GB2188724A

GB2188724A - Ice bin level control

Info

Publication number: GB2188724A
Application number: GB08705896A
Authority: GB
Inventors: Leroy Lind
Original assignee: King Seeley Thermos Co
Current assignee: King Seeley Thermos Co
Priority date: 1986-04-03
Filing date: 1987-03-12
Publication date: 1987-10-07
Also published as: BE1003058A3; AU601413B2; ZA871865B; SE460925B; FR2596857A1; GB2188724B; SE8702772L; JPH0144983B2; MX168749B; GB8705896D0; DE3711241A1; AU7091887A; DE3711241C2; JPS62237264A; CH674074A5; FR2596857B1; IT8719902A0; CA1267203A; IT1202718B; BR8701523A

Description

1 GB2188724A 1 SPECIFICATION tion apparatus 10 is shown which includes an

automatic ice maker device having a discharge Ice bin level sensor port 14. In order for refrigeration apparatus to operate automatically. It is necessary to

Background of the Invention 70 provide some means for controlling the output

This invention relates to an electrical circuit of the ice making device such that it will pro and particularly to one that functions to detect vide ice when desired, but will not overfill ice the amount of ice accumulated in the ice bin bin 16. In accordance with this invention, such of a refrigeration apparatus having an auto- control is provided by an infrared (IR) transmit- matic ice making function. 75 ter 18 and an infrared sensitive photo detec Many modern freezers used in industrial and tor 20 which are mounted to opposing walls residential applications include automatic ice within ice bin 16. When the accumulated pile making systems which deposit ice cubes into of ice cubes is below the line of sight 12 an ice bin for storage. A means for controlling between transmitter 18 and photo detector the output of these types of ice making sys- 80 20, the ice device is actuated to produce ice tems is needed to enable ice being consumed cubes. This action proceeds until the infrared to be replenished and to prevent the mecha- light beam is interrupted, at which time the ice nism from overproducing. Many existing de- making function is caused to cease. Transmit signs for such controls employ means for ter 18 and photo detector 20 are controlled weighing the ice bin or employ paddle-type 85 by ice bin sensor circuit 22. The components sensors which detect the height of the accu- making up ice bin sensor circuit 22 are de mulated pile of the ice cubes. Although these scribed in detail below.

devices generally perform satisfactorily, it is Fig. 2 is a block diagram of the various desirable to provide an improved ice bin level functional sulaparts of circuit 22, whereas- Fig.

sensor which controls an ice making machine 90 3 is a detailed schematic diagram of the cir and operates without moving parts. cuit showing each of the individual compo In accordance with this invention, an ice bin nents. Ice bin sensor circuit 22 is comprised sensor circuit is provided which enables the of three primary circuits: power supply 24, IR detection of the quantity of ice in an ice bin transmitter driver circuit 26, and detector cir using a beam of infrared light which is inter- 95 cuit 28, each of which are preferably mounted rupted when the ice bin is filled to capacity. to a single PC board 34.

The circuit automatically controls the ice mak- As shown in Fig. 3, power supply 24 in ing apparatus to maintain a desired quantity of cludes step-down power transformer 30 available ice cubes. Although light interrupter which is connected to several pins on terminal circuits are well known, the circuit according 100 strip 32 mounted to PC board 34. Power to this invention is efficiently designed for its from step-down transformer 30 is conducted intended function and employs readily available to full wave bridge rectifier 36 where it is and inexpensive components. In order to pre- converted to a DC voltage having an average vent improper operation due to transient inter- value of slightly greater than 12 volts. Filter ruptions of the light beam, the circuit includes 105 capacitors 37 and 38 are used to decrease a time delay function. The circuit further in- the ripple of the rectified signal. Additional fil dudes means for preventing improper oper- tering and voltage control is provided through ation caused by ambient light, and includes a use of IC voltage regulator 40. Diode 41 is mechanism for rapid testing of the circuit dur- provided to inhibit negative going spikes ing production or in-the-field malfunction diag- 110 which may be generated by circuits connected nosis. to power supply 24.

