GB2172399A - Device for converting cyclic motion into digital output - Google Patents

Abstract

The proposed device comprises at least one sensor 18 and a computing/display package 22. The sensor detects complete cycles of cyclic, motions, and the computing/display package converts the signals into desired digital information and displays aid information. A flying lead as 28 is used to connect the sensor 18 to the package 22. The sensors 18 are positioned to detect the cyclic motion of pointers or discs of gas and/or electricity meters. The sensors may photoelectrically detect a pointer, line or other marking and may use yellow or IR light which is preferably modulated. Alternatively, detection may be capacitative or inductive. The computing package is employed to evaluate the amount of gas or electricity used or a prediction of the amount that will be used in any period and/or the cost thereof. The shape of the sensor (two concentric arcuate boundaries) provide ease of fitting in position with accuracy. Self adhesive material is employed to locate it in place. <IMAGE>

Description

SPECIFICATION Device for converting cyclic motion into digital output This invention concerns a device for converting cyclic motion into a digital output according to the number of complete said motions.

The term cyclic motion is intended to include motion of, for example, a dial pointer, a spinning disc or a rotating cylinder as well as pendulum type motions.

The object of the invention is to provide a device for converting cyclic motions into a digital output according to the number of complete said motions.

According to the invention there is provided a device for converting cyclic motions into a digital output according to the number of complete said motions, comprising means for detecting complete said motions to give signals, means for converting the signals into desired digital information and means for displaying said information.

Various means may be used for detecting the cyclic motions. One proposal is to detect a mechanical indication of the motion at one or more points in a cycle by a differential refelctive system using a light emitter and sensor. Alternatively detection could be by a capacitive or inductive proximity sensor.

The detection means produces signals that are converted into desired information preferably by computing means for mathematically manipulating the signals into the desired information. The computing means may count the signals absolutely or per unit time or convert the signals into any desired form, possibly using additional input information.

The device of the invention preferably also includes computing means in order to enhance detection of the cyclic motions in preferance to background and fluctuating ambient signals.

The digital information may be displayed in any desired way, such as by outputting to a numeric or alphanumeric display, for example light emitting diodes, liquid crystal or via an interface to some other external device.

The device of the invention is particularly useful in connection with meters for gas and electricity supplies. Gas meters usually have dials with rotating pointers and electricity meters usually have spinning discs. The device of the invention can, therefore, be used to detect rotation of the pointers or of a mark, say black, on the edge of the disc and so count the number of revolutions of the pointers or disc over a period of time. The signals obtained can be used to provide a wide range of information, particularly related to costs incurred by the use of the gas or electricity.For example the following information could be provided by the device of the invention: a) total spend from zero time; b) total spend in last 24 hour period; c) total spend in last 7 day period; d) total spend in last 13 week period; e) average daily spend since zero time; f) projected spend over 13 weeks period; g) spend between two points in time selected as desired manually.

Clearly, many other types of information may be provided by the device of the invention depending on the programming of the computing means.

Means for inputting additional information to the device may be provided for calibration andlor to control the device for its particulartask, input time data, instruct the device in any way desired, stop, start, and recall functions or to perform any other input requirements.

In a preferred form the device of the invention comprises a sensor that can be held in a position to detect each time a pointer or a mark on the edge of a disc passes, the sensor being part of or connected to a computing/display package powered either by mains elctricity or by battery.

The sensor preferably has means for holding it rigidly in proximity to the pointer or disc to detect the movement thereof. Many meters have glass or plastics covers over the pointers or discs. It would, therefore, be convenient to provide the sensor with, for example, self-adhesive tape for adherence.

Alternative holding means may include magnetic means or mechanical fixing means.

For a remote sensor, connection to the package may be by any suitable means, such as flying leads or infra red radiation or ultrasonic transmission.

The device of the invention may also have means by which an operator can position the sensor so as to obtain an optimum signal from the subject being detected. Conveniently the sensor may be in the form of a ring through whose opening the desired location of the sensor can be seen.

In a preferred embodiment, the sensor uses a pulsed yellow emitter to irradiate an area of the meter face through which the meter pointer or disc passes. A pulsed signal, at typically 1kHz, is used to enable the detector to substantially reject ambient light variations. A yellow emitter is used to increase the contrast variation seen by the detector when detecting red pointers or marks, the reflected radiation is detected by a sensitive photo transistor. As the pointer or mark on the edge of a disc passes through the irradiated area, the intensity of the reflected radiation is changed and thus the intensity of the recovered pulsed signal. The phototransistor device produces a current proportional to the incident light energy.The current is passed through a resistor and the alternating current component of the resultant voltage is amplified and filtered in a bandpass amplifier to reject extraneous signals. The amplified signal is rectified and compared with a linear ramp produced via a constant current source and capacitor network controlled from a microprocessor. The output of the comparator is monitored by the microprocessor and the time taken from the start of the ramp till the comparator output changes state is used as a measure of the recovered pulsed signal and thus the reflected light intensity.

