.

Next, in operation, the above-described discrimination or discrimination circuit operates as a switching circuit responsive to changes in the cold level Vr and the output signal level of the photovoltaic cell 20, and changes the signal or waveform 5 with respect to the reference level Vr.
A separate pulse signal is generated in response to each change in direction of zero. As can be seen in waveform 60a, waveform 50
In response to the initial positive change in a from the reference level Vr, high gain operational amplifier 40 drives its output strongly in the negative direction. When waveform 50a reaches its peak level, this means that the seed blocks maximum light. In other words, it indicates that the object has passed through a position where the light level changes to the maximum extent. At this time, the waveform 60a quickly returns to the reference level Vr. Therefore, the identification circuit responds primarily to changes in waveform 50a relative to reference level Vr. Therefore, when waveform 50a reaches its peak and no longer varies with respect to the voltage reference, circuit 49 quickly returns its output to the reference level.
Return to VR. As the seed advances further along the discharge tube 10, the waveform 50a decreases with respect to Vr and changes in a relatively negative direction. Correspondingly, circuit 49 generates a second portion of waveform 60a, which abruptly changes from the reference level Vr to the full positive direction. From the foregoing, it can be seen that the positive and negative amplitudes of waveform 60 are adjusted to the voltage reference level by the operation of feedback diodes 46 and 48.
It is approximately one diode voltage drop away from Vr. The voltage drops across these diodes are shown graphically at 62 and 6 in graph 60.
4.

Waveform graphs 50b and 60b then illustrate the response of circuit 49 to partially overlapping seeds, which is a feature of the present invention. The waveform 50b advances to a certain peak value when the first of the two seeds 12, 14 reaches the point where the greatest amount of light is intercepted, ie the point where the variation or change in light level is greatest. Thereafter, the level of waveform 5b that reaches voltage reference Vr decreases. Correspondingly, waveform 6
The first portion of 0b is approximately identical to the first portion of waveform 60a. That is, in quick response to the initial rise of waveform 50b relative to reference Vr, the output of operational amplifier 40 drops below reference Vr by a diode drop. Similar to what was described for waveforms 50a and 60a, in response to the peak or zero change level of waveform 50b, waveform 60b quickly returns to voltage reference Vr and the two seeds 12 , 14, corresponds to the falling portion of waveform 50b as the first seed passes by, and quickly rises again one diode voltage drop above Vr.

However, due to the presence of a second adjacent or partially overlapping seed 14, waveform 50b does not return to the voltage reference level. Therefore, the waveform 50b
A short zero change section or depression occurs as indicated by reference numeral 66. Correspondingly, waveform 6
0a quickly returns to the voltage reference Vr. second seed 1
4 exists, the waveform 50b is at the reference level Vr
It rises again, reaches a peak value, and then falls. Correspondingly, circuit 49 responds to the second portion of waveform 50b due to the passage of second seed 14 of waveform 60b by dropping one diode drop below reference level Vr before reaching reference level Vr. Vr
It rises one diode drop above.

From the above explanation, it can be seen that the passage of each seed causes circuit 49
turns out to generate two separate pulsed signals. Thus, for each seed passing through the discharge tube 10, a separate pulse signal suitable for counting is created. Two separate pulse signals are thus created, one positive going and one negative going pulse for each seed. For example, only pulses in the positive direction are selected and counted. Therefore, there is a one-to-one correspondence between the number of seeds and the number of pulses counted.

Returning to FIG. 2, the remaining circuit elements further process and count the output of circuit 49. Another operational amplifier 70 operates as a buffer and receives the output of the operational amplifier 40 via an integrating circuit formed by a resistor 72 and a capacitor 74 connected in series. This integrating circuit is also connected to the reference level Vr. The output of the buffer is fed back to the inverting input of the operational amplifier 70, and is also fed back to the inverting input of the operational amplifier 70 via a resistor 78 connected in series.
It is also applied to the non-inverting input of two operational amplifiers 76. The output of operational amplifier 40 is connected to the cathode of diode 80. The anode of diode 80 is connected to the inverting input of operational amplifier 76 and also to a positive voltage source via a suitable current limiting resistor 82. A suitable positive feedback resistor 84 is connected to the operational amplifier 7.
A slight hysteresis is given to the operation of 6.

In the above circuit, diode 80 and operational amplifier 76
The hysteresis causes the output of op amp 40 to switch diode 80 across a predetermined threshold level, resulting in a responsive output at op amp 76. That is, the output of operational amplifier 40 must vary sufficiently from the reference level Vr to pull the inverting input of operational amplifier 76 through the voltage drop caused by diode 80 and the built-in hysteresis. This prevents a response to a spurious or noise signal that could temporarily cause the output of the operational amplifier 40 to deviate small from the reference level Vr. Furthermore, since an integrating circuit consisting of a buffer operational amplifier 70, a resistor 72, and a capacitor 74 is provided, voltage offset from the reference level Vr of the entire circuit, fluctuation of the nominal gain of the entire circuit, that is, desired gain, leakage current, etc. will be compensated. Therefore, such circuit variations are substantially compensated for or averaged out.