Additional benefits and advantages of the IR driver circuit 26 employs a well-known present invention will become apparent to ---555---timer 42 which, together with addi those skilled in the art to which this invention tional components, is used in circuit 26 as an relates from the subsequent description of the 115 oscillator 44 which operates driver transistor preferred embodiment and the appended 54. Timer 42 functions by monitoring the claims, taken in conjunction with the accom- level of charge of external timing capacitor 46.

panying drawings. The output of timer 42 is high when capacitor 46 is charging which occurs by current flow Brief Description of the Drawings 120 through resistor 48. Diode 50 is provided

Figure 1 is a pictorial view showing a repre- such that the charging of capacitor 46 occurs sentative automatic ice making device; only through resistor 48 by bypassing resistor Figure 2 is a block diagram of the various 52. Once capacitor 46 reaches approximately functional subparts of the circuit according to two-thirds the voltage of the supply, the out this invention; and 125 put of timer 42 becomes low, and the timer Figure 3 is a detailed schematic drawing of switches to a capacitor discharging mode. Dis the circuit according to this invention. charging of capacitor 46 occurs through resis tor 52. The use of diode 50 causes capacitor Detailed Description of the Invention 46 to charge very rapidly and discharge much

With particular reference to Fig. 1, refrigera- 130more slowly. This operation of timer 42 gen- 2 GB2188724A 2 erates a rectangular pulsed output having a indication that ice bin 16 is not filled.

very low percentage duty cycle, i.e. narrow Op amp 96 is employed as a threshold de positive voltage spikes are separated by rela- tector 98 by comparing the signal provided by tively long dwell periods. The output of timer op amp 86 with a reference voltage provided 42 controls the base current of driver transis- 70 by a voltage divider defined by resistors 102 tor 54 through resistor 56. The rectangular and 104. Op amp 96 provides a positive out pulsed output which drives the base of driver put once the difference between the signals transistor 54 switches a twelve volt signal supplied by op amp 86 and the reference sig from power supply 24 to cause current to nal becomes positive. A time delay circuit 106 flow through IR transmitter 18 which is prefer- 75 is defined by resistor 108, capacitor 110 and ably a light emitting diode (LED) and is con- op amp 112. The values of resistor 108 and nected to several pins of terminal strip 32. capacitor 110 are chosen such that the vol LED 58 is also provided as an auxiliary IR tage signal applied to the minus terminal of op transmitter which is mounted on PC board 34 amp 112 changes slowly. When the output of which may be used for future applications but 80 op amp 96 goes positive, time delay circuit is not employed in connection with the pre- 106 causes the input signal to op amp 112 to sent invention. remain below the reference voltage for a pre Detector circuit 28 is comprised of a num- determined period of time, for example, about ber of integrated operational amplifiers (multi- 10 seconds. Similarly, when the output of op purpose analog amplifiers) such as the Na- 85 amp 96 goes negative, the input signal to op tional Semiconductor Model LM 324 having amp 112 remains above the reference voltage four individual operational amplifiers (op amps) for a predetermined time period. When the packaged together. Photo detector 21 pro- signal applied to the minus terminal of op amp vides a variable resistance dependent on its 96 exceeds the reference voltage, a negative exposure to light within its sensitive range. 90 output is provided by op amp 112. Resistor Auxiliary photo detector 20 may be provided 113 is provided for gain control of op amp for future applications. Photo detector 21 pro- 112. Terminal 99 is provided which is con vides a variable current signal which is applied nected to the minus input of op amp 96 and to the inverting (minus) terminal of op amp 60 enables a test signal to be applied to check which functions as a current-to-voltage con- 95 the operation of circuit 22.

vertor 62. The non-inverting (plus) terminal of The signal from the output of op amp 112 op amp 60 is provided with a constant vol- is transmitted to a pair of op amps 114 and tage biasing source of approximately eight 116 which comprise a driver- inverter 118. The volts which is set by the voltage division pro- signal from op amp 112 is divided and ap- vided by resistors 64 and 66. Variations in 100 plied to both negative inputs of op amps 114 current through photo detector 21 caused by and 116 which compare this signal with the exposure to the pulsating light from IR reference signal applied across resistor 104.