This time value is generated repeatedly at a fast enough rate to ensure detection of the pointer or mark when moving at its maximum velocity. These readings are then passed through a software algorithn which determines if a pointer or mark passes the detector and generates an event. The software algorithn automatically compensates for the large variations in pointer or mark velocities experienced.

According to another embodiment, the sensor uses an infra red emitter to irradiate an area of the meter face through which the meter pointer or disc passes. The reflected radiation is detected by infra red sensitive photo transistor. As the pointer or mark on the edge of a disc passes through the irradiated area, the intensity of the reflected radiation is changed. The photo transistor produces a current proportional to the incident light-energy. This device produces a current proportional to the incident light energy. The current is passed through a resistor and the resultant voltage is compared with an exponential ramp produced via an R/C network from a square wave pulse generated by a microprocessor.The output of the comparator is monitored by the micro-processor and the time taken from the start of the pulse for the comparatoroutputto change state is used as a measure of reflected light intensity. This time value is generated repeatedly at a fast enough rate to ensure detection of the fastest possible pointer velocity, and average of 3 or more readings is computed and then compared with the next calculated average if the difference between those two values is greater than an amount (determined by experiment) then an event is said to have occurred.

This event is used as the basis of all the subsequent calculations i.e. spend, projected spend etc. by scaling the event by the calibration factor of the particular meter.

The microprocessor can also control a LED display, say an eight digit display, and a keyboard by means of a simple multiplexing technique. The component parts of the unit will be; emitter, detector, filter/amplifier, detector comparator, microprocessor, display assembly, keyboard and battery supply.

This invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a device of the invention on both an electricity meter and on a gas meter; Figure 2 sjows a sensor of the device of the invention, Figures 3 and 4 are front view and side view of one embodiment of computing package, Figures Sand 6 are the front view and side view of another embodiment of sensor, and Figures 7a, b and c show positioning of the sensor on different types of meter.

Referring firstly to the drawings of figures 1 and 2, a gas meter 10 has a window 12 through which a numerical display 14 of the units of gas consumed is visible. The display 14 includes a rotating pointer dial 16. At a position on the dial part which the pointer passes is fixed as light reflective sensor 18.

The sensor 18 is connected via flying lead 20 to a display and computing package 22.

The package 22 has a display window 24 using for example light emitting diodes or a liquid crystal to show the desired information. A series of function buttons 26 are provided for selection of the information to be displayed.

The display/computing package is also shown connected by flying lead 28 to another sensor 18 on the display window 32 of an electricity meter 34. This meter has a spinning disc 36 that indicates units of electricity consumed according to the number of times a mark 38 on the edge of the disc completes a revolution. The sensor 18 is positioned to detect the passing of the mark 38.

In more detail, the sensors 18 have a ring-like body 40 with a central aperture 41 to assist positioning visually on the meter window, as shown over the axis of rotation of a pointer 45. The body 40 has on one side a self-adhesive pad 42 to hold it on the meter window. In the same side of the body is an emitter and sensor 44. This may be infra red or any other colour/wavelength as convenient. We prefer to use yellow light, thus radiation is emitted continuously and the reflected radiation is continually monitored. However, as the pointer or mark passes through the irradiated area, the reflected radiation changes in intensity. This change in intensity is used to produce a pulse signal. The signal is then converted in the display computing package into the desired information.

Another embodiment of the two units of the device are described with reference to Figures 3 and 4 which illustrate the main body 22', and Figures 5 and 6which illustrate a sensing head 18' containing the LED and detection with a self adhesive surface 51 for attachment to the meter window. The main body contains the microprocessor, PCB, display, keyboard entry and batteries. The stethoscope type sensing head and separate main body allows maximum flexibility for the user to position the read-out in a convenient place. It also enables the sensing head to be positioned accurately on the meter, the aperture 61 for the cable connection to the main body is illustrated in Figures 5 and 6.

