GB2072834A - Motion sensing apparatus with variable threshold - Google Patents

Abstract

Motion sensing apparatus comprises a mercury globule supported on an opaque concave surface having a transparent window at its lowest part. A photocell is exposed to light passing through the window as it is varied by movement of the mercury. The photocell output is passed to one terminal of a comparator, the other terminal of which is energized through a variable resistor by means of which the sensitivity of the comparator to the photocell input may be varied. The comparator output controls pulse generating apparatus which produces output pulses of controllable length or, alternatively, an electronically latched continuous output either of which may control mechanism of any kind. <IMAGE>

Description

SPECIFICATION Motion sensing apparatus with variable threshold The present invention relates to motion sensing apparatus and more particularly to improvements including a novel sensor and means for variably controlling the sensitivity of such apparatus.

The motion of a plateform upon which the sensor of the present invention is mounted is sensed by a device comprising a substantially opaque inertial element movably supported upon a concave surface which also is substantially opaque except for a translucent window area at its lowest point. The inertial element is of such size as to cover at least a portion of the window area.

A light source and photocell, shielded from light other than light from said source, are positioned on opposite sides of the window area so that upon movement of the inertial element over the window area the amount of light reaching the photocell from the source will be varied.

Signal emitting means respond to variations in the amount of light reaching the photocell from the light source. The magnitude of the light variation capable of causing the signal emitting means to respond may be changed by adjustment of a threshold control means.

The emitted signal may be employed to actuate any of a variety of warning devices or to control mechanisms such as valves, etc.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a view in section of a motion sensor forming a part of the apparatus of the present invention.

Figure 2 is a circuit diagram showing the connection of the sensor of Figure 1 to the threshold control means and signal emitting means of the present invention.

The motion sensing apparatus of the present invention includes a novel motion sensor and signal emitting means which comprises threshold control means adjustable to cause the signal emitting means to respond to different magnitudes of motion sensed by the sensor.

As shown in Figure 1, the motion sensor comprises a packing filled container 10 constituting a base adapted for mounting, as by legs 1 Oa, on a platform or device the motion of which is to be sensed. Mounted in the container base 10 by ring 11 is an assembly comprising an opaque inertial element 1 2 disposed within a tubular opaque carrier 1 3 presenting at its lower end an interior concave upper surface 14 in the form of a portion of a sphere provided with a transparent central window 1 5 in its lowest part.

The inertial element 12 is, in the preferred embodiment illustrated and described, a globule of mercury of a size which covers a major part of the area of the window 1 5, but for certain uses it may be desirable to substitute a metal ball for the mercury globule and/or to size the inertial element to entirely cover the window.

The carrier 13 supports at its upper end a closure 1 7 of resilient material such as rubber. The closure 1 7 has a central opening 1 8 seized to receive and retain a light emitting diode 1 9 which, when energized from a source of power 27 via leads 20 to ground (see Figure 2) projects light axially of the carrier 1 3 against the surface 14, window 1 5 and inertial element 12.

Secured to the lower end of the carrier 1 3, preferably removably, is a cup fitting 21 and positioned centrally within it, directly under the window 15, is a phototransistor 22. Its leads 23 pass through a grommeted hole 24 in the cup wall.

This arrangement is such that movement of the platform on which the base 10 is mounted will cause movement of the mercury globule 12 with respect to the window 1 5 and will thus change the amount of light from source 1 9 which reaches the phototransistor 22. This produces a detectable output from the phototransistor which is employed to control signal emitting apparatus.

As shown in Figure 2, the output of the phototransistor 22, which is energized via lead 25 connected through resistor 26 to power supply 27, passes through lead 30 to one input of a comparator 32; the other input of which is connected via lead 33 to the moving contract of a potentiometer 35 the winding of which is connected in series with resistors 36 and 37 of a voltage divider network. The comparator 32 is a differential high gain amplifier which changes its output from high to low when the voltage of its input 30 rises above the voltage of its input 33.

Thus, by adjusting the potentiometer 35 to increase the voltage input via lead 33, a greater voltage input is required on lead 30 to change the output of comparator 32 from high to low. This arrangement, therefore, constitutes a threshold control means whereby the amount of light falling on the phototransistor 22 which is required to produce a change of state of the comparator 32 may be increased or decreased as desired.