transmitter 18 results in op amp 60 providing Op amps 114 and 116 drive relay driver tran a positive going only alternating voltage output sistor 120 through resistors 122 and 124.

signal. Feedback resistor 70 provides gain 105 Transistor 120 controls current flow to relay control for op amp 60. Capacitor 68 acts as 126 which operates the ice making apparatus an ambient light level blocker 72 by removing used with this invention. Diode 128, capacitor DC components from the output of op amp 130 and resistor 132 are provided to dampen which could result, for example, due to electrical noise generated by operation of the constant or low frequency ambient light inputs 110 high inductance relay 126.

to photo detector 21. Capacitor 71 and resis- Ice bin sensor circuit 22, as described tor 80 are provided for, additional signal condi- above, automatically operates an ice making tioning. device by continually monitoring the level of Op amp 74 is used as an amplifier 76 of retained ice and periodically activating and de the signal from capacitor 68, boosting it to a 115 activating the ice maker to maintain a desired desired level using feedback resistor 78. Re- ice supply level. When light from IR transmit sistors 78 and 82 adjust the input levels to ter 18 strikes photo detector 21 for a time op amp 74 to desired magnitudes. Op amps exceeding the time delay, the ice maker is 84 and 86 are configured to provide a peak activated to produce ice. The time delay func detector circuit 88 by employing diodes 90 120 tion prevents inadvertent operation of the ice and 92, capacitor 94 and resistors 91, 93 making device in response to transient expo and 95. The output of peak detector circuit sure of photo detector 21 to light which may 88 is a DC level with some sawtooth rippling occur when ice is being removed from ice bin interposed on it due to charging of capacitor 16. When the ice bin becomes filled, light 94. The output of the peak detector circuit 88 125 from IR transmitter 18 is interrupted. If the from op amp 86 is positive when an alternat- light beam interruption exists for a period of ing signal is received by photo detector 21. time exceeding the time delay, the ice maker When this condition occurs, voltage is sup- is deactivated. The time delay in deactivating plied to LED 96 and through resistor 97 which the ice maker is desirable to avoid response is mounted to PC board 34 to provide an 130 to transient conditions, and also to allow a 3 GB2188724A 3 small degree of overfilling of the ice bin to 4. The electrical circuit according to claim reduce cycling of the system. 1 wherein said current-to-voltage convertor While the above description constitutes the means comprises a first operational amplifier.

preferred embodiments of the present inven- 5. The electrical circuit according to claim tion, it will be appreciated that the invention is 70 2 wherein said direct current blocking means susceptible to modification, variation and comprises a capacitor.

change without departing from the proper 6. The electrical circuit according to claim scope and fair meaning of the accompanying 2 further comprising an amplifier which ampli claims. fies the signal from said direct current block- 75 ing means and provides an amplified signal to

Claims

CLAIMS said peak detector means.

1. An electrical circuit for use in a refrige- 7. The electrical circuit according to claim ration device having an ice making device, an 6 wherein said amplifier is a second opera ice bin for receiving ice produced by said ice tional amplifier.

making device, said electrical circuit controlling 80 8. The electrical circuit according to claim said ice making device to cause said device to 1 further comprising a visible light emitting produce ice when the accumulated ice in said means which is energized by the signal from bin is below a predetermined level, said circuit said peak detector means, thereby providing comprising: an indication that said light sensitive element a light source, 85 is receiving a signal from said light source.

a light sensitive element spaced from said 9. The electrical circuit according to claim light source such that when said ice is above 1 wherein said time delay means comprises a said predetermined level, the light path be- resistor-capacitor network.

tween said light source and said light sensitive 10. The electrical circuit according to claim element is interrupted, said light sensitive ele- 90 1 further comprising a driver inverter which ment producing a current proportional to the receives a signal from said time delay means level of light it receives, and drives a driver transistor which controls current-to-voltage convertor means which said ice maker.

receives a current signal from said light sensi- 11. The electrical circuit according to claim tive element and converts said signal to a vol95 10 wherein said driver transistor provides a tage signal, signal to a relay controlling said ice maker.