The shape of the sensing head comprising two concentric semi-circular surfaces 53, 55 and the surfaces 57 or a cord and meter, serve to assist/ enable the end user to position the sensor accurately on the meter. Positioning lines 59 are also provided to assist. Figures 7a, b and c show how the surfaces/lines 55, 53, 57 can be used respectively to accurately position the sensor for different types of meter with different sizes of dial (Figures 7a and b) on the disc type (7c)).

The sensor head uses a yellow high efficiency LED such as that manufactured by Hewlet Parkard to illuminate the face of the dial and a photo transistor, such as that manufactured by ISOCOM, to monitor the return signal. Ambient light variations are taken care of by pulsing the LED at a frequency of 1 kHz (this also reduces the power consumption). Other frequencies may be employed with similar effect.

The return signal is monitored for the pulsed frequency only. The drive signal for the LED is derived from the micro processor and is ultimately controlled by a ceramic resonator which provides the clock for the microprocessor.

A filter-amplifier stage consisting of a 1 kHz bandpass filter constructed from two operational amplifiers from a BIFET quad amplifier is employed and to convert the recovered AC signal to DC signal which can be monitored by the A/D converter, a precision rectifier with gain employed.

Due to the software drift convertion techniques employed to single slope A/D converter can be used with a 1 in 256 resolution. In operation, a transistor is switched on to discharge a capacitor until a conversion is required, then the transistor is switched off.

The voltage across the capacitor rises, linearly, to a predetermined voltage the time which it takes from the output of the comparator (which is monitored by the microprocessor) to change state from the stack of the conversion is measured by the microprocessor and this is directly proportional to the applied voltage and hence to the detected light level.

The microprocessor has to run continuously, so low power consumption is important, and it must also be capable of driving the required display. A four digit LED display 63 is preferred although an LCD display may present a desirable alternative. The LED display has obvious advantages in low light environments, but would usually only be illuminated on demand.

A minimum of four digits is required to display all the necessary information. In order to keep costs as low as possible, a very simple user interface 64 is proposed, consisting of three keys 65, 67, 69; two buttons 65, 67 to be used for UP and DOWN commands and the third 69 for COMMAND. For example, the display on the unit will usually be off, and to select a particular function, the COMMAND key is pressed. The display will then show a number which will count from say 1 to 9; the function is selected by releasing the COMMAND key when the particular function number desired is reached values are entered into the device by pressing the UP and DOWN keys. The main body can be provided with a fixing clip 71 as illustrated.

Claims (16)

1. A device for converting cyclic motions into a digital output according to the number of complete said motions, comprising means for detecting complete said motions to give signals, means for converting the signals into desired digital information and meansfordisplaying said information.

2. A device as claimed in claim 1 in which a mechanical indication ofthe motion at one or more points in the cycle is detected by a differential refelctive system using a light emitter and sensor.

3. A device as claimed in claim 2 in which a pulsed yellow emitter is used.

4. A device as claimed in claim 2 in which an infra red emitter is used.

5. A device as claimed in claim 1 in which a mechanical indication of the motion at one or more points in the cycle is detected by a capacitive or indicative proximity sensor.

6. A device as claimed in any one of claims 1 to 5 in which the detection means produces signals that are converted into desired information by computing means.

7. A device as claimed in any one of claims 1 to 6 in which computing means is provided in order to enhance detection of the cyclic motions in preference to background and fluctuating ambient signals.

8. A device as claimed in any preceding claim in which the digital information is displayed by outputting to a numeric or alpha numeric display.

9. A device as claimed in any preceding claim in which the cyclic motions are those of a rotating pointer of a dial or a point on a rotating disc of a gas meter or electricity meter.

10. A device as claimed in any preceding claim in which the detecting means comprises a sensor that can be held in a position to detect said cyclic motions, the sensor being part of or connected to a computing/display package.

11. A device as claimed in claim 10 in which the sensor has means for holding it rigidly in proximity to the cyclical member to detect movement thereof.

12. A device as claimed in claim 11 in which a self-adhesive material is employed.

13. A device as claimed in claim 8,10,11 or 12 in which the sensor is connected to the package by means of flying leads or infra red radiation or ultrasonic transmission.

14. A device as claimed in any of claim 10 to 13 in which the sensor is in the form of a ring through whose opening the desired location of the sensor can be seen.

15. A device as claimed in any of claims lotto 13 in which the sensor has two or more concentric arcuate surfaces or positioning lines and a cordal positioning line or surface therebetween to assist in positioning the sensor in the desired location.

16. A device for converting cyclic motions into a digital output substantially as hereinbefore described with reference to and as illustrated in any of the accompanying drawings.