Signal emitting means are controlled by the comparator 32 to provide a signal pulse of adjustable duration upon a change of state of the comparator. This means comprises a NOR gate 40 one input of which is connected by lead 41 to the output of comparator 32 and the other input of which is grounded through lead 42. This arrangement is such that when the output of comparator 32 goes from high to low, a pulse is produced at the output of the NOR gate 40.

The output of NOR gate 40 is connected via lead 43 to a monostable or "one-shot" multivibrator 45 which, in response to an input pulse on lead43, emits a pulse on lead 46, the duration of which is controlled by a resistorcapacitance network 48 interposed between the multivibrator 45 and a lead 49 connected via lead 27 to the power supply. The pulse duration may be varied by adjustment of the variable resistor 50, and the limits of its duration established by selecting appropriate values for the resistance and the capacitance employed. The values shown on the drawing for these as well as other components are merely typical values.

Means are provided for selectively determining whether the output pulse of the multivibrator 45 will be employed directly to actuate a device to be controlled by the motion sensing apparatus of the present invention or whether it will be employed to set a switching mechanism from one state to another for actuating such a device. This means comprises a double pole single throw switch 52 which in one position connects its output through resistor 53 via lead 54 directly to the output 46 of multivibrator 45. In its other position switch 52 connects its output via lead 55 to the output of a bistable flipflop 56 which receives its input from the multivibrator 45 via lead 46. A reset switch 60 for flipflop 56 applies an input from the power 27 via leads 49, 61 and 62 to the flipflop to reset it from a high to a low output.

This arrangement is such that, when switch 52 engages the lead 55 contact, an output pulse from the multivibrator 45 will invert the flipflop 56 to maintain an output voltage at the output of switch 52, independently of the initiating pulse, until the reset switch 60 is closed.

In the preferred embodiment illustrated and described the output pulse from switch 52 through resistor 53 is employed to turn on a transistor switching means 65 to apply power from the source 27 via lead 49 to the winding of a solenoid 67 which may actuate any desired type of such device, such as a fluid control valve, or act merely as a relay to control other mechanisms.

While the preferred embodiment of the invention has been described herein, it will be understood that the same is susceptible of modification in many particulars and that the invention is not to be taken as limited to the embodiment illustrated and described.

Claims (11)

1. A motion sensor comprising a substantially opaque inertial element movab!e supported upon a carrier for said element presenting a substantially opaque, concave upper surface having a translucent window area at its lowest part; said inertial element being of such size as to cover at least a portion of said window area, a light source, and a photocell shielded from light other than light from said source; said light source and said photocell being positioned on opposite sides of said window area; whereby upon movement of said inertial element over said window area the amount of light reaching said photocell from said source will be varied.

2. A motion sensor according to claim 1 in which said carrier is in the form of a portion of a sphere.

3. A motion sensor according to claim 1 or claim 2 in which said inertial element is a globule of mercury.

4. Motion sensing apparatus comprising a motion sensor according to any of claims 1 to 3 in combination with signal emitting means including means controlled by said photocell for emitting a signal in response to a change in the amount of light reaching said photocell and means for adjusting said photocell controlled means to vary the sensitivity thereof to changes in the amount of light reaching said photocell.

5. Motion sensing apparatus according to claim 4 in which said photocell controlled means comprises a differential comparator having two inputs, one of said inputs being responsive to the output of said photocell and the other of said inputs including a potentiometer for varying the potential applied thereto.

6. Motion sensing apparatus according to claim 4 in which said photocell controlled means comprises a differential comparator and including a monostable multivibrator controlled by said differential comparator upon a change of state thereof to emit a pulse.

7. Motion sensing apparatus according to claim 6 including means adjustable to vary the duration of a pulse emitted by said multivibrator upon a change of state of said differential comparator.

8. Motion sensing apparatus according to claim 6 or claim 7 including means settable by a pulse emitted by multivibrator to provide a continuous output corresponding to said pulse.

9. Motion sensing apparatus according to claim 6 including means adjustable to vary the duration of a pulse emitted by said multivibrator upon a change of state of said differential comparator, means settable by a pulse emitted by multivibrator to provide a continuous output corresponding to said pulse, and means selectively settable to activate one of said last two named means and to concurrently inactivate the other.

10. A motion sensor according to claim 1 substantially as described herein with reference to and as shown in Fig. 1 of the drawings.

11. A motion sensing apparatus according to claim 6 substantially as described herein with reference to and as shown in the drawings.