The output of the operational amplifier 76 is applied to one input of a two-input exclusive OR gate 86. gate 86
Output of another 2-input exclusive OR gate 88
is given to one input of The remaining inputs of exclusive OR gate 86 are connected to circuit ground.
The output of the second exclusive OR gate 88 is provided to a switching transistor 90 via a suitable current limiting resistor 92. This switching transistor 90 can be used to generate appropriate output pulses to a counter or other suitable monitoring device (not shown).

The remaining inputs of exclusive OR gate 88 receive the output of a pulse addition or pulse multiplier circuit generally designated by the reference numeral 94. The inputs of this circuit include the output of gate 86. Briefly, when the rate of pulse generation at the output of exclusive OR gate 86 is greater than or equal to a predetermined rate, circuit 94 adds a predetermined number of pulses to the pulses reaching the output of exclusive OR gate 88. works.

When monitoring and counting seeds such as soybeans that are sown at relatively high densities or high speeds, it has been found that sometimes large numbers of seeds, or groups of seeds, pass through the sensing component of the seed discharge tube (Figure 1). reference). Therefore,
The statistical probability that some of these seeds will not be counted can be compensated for by adding a statistically determined number of pulses to the output signal of the circuit of FIG. This is done by circuit 94.

Briefly, a fast differentiator circuit consisting of resistor 96 and capacitor 98 receives the output of gate 86, inverter buffers 100, 102, diode 104, capacitor 106, and resistor 1.
08 is supplied to the one shot circuit.
This one shot output is connected to another inverter.
The signal is applied via a buffer 114 to an integrating circuit composed of a resistor 110 and a capacitor 112. The output of the integrator is applied to one input of a two-input exclusive OR gate 116. The remaining inputs of gate 116 are connected to ground. The output of exclusive OR gate 116 is: Provided to enable input E of counter integrated circuit component 118. The circuit described above enables counter 118 only when the pulse rate and therefore the speed of the seed being sensed is at or above a level indicative of the soybean planting rate.

The count input C of the counter 118 is connected to the exclusive OR gate 86 through a series connected resistor 120.
receives the output of In the illustrated embodiment, counter 118 is of the type commonly referred to as a 4520. Selected outputs Q1, Q3 of counter 118
is applied to one input of a two-input exclusive OR gate 122 by a diode 121. The remaining inputs of gate 122 are connected to ground. A time delay when passing through exclusive OR gate 122 is provided by resistor 124 and capacitor 126. It is fed back to the remaining inputs of exclusive OR gate 88 to form additional pulses as described above. This delayed output of exclusive OR gate 122 is also provided to the reset input of counter 118.

A suitable voltage pull-up is also provided on the diode at the output of counter 118, and the inverter
It is connected to buffer 130. Inverter・
Buffer 130 pulls count input C of counter 118 to ground through diode 132 to prevent the counter from operating in response to additional pulses before being reset from time-delay exclusive-or gate 122. do. Switching
Preferably, this time delay is chosen so that the additional pulse generated by counter 118 is inserted in the pulse train for transistor 90 in between the pulses available at the output of exclusive-OR gate 86.

Although the present invention has been illustrated and explained using one embodiment, the present invention is not limited to this embodiment. Those skilled in the art can make various changes from the above description,
Alternatives and variations can be considered. Such alternatives, changes, and modifications form a part of the invention insofar as they fall within the spirit and scope of the claims.

[Brief explanation of drawings]

FIG. 1 illustrates an example of a seed chute or seed discharge tube in which a photosensitive element is arranged, suitable for application of the present invention. FIG. 2 is a schematic circuit diagram of the novel circuit according to the invention. FIG. 3 is a graphical representation of the signals generated at various points in the circuit of FIG. 2 in response to the passage of a seed. Explanation of symbols, 10...Seed shoot, 12,1
4...Seed, 18...Light source, 20...Photosensitive element,
49...Discrimination circuit, 94...Pulse addition circuit.

Claims (1)

[Claims] 1. A light source and a photosensitive means are respectively arranged along the travel path of the seeds, and when one or more seeds pass between the light source and the photosensitive means, the light incident from the light source to the photosensitive means is In a seed sensor circuit in which a temporary change in signal level from a photosensitive means occurs in response to a temporary change in level: a switching circuit responsive to said change in signal level from said photosensitive means; , generating an output signal comprising one pulse signal corresponding to the onset of said change in signal level, and thereafter generating an output signal comprising a separate pulse signal corresponding to each change in direction of said change in signal level. A seed sensor circuit comprising a switching circuit.