peak detector means for detecting the 12. The electrical circuit according to claim peaks of said voltage signal from said current- 1 wherein said peak detector comprises a to-voltage means, third and a fourth operational amplifier.

threshold detector means for passing the 100 13. The electrical circuit according to claim signal from said peak detector means only if 1 wherein said threshold detector comprises a said signal exceeds a predetermined threshold, fifth operational amplifier.

and 14. The electrical circuit according to claim time delay means which provides an output 9 wherein said time delay means further com- which controls said ice making apparatus only 105 prises a sixth operational amplifier.

after the signal from said threshold detector 15. The electrical circuit according to claim means exists for at least a first predetermined 10 wherein said driver- inverter comprises a time duration, such that when said ice is be- seventh and an eighth operational amplifier.

low said predetermined level for said first pre- 16. The electrical circuit according to claim determined time duration, said time delay 110 1 wherein said first and second determined means activates said ice making apparatus, time durations are approximately equal.

said time delay means further maintaining said 17. An electrical circuit for use in a refrige output until said signal from said threshold deration device having an ice making device, an tector does not exist for a second predeter- ice bin for receiving ice produced by said ice mined time duration, such that when said ice 115 making device, said electrical circuit controlling is above said predetermined level for said sec- said ice making device to cause said device to ond predetermined time period, said time de- produce ice when the accumulated ice in said lay means deactivates said ice making appara- bin is below a predetermined level, said circuit tus. comprising:

2. The electrical circuit according to claim 120 a light emitting diode light source which 1 further comprising an oscillator for driving produces light of infrared frequencies, said light source to produce a pulsed light a first drive transistor controlling current output and direct current blocking means for flow to said light source, receiving said voltage signal from said current- an oscillator driving said first driver transisto-voltage convertor means and passes only 125 tor to control said first driver transistor to alternating voltage components, thereby func- produce a pulsed light output, tioning as an ambient light level blocker. a photo detector spaced from said light 3. The electrical circuit according to claim source such that when said ice is above said 1 wherein said light source generates infrared predetermined level, the light path between frequency light. 130 said light source and said photo detector is 4 GB2188724A 4 interrupted, said photo detector producing a Printed for Her Majesty's Stationery Office current proportional to the level of light it re- by Burgess & Son (Abingdon) Ltd, Did 8991685, 1987.

ceives, Published at The Patent Office, 25 Southampton Buildings, a first operational amplifier operating as a London, WC2A 'I AY, from which copies may be obtained.

current-to-voltage convertor which receives a current signal from said photo detector and converts said signal to a voltage signal, a capacitor coupled to the output of said first operational amplifier thereby passing only alternating voltage signal components and functioning as an ambient light level blocker, a second operational amplifier for amplifying the signal from said capacitor, third and fourth operational amplifiers coup led to a pair of diodes functioning as a peak Y detector for detecting the peaks of said signal from said second operational amplifier, a fifth operational amplifier coupled to said fourth operational amplifier and functioning as a threshold detector for passing the signal from said fourth operational amplifier only if said signal exceeds a predetermined threshold, a time delay means including a resistor capacitor network and a sixth operational am plifier which provides an output after the sig nal from said fifth operational amplifier exists for at least a first predetermined time dura tion, and continues to provide said output until said signal from said fifth operational amplifier is interrupted for at least a second predeter mined time duration, a driver including a seventh operational am plifier which receives a signal from said sixth operational amplifier, a relay driver transistor controlled by said seventh operational amplifier, and a relay coupled to said relay driver transistor whereby when said ice is below said predetermined level for said first predetermined time duration, said relay driver transistor actuates said relay and said ice 'making apparatus to produce ice and when said ice is above said predetermined level for said second predetermined time duration, said relay driver transis- tor deactivates said relay and said ice making apparatus.

18. The electrical circuit according to claim 17 further comprising an eighth operational amplifier connected in parallel with said sev- enth operational amplifier and operating with said seventh operational amplifier to control said second driver transistor.

19. The electrical circuit according to claim 17 wherein said first and second predeter- mined time durations are approximately equal.

20. An electrical circuit for use in a refrigeration device, such electrical circuit being constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

21. A refrigeration device including an electrical circuit in accordance with any preceding claims.