Ice bin level sensor with time delay

• US 4,822,996 A
• Filed: 06/03/1988
• Issued: 04/18/1989
• Est. Priority Date: 04/03/1986
• Status: Expired due to Term

• Current Assignee: Thermos LLC
• Original Assignee: Thermos LLC
• Inventors: Lind, LeRoy
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): Messinger, Michael
• Application Number:
  US07/205,608
• Time in Patent Office: 319 Days
• Field of Search: 62/137, 250/221, 250/222.1, 250/223 R, 340/583
• US Class Current: 250/222.1
• CPC Class Codes: F25C 5/187 with ice level sensing means
• CPC Class Codes: G01F 23/2921 for discrete levels
• CPC Class Codes: G05D 9/12 characterised by the use of electric means

Abstract

A circuit for controlling an automatic ice making system of a refrigeration apparatus. The device includes an electrical circuit which operates the ice making machine using a light interrupter system. A plused light source is placed such that it will be interfered when the ice has reached a predetermined level in the ice containing bin. The circuit uses operational amplifier signal processing components which activate the ice making machine once the light source is sensed for a predetermined period of time and deactivates the ice maker when the light source is not sensed for another predetermined period of time. The circuit also includes means for eliminating the effect of ambient lights.

Claims

1. An electrical circuit for use in a refrigeration device having an ice making device, an ice bin for receiving ice produced by said ice making device, said electrical circuit controlling said ice making device to cause said device to provide ice when the accumulated ice in said bin is below a predetermined level said circuit comprising:

a light source,

a light sensitive element spaced from said light source such that when said ice is above said predetermined level, the light path between said light source and said light sensitive element is interrupted, said light sensitive element producing a current proportional to the level of light it receives,

current-to-voltage convertor means which receives a current signal from said light sensitive element and converts said signal to a voltage signal,

peak detector means comprising at least one first operational amplifier having at least one diode providing feedback to said operational amplifier for detecting the peaks of said voltage signal from said current-to-voltage means,

threshold detector means comprising at least one second operational amplifier for passing the signal from said peak detector means only if said signal exceeds a predetermined threshold, and

time delay means which provides an output which controls said ice making device only after the signal from said threshold detector means exists for at least a first predetermined time duration, such that when said ice is below said predetermined level for said first predetermined time duration, said time delay means activates said ice making device, said time delay means further maintaining said output until said signal from said threshold detector does not exist for a second predetermined time duration, such that when said ice is above said predetermined level for said second predetermined time period, said time delay means deactivates said ice making device,

said time delay means comprising at least one third operational amplififier having an input and at least one resistor and capacitor circuit connected to the input of said third operational amplifier, said resistor and capacitor circuit also being connected to said threshold detector and defining a time constant which in turn defines both said first and said second predetermined time durations,

wherein said time constant is selected such that the discharge of ice from said ice making device does not deactivate said ice making device if the level in said bin is below said predetermined level, and

wherein said time constant is further selected such that the momentary displacement of ice in said bin during vending will not activate said ice making device.

2. The electrical circuit according to claim 1 further comprising an oscillator for driving said light source to produce a pulsed light output and direct current blocking means for receiving said voltage signal from said current-to-voltage convertor means and passes only alternating voltage components, thereby functioning as an ambient light level blocker.

3. The electrical circuit according to claim 1 wherein said light source generates infrared frequency light.

4. The electrical circuit according to claim 1 wherein said current-to-voltage convertor means comprises a first operational amplifier.

5. The electrical circuit according to claim 2 wherein said direct current blocking means comprises a capacitor.

6. The electrical circuit according to claim 2 further comprising an amplifier which amplifies the signal from said direct current blocking means and provides an amplified signal to said peak detector means.

7. The electrical circuit according to claim 6 wherein said amplifier is a second operational amplifier.

8. The electrical circuit according to claim 1 further comprising a visible light emitting means which is energized by the signal from said peak detector means, thereby providing an indication that said light sensitive element is receiving a signal from said light source.

9. The electrical circuit according to claim 1 wherein said time delay means comprises a resistor-capacitor network.

10. The electrical circuit according to claim 1 further comprising a driver inverter which receives a signal from said time delay means and drives a driver transistor which controls said ice maker.

11. The electrical circuit according to claim 10 wherein said driver transistor provides a signal to a relay controlling said ice maker.

12. The electrical circuit according to claim 1 wherein said peak detector comprises a third and a fourth operational amplifier.

13. The electrical circuit according to claim 1 wherein said threshold detector comprises a fifth operational amplifier.

14. The electrical circuit according to claim 9 wherein said time delay means further comprises a sixth operational amplifier.

15. The electrical circuit according to claim 10 wherein said driver-inverter comprises a seventh and an eighth operational amplifier.

16. The electrical circuit according to claim 1 wherein said first and second determined time durations are approximately equal.

17. An electrical circuit for use in a refrigeration device having an ice making device, an ice bin for receiving ice produced by said ice making device, said electrical circuit controlling said ice making device to cause said device to produce ice when the accumulated ice in said bin is below a predetermined level, said circuit comprising:

a light emitting diode light source which produces light of infrared frequencies,

a first driver transistor controlling current flow to said light source,

an oscillator driving said first driver transistor to control said first driver transistor to produce a pulsed light output,

a photo detector spaced from said light source such that when said ice is above said predetermined level, the light path between said light source and said photo detector is interrupted, said photo detector producing a current proportional to the level of light it receives,

a first operational amplifier operating as a 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 coupled to a pair of diodes functioning as a peak 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 amplifier which provides an output after the signal from said fifth operational amplifier exists for at least a first predetermined time duration, and continues to provide said output until said signal from said fifth operational amplifier is interrupted for at least a second predetermined time duration,

a driver including a seventh operational amplifier 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 transistor 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 seventh 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 predetermined time durations are approximately